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1199 lines
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1199 lines
60 KiB
XML
5 years ago
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<appendix xmlns="http://docbook.org/ns/docbook"
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7 years ago
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xmlns:xl="http://www.w3.org/1999/xlink" version="5.0" xml:lang="en" xml:id="dbdoclet.50569379_75285">
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<title>A Protocol for VSCSI Communications</title>
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<section>
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<title>Introduction</title>
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5 years ago
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<para>The purpose of this appendix is to define the protocol used by
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7 years ago
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virtual SCSI (vscsi) client drivers and vscsi server drivers in sufficient
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detail to ensure compatibility between unlike operating systems
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implementing these features. The SCSI Architecture Model (SAM-2) defines
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the following simplified abstract model and terminology for a SCSI
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system.</para>
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<para />
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<figure xml:id="dbdoclet.50569379_57878">
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<title>SCSI Initiator/Target Architecture</title>
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<mediaobject>
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<imageobject role="html">
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<imagedata fileref="figures/PAPR-66.gif" format="GIF" scalefit="1" />
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</imageobject>
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<imageobject role="fo">
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<imagedata contentdepth="100%" fileref="figures/PAPR-66.gif"
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format="GIF" scalefit="1" width="100%" />
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</imageobject>
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</mediaobject>
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</figure>
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<para>In <xref linkend="dbdoclet.50569379_57878" />, the Application Client is the
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application producing or consuming the data being stored. The SCSI
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Initiator Port is the virtual scsi client adapter running in the client
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partition. The Service Delivery System is the Hypervisor. The SCSI Target
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Port is the vscsi host (vhost) adapter running in the VIO server (VIOS).
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The Logical Unit is the entity providing the data storage
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services.</para>
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<para>Note that the model is not symmetrical. Client adapters may
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communicate only with host adapters and host adapters may communicate
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only with client adapters. Each may communicate with a maximum of one
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partner at any point in time. Client adapters may exist only in client
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partitions. Host adapters may exist only in VIOSs. A client partition may
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have multiple client adapters and they may communicate with host adapters
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in the same or different VIOSs. A SCSI host adapter may have multiple
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Logical Units defined to it for use. Almost all messages are initiated by
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the client. The client and host adapters communicate using
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Command/Response Queues (CRQ) defined earlier in this document. A client
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may not read or write VIOS memory, it may only write to the VIOS CRQ. The
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VIOS may read and write to client partition memory, if the client passes
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the VIOS a DMA mapped address for that memory.</para>
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</section>
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<section>
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<title>SCSI Remote DMA Protocol (SRP)</title>
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<para>The protocol used for transferring data between the application
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client and the logical unit is the SCSI Remote DMA Protocol (SRP), revision
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16.a, as defined by the InterNational Committee for Information Technology
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Standards (INCITS). Copies of the standard are available at the INCITS
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website at T10.org.</para>
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<para>The client builds an SRP request in its address space, then DMA maps
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that request so that the VIOS can access it. The client notifies the VIOS
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of the request by including that mapped address in a CRQ message. A SCSI
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Command Data Block (CDB) is encapsulated within the SRP request. Also
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within the SRP request is a tag field, which is private to the client. The
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VIOS must not modify that tag value in any way. When the request is
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complete, the VIOS notifies the client of the completion by including that
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tag field in the CRQ message to the client. The client then uses that tag
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value to locate the request being completed.</para>
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<para>If the SRP request expects to transfer any data, it also contains one
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of the two types of memory descriptors specified by the SRP standard, to
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describe the buffer(s) to be used in the data transfer. In the SRP memory
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descriptor, the virtual address field is the DMA mapped address of the
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buffer, to be used by the VIOS to transfer the data. The memory handle
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field is not used and should be initialized to zero.</para>
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<para>Using the H_SEND_CRQ call, the client sends the SRP request to the
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VIOS. The first 64 bits of the message describe the type of message, the
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format, and the length. The second 64 bits of the CRQ message contain the
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DMA mapped address of the SRP request in the client partition memory. The
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H_SEND_CRQ call in the client generates a virtual interrupt in the VIOS, if
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the CRQ is going from empty to non-empty (edge-triggered interrupt).</para>
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<para>The vhost driver uses the H_COPY_RDMA call and the mapped address to
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copy the SRP request from client partition memory into VIOS memory,
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examines the LUN to which the request is addressed, builds the appropriate
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structure to represent the request, according to the type of backing
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device, then queues the request to the backing device. The backing device
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may be an actual physical storage device, a software emulator, or some
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combination of device and emulation.</para>
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<para>In the request is an SRP memory descriptor which contains one or more
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address/length pairs describing one or more buffers in client partition
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memory address space. The memory handle field of the SRP memory descriptor
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is not used by vscsi and should be initialized to zero. The virtual address
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field in the SRP memory descriptor is the DMA mapped address of a buffer in
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client partition memory that the backing device uses to transfer data. When
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the backing device services the request, it uses the same DMA services as
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it would to handle a request that had originated locally on the VIOS.
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However, DMA services on the VIOS use the H_COPY_RDMA call and the mapped
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address(es) in the SRP memory descriptor(s) to copy data directly between
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the client partition and the device, transparent to the device.</para>
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<para>When the backing device has completed the request, it returns the
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request along with the results back to the VIOS driver. The VIOS driver
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builds an SRP response structure and copies that response back into client
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partition memory over the original SRP request. The SRP response includes
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any sense data that may have been returned with the request. All virtual
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devices are “auto-sense” devices. The vhost driver then
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notifies the client partition of the completed request by using H_SEND_CRQ
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to place a message in the client CRQ. The first 64 bits of the message
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describe the type, format, and length of the message. The second 64 bits
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are the “tag” field from the original SRP request. The client
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uses the tag to locate the SRP response and processes the response as
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appropriate.</para>
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<para>It is important to note that the client partition must not unmap or
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modify in any way any of the memory associated with the request between the
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time that it notifies the VIOS of the request and the time that the VIOS
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notifies the client of the response.</para>
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</section>
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<section>
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<title>Connection Establishment</title>
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<para>Before any data can be transferred the two partitions have to
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establish a connection. Each partition is required to use H_REG_CRQ to
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register a Command/Response Queue (CRQ) with the Hypervisor to receive
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messages from the other partition. The size of the queue must be a multiple
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of 4KB. That memory must be DMA mapped. The size of the CRQ merely
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determines the number of requests that a client may send to the VIOS in a
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single burst. The VIOS dequeues the requests as soon as it can, so in
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evenly balanced systems, where the VIOS has enough CPUs and memory to deal
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with all of its clients, the size of the CRQ is not a major limiting
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factor.</para>
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<para>After H_REG_CRQ returns H_SUCCESS, each partition uses H_SEND_CRQ to
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attempt to send the Initialization message described previously in this
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document. This is a race condition that only one partition will win. The
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first partition to send the Initialization message receives an H_CLOSED
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return value from the Hypervisor, because the other partition has not yet
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registered its queue. The winning partition must wait to receive the
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Initialization message from its partner. The second partition to send the
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Initialization message receives an H_SUCCESS return value from the
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Hypervisor. That partition must wait for the Initialization Complete
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message from its partner. When a partition receives an Initialization
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message during connection establishment, it must respond with the
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Initialization Complete message and may then proceed to the next step. When
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a partition receives the Initialization Complete message during connection
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establishment, it may then proceed to the next step.</para>
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<para>The next step in connection establishment is for the client to send
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one or more of the Management Datagrams (MAD) messages, described in detail
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later in this chapter. Since this is before the completion of the SRP
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Login request, no flow control has been established between the client and
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VIOS, so the client may send only one message at a time and must wait for
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the response from the VIOS before sending the next one. The exception is
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the optional MAD_EMPY_IU message. The client may follow that immediately
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with another message. The VIOS enforces flow control violations by logging
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and informative error, then closing and reopening the CRQ.</para>
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<para>The client is required to send the MAD_ADAPTER_INFO_REQUEST. This
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provides the information that the VIOS displays with the lsmap command. The
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client may find it useful to save off and display the information that the
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VIOS returns in the response to the MAD_ADAPTER_INFO_REQUEST. Customers and
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service personnel frequently find this kind of information useful in
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unravelling some of the more elaborate configurations.</para>
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<para>The client is required to send the MAD_CAPABILITIES_EXCHANGE if it
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wishes to participate in Partition Mobility operations. If it does not send
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this message, the VIOS does not consider it to be capable of being
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migrated.</para>
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<para>If the client wishes to take advantage of the “fast fail”
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feature, it should send the MAD_ENABLE_FAST_FAIL message before the SRP
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login request.</para>
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<para>The last step in connection establishment is the SRP login request.
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The Target Port Identifier field of the SRP Login request is not used by
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vscsi and should be initialized to zero. The client uses the SRP login
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request to specify the size of the largest SRP Information Unit that it
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will send to the VIOS and the format of the type of memory descriptors it
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intends to use. The size of the largest SRP Information Unit must also
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account for the size of the largest Management Datagram that the client
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expects to send. The VIOS may reject the SRP login if it cannot support the
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requested options. The VIOS will delay sending the response to the SRP
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login if it does not have any LUNs defined to it yet. This may be the case
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if both partitions are booted simultaneously and the VIOS has not completed
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the configuration process when the client sends the SRP login.</para>
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<para>If the VIOS accepts the SRP login, it sends the SRP login response
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and notifies the client of this by placing the tag value from the SRP Login
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in the CRQ message. The request limit delta field of the SRP login response
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contains the maximum number of requests that the VIOS will allow the client
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to have active on the VIOS at any one time. This is the flow control
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mechanism. If the client violates this limit by sending too many requests,
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the VIOS will terminate the connection to the client. Note that each SRP
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response message also contains a request limit delta field. Typically, this
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is set to 1, to indicate that this completed request means another can be
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initiated. But if the VIOS has substantial resources added to it, it may
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increase the number of requests a client may have active, and will do so by
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setting a value greater than one in this field. Once the SRP login has been
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accepted, the VIOS may increase the number of requests, but it may never
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decrease that number until this connection is terminated.</para>
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<para>After receiving an SRP Login Response for the VIOS, the client may
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then proceed with normal I/O data traffic. Usually, this starts with device
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discovery, where the client sends a REPORT_LUNS SCSI request to the VIOS.
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The VIOS responds with the list of LUNs that have been defined to this host
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adapter. The client may then use other SCSI requests to determine the
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identity and capabilities of each LUN.</para>
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<para>If, after establishing a connection (VIOS sends SRP login response,
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and client receives it), a partition receives another Initialization
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message, Initialization Complete message, an SRP Login, or SRP Login
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response without some indication that the connection has been terminated,
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usually a Transport Event (described later), that is a protocol violation.
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Protocol violations are handled by logging an error, then closing and
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reopening the CRQ.</para>
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<para>Likewise, after a connection has been terminated, the first messages
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must be either the Initialization or the Initialization Complete messages,
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as appropriate. Any other message is a protocol violation. And any SRP
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message received before a successful SRP Login is a protocol
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violation.</para>
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</section>
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<section>
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<title>Connection Termination</title>
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<para>A connection may be terminated by the client sending the VIOS an
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SRP_I_LOGOUT Information Unit. The VIOS may send the client an SRP_T_LOGOUT
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Information Unit, but only if the client has provided resources for this by
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sending the MAD EMPTY IU first. In the current implementation, neither is
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used and the drivers just call H_FREE_CRQ to terminate the
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connection.</para>
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<para>A connection may also be terminated by the abnormal termination of a
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partition. When a partition crashes, the Hypervisor invalidates all of the
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memory mappings for that partition and places a Transport Event in the CRQ
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of the partner. If the partition that crashed was a client with requests
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active on the VIOS, when the storage drivers attempt to service those
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“in flight” requests, they find that the DMA mappings
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associated with the requests are no longer valid and usually will log one
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or more errors to that effect.</para>
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<para>When a partition calls H_FREE_CRQ or crashes, the Hypervisor notifies
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the partner partition by placing a Transport Event in the partner’s
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CRQ. The first byte of the Transport Event is set to 0xFF, to indicate that
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this is a Transport Event. The second byte describes the event. A value of
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0x01 indicates that the partner partition failed (crashed). A value of 0x02
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indicates that the partner partition called H_FREE_CRQ. A value of 0x06
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indicates to a client that it has been migrated. Only clients that send the
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MAD_CAPABILITIES message are candidates for being migrated. A VIOS cannot
|
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be migrated.</para>
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<para>When a partition receives a Transport Event, it is not required to
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close its CRQ. It may instead just wait for an Initialization message from
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the partner partition when it is ready to communicate again.</para>
|
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</section>
|
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<section>
|
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<title>Client Migration</title>
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<para>When a client receives the migrated Transport Event, it must unmap
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any memory associated with any requests currently active on the VIOS. The
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client will never receive any completions for those requests and must remap
|
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and restart them at the end of the migration. Then the client must call
|
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H_ENABLE_CRQ until it returns H_SUCCESS. When the CRQ has been successfully
|
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enabled, the client sends the Initialization message and waits for the
|
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Initialization Complete message. It then goes through the rest of the
|
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connection establishment process, followed by the SRP login. After the VIOS
|
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sends the SRP Login response, the client may resume normal data transfers,
|
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starting with any requests that may have been active on the VIOS when the
|
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client was migrated.</para>
|
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<para>Note that the partition identification information that the client
|
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sends in the MAD_ADAPTER_INFO message immediately after the migration event
|
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may be stale and reflect the identification of the original client
|
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partition before the migration. A client may register for DLPAR
|
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notification of migration, use that notification to obtain the current
|
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partition identification, and send another MAD_ADAPTER_INFO message to the
|
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|
VIOS with the correct information.</para>
|
||
|
</section>
|
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|
<section>
|
||
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<title>VSCSI Message Formats</title>
|
||
|
<para>All virtual scsi communications between client and server occurs
|
||
|
using the Reliable Command/Response Transport and Logical Remote DMA
|
||
|
functions defined earlier in this document. No other channels of
|
||
|
communication are required to perform virtual SCSI functions.</para>
|
||
|
<para>These communications are made up of three classes of messages:</para>
|
||
|
|
||
5 years ago
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<itemizedlist>
|
||
7 years ago
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<listitem>
|
||
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<para>Messages contained entirely within a single CRQ message</para>
|
||
|
</listitem>
|
||
5 years ago
|
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||
7 years ago
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<listitem>
|
||
|
<para>SRP requests and responses, as defined by the SRP standard</para>
|
||
|
</listitem>
|
||
5 years ago
|
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||
7 years ago
|
<listitem>
|
||
|
<para>Management Datagrams</para>
|
||
|
</listitem>
|
||
5 years ago
|
</itemizedlist>
|
||
7 years ago
|
</section>
|
||
|
<section>
|
||
|
<title>CRQ Message formats</title>
|
||
|
<para>CRQ messages are 16 bytes (128 bits) in length. Only the first byte
|
||
|
is architected by the Reliable Command/Response Transport specification
|
||
5 years ago
|
described earlier in this document. That specification is repeated in
|
||
7 years ago
|
<xref linkend="dbdoclet.50569379_71481" />.</para>
|
||
|
|
||
|
<table frame="all" pgwide="1" xml:id="dbdoclet.50569379_71481">
|
||
|
<title>First Byte of the CRQ Message</title>
|
||
|
<?dbhtml table-width="75%" ?><?dbfo table-width="75%" ?>
|
||
|
<tgroup cols="2">
|
||
|
<colspec colname="c1" colwidth="20*" align="center" />
|
||
|
<colspec colname="c2" colwidth="80*" />
|
||
|
<thead>
|
||
|
<row>
|
||
|
<entry>
|
||
|
<para><emphasis role="bold">Value</emphasis></para>
|
||
|
</entry>
|
||
|
<entry align="center">
|
||
|
<para><emphasis role="bold">Description</emphasis></para>
|
||
|
</entry>
|
||
|
</row>
|
||
|
</thead>
|
||
|
<tbody valign="middle">
|
||
|
<row>
|
||
|
<entry>
|
||
|
<para>0x00</para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para>Element is unused -- all other bytes in the element are
|
||
|
undefined</para>
|
||
|
</entry>
|
||
|
</row>
|
||
|
<row>
|
||
|
<entry>
|
||
|
<para>0x01 - 0x7F</para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para>Reserved</para>
|
||
|
</entry>
|
||
|
</row>
|
||
|
<row>
|
||
|
<entry>
|
||
|
<para>0x80</para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para>Valid Command/Response Entry -- the second byte defines the
|
||
|
entry format</para>
|
||
|
</entry>
|
||
|
</row>
|
||
|
<row>
|
||
|
<entry>
|
||
|
<para>0x81-0xFE</para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para>Reserved</para>
|
||
|
</entry>
|
||
|
</row>
|
||
|
<row>
|
||
|
<entry>
|
||
|
<para>0xFF</para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para>Valid Transport Event -- the second byte defines the
|
||
|
specific transport event</para>
|
||
|
</entry>
|
||
|
</row>
|
||
|
</tbody>
|
||
|
</tgroup>
|
||
|
</table>
|
||
|
<para>If the first byte of a CRQ message is 0x80, then it is a valid
|
||
|
Command/Response entry and the second byte describes the format of message.
|
||
|
Possible values for the second byte of the CRQ message when the first byte
|
||
5 years ago
|
is 0x80 are shown in
|
||
7 years ago
|
<xref linkend="dbdoclet.50569379_38069" />.</para>
|
||
|
|
||
|
<table frame="all" pgwide="1" xml:id="dbdoclet.50569379_38069">
|
||
|
<title>Second Byte of the CRQ Message</title>
|
||
|
<?dbhtml table-width="50%" ?><?dbfo table-width="50%" ?>
|
||
|
<tgroup cols="2">
|
||
|
<colspec colname="c1" colwidth="33*" align="center" />
|
||
|
<colspec colname="c2" colwidth="67*" />
|
||
|
<thead>
|
||
|
<row>
|
||
|
<entry>
|
||
|
<para><emphasis role="bold">Format Byte Value</emphasis></para>
|
||
|
</entry>
|
||
|
<entry align="center" >
|
||
|
<para><emphasis role="bold">Definition</emphasis></para>
|
||
|
</entry>
|
||
|
</row>
|
||
|
</thead>
|
||
|
<tbody valign="middle">
|
||
|
<row>
|
||
|
<entry>
|
||
|
<para>0x00</para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para>Unused</para>
|
||
|
</entry>
|
||
|
</row>
|
||
|
<row>
|
||
|
<entry>
|
||
|
<para>0x01</para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para>VSCSI SRP format</para>
|
||
|
</entry>
|
||
|
</row>
|
||
|
<row>
|
||
|
<entry>
|
||
|
<para>0x02</para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para>Management Datagram (MAD) format</para>
|
||
|
</entry>
|
||
|
</row>
|
||
|
<row>
|
||
|
<entry>
|
||
|
<para>0x03</para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para>i5os private format</para>
|
||
|
</entry>
|
||
|
</row>
|
||
|
<row>
|
||
|
<entry>
|
||
|
<para>0x04</para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para>AIX private format</para>
|
||
|
</entry>
|
||
|
</row>
|
||
|
<row>
|
||
|
<entry>
|
||
|
<para>0x05</para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para>Linux private format</para>
|
||
|
</entry>
|
||
|
</row>
|
||
|
<row>
|
||
|
<entry>
|
||
|
<para>0x06</para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para>Message in CRQ format</para>
|
||
|
</entry>
|
||
|
</row>
|
||
|
<row>
|
||
|
<entry>
|
||
|
<para>0x07 - 0xFF</para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para>Reserved</para>
|
||
|
</entry>
|
||
|
</row>
|
||
|
</tbody>
|
||
|
</tgroup>
|
||
|
</table>
|
||
|
<para>If the format byte is 0x01, then the rest of the message is a vscsi
|
||
|
SRP request or response message. The rest of the CRQ contents for this type
|
||
5 years ago
|
of message is shown in
|
||
7 years ago
|
<xref linkend="dbdoclet.50569379_60771" />, for messages from the clients,
|
||
5 years ago
|
and
|
||
7 years ago
|
<xref linkend="dbdoclet.50569379_58834" />, for messages from the VIOS.
|
||
|
Messages with a format byte of 0x02 are Management Datagram messages,
|
||
|
defined later in this chapter. Messages formats of 0x03, 0x04, and 0x05
|
||
|
are reserved for private, Operating System-specific messages, and are
|
||
|
currently unused by this implementation. Messages with a format byte of
|
||
|
0x06 are messages contained entirely within the CRQ.</para>
|
||
|
</section>
|
||
|
<section>
|
||
|
<title>CRQ VSCSI Client Message Format</title>
|
||
5 years ago
|
<para>Client messages are sent from the client partitions to the VIOS.
|
||
7 years ago
|
<xref linkend="dbdoclet.50569379_60771" /> shows the format of these
|
||
|
messages,</para>
|
||
|
|
||
|
<table frame="all" pgwide="1" xml:id="dbdoclet.50569379_60771">
|
||
|
<title>CRQ VSCSI Client Message</title>
|
||
|
<?dbhtml table-width="90%" ?><?dbfo table-width="90%" ?>
|
||
|
<tgroup cols="9">
|
||
|
<colspec colname="c1" colwidth="11*" align="center" />
|
||
|
<colspec colname="c2" colwidth="11*" align="center" />
|
||
|
<colspec colname="c3" colwidth="11*" align="center" />
|
||
|
<colspec colname="c4" colwidth="11*" align="center" />
|
||
|
<colspec colname="c5" colwidth="11*" align="center" />
|
||
|
<colspec colname="c6" colwidth="11*" align="center" />
|
||
|
<colspec colname="c7" colwidth="11*" align="center" />
|
||
|
<colspec colname="c8" colwidth="11*" align="center" />
|
||
|
<colspec colname="c9" colwidth="11*" align="center" />
|
||
|
<thead>
|
||
|
<row>
|
||
|
<entry>
|
||
|
<para><emphasis role="bold">Byte Offset</emphasis></para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para><emphasis role="bold">0</emphasis></para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para><emphasis role="bold">1</emphasis></para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para><emphasis role="bold">2</emphasis></para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para><emphasis role="bold">3</emphasis></para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para><emphasis role="bold">4</emphasis></para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para><emphasis role="bold">5</emphasis></para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para><emphasis role="bold">6</emphasis></para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para><emphasis role="bold">7</emphasis></para>
|
||
|
</entry>
|
||
|
</row>
|
||
|
</thead>
|
||
|
<tbody valign="middle">
|
||
|
<row>
|
||
|
<entry>
|
||
|
<para>0x00</para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para>CRQ Valid</para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para>CRQ Format</para>
|
||
|
</entry>
|
||
|
<entry nameend="c5" namest="c4">
|
||
|
<para>Reserved</para>
|
||
|
</entry>
|
||
|
<entry nameend="c7" namest="c6">
|
||
|
<para>Timeout</para>
|
||
|
</entry>
|
||
|
<entry nameend="c9" namest="c8">
|
||
|
<para>IU Length</para>
|
||
|
</entry>
|
||
|
</row>
|
||
|
<row>
|
||
|
<entry>
|
||
|
<para>0x08</para>
|
||
|
</entry>
|
||
|
<entry nameend="c9" namest="c2">
|
||
|
<para>IU Data Pointer (TCE)</para>
|
||
|
</entry>
|
||
|
</row>
|
||
|
</tbody>
|
||
|
</tgroup>
|
||
|
</table>
|
||
|
<para>For this type of message, the first byte (CRQ Valid) must be 0x80,
|
||
|
and the second byte (CRQ Format) must be 0x01. Bytes 6 and 7 of the first
|
||
|
long word are the IU Length, the length in bytes of the SRP Information
|
||
|
Unit being passed. The second long word, IU Data Pointer, is the DMA mapped
|
||
|
address of the SRP Information Unit being passed, typically an SRP Request.
|
||
|
The VIOS uses the IU length and IU Data Pointer to copy the SRP Request
|
||
|
into VIOS local memory for interpretation and processing.</para>
|
||
|
<para>Bytes 4 and 5 of the first long word, Timeout, are an optional
|
||
|
suggested timeout value for this request. If this value is greater than
|
||
|
zero, then the value may be passed along to the backing device as a
|
||
|
suggestion for how long this request is expected to take to complete. The
|
||
|
VIOS does not enforce any timeout values, but relies upon the underlaying
|
||
|
backing devices.</para>
|
||
|
<para>Management Datagram (MAD) messages also use this same format, with
|
||
|
the exception that the second byte (CRQ Format) must be set to 0x02. Bytes
|
||
|
6 and 7 of the first long word are the length of the MAD message, and the
|
||
|
second long word, IU Data Pointer, is the DMA mapped address of the MAD
|
||
|
message being passed. MAD data structures are defined later in this
|
||
|
chapter. For MAD messages, the timeout value is not used.</para>
|
||
|
</section>
|
||
|
<section>
|
||
|
<title>CRQ VSCSI VIOS Message Format</title>
|
||
|
<para>VIOS messages are sent from the VIOS to the clients, usually in
|
||
5 years ago
|
response to a request from the client. The VIOS message format is shown
|
||
7 years ago
|
<xref linkend="dbdoclet.50569379_58834" />.</para>
|
||
|
|
||
|
<table frame="all" pgwide="1" xml:id="dbdoclet.50569379_58834">
|
||
|
<title>CRQ VSCSI VIOS Message</title>
|
||
|
<?dbhtml table-width="90%" ?><?dbfo table-width="90%" ?>
|
||
|
<tgroup cols="9">
|
||
|
<colspec colname="c1" colwidth="20*" align="center" />
|
||
|
<colspec colname="c2" colwidth="10*" align="center" />
|
||
|
<colspec colname="c3" colwidth="10*" align="center" />
|
||
|
<colspec colname="c4" colwidth="10*" align="center" />
|
||
|
<colspec colname="c5" colwidth="10*" align="center" />
|
||
|
<colspec colname="c6" colwidth="10*" align="center" />
|
||
|
<colspec colname="c7" colwidth="10*" align="center" />
|
||
|
<colspec colname="c8" colwidth="10*" align="center" />
|
||
|
<colspec colname="c9" colwidth="10*" align="center" />
|
||
|
<thead>
|
||
|
<row>
|
||
|
<entry>
|
||
|
<para><emphasis role="bold">Byte Offset</emphasis></para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para><emphasis role="bold">0</emphasis></para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para><emphasis role="bold">1</emphasis></para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para><emphasis role="bold">2</emphasis></para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para><emphasis role="bold">3</emphasis></para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para><emphasis role="bold">4</emphasis></para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para><emphasis role="bold">5</emphasis></para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para><emphasis role="bold">6</emphasis></para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para><emphasis role="bold">7</emphasis></para>
|
||
|
</entry>
|
||
|
</row>
|
||
|
</thead>
|
||
|
<tbody valign="middle">
|
||
|
<row>
|
||
|
<entry>
|
||
|
<para>0x00</para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para>CRQ Valid</para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para>CRQ Format</para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para>Reserved</para>
|
||
|
</entry>
|
||
|
<entry>
|
||
|
<para>Status</para>
|
||
|
</entry>
|
||
|
<entry nameend="c7" namest="c6">
|
||
|
<para>Reserved</para>
|
||
|
</entry>
|
||
|
<entry nameend="c9" namest="c8">
|
||
|
<para>IU Length</para>
|
||
|
</entry>
|
||
|
</row>
|
||
|
<row>
|
||
|
<entry>
|
||
|
<para>0x08</para>
|
||
|
</entry>
|
||
|
<entry nameend="c9" namest="c2">
|
||
|
<para>IU TAG</para>
|
||
|
</entry>
|
||
|
</row>
|
||
|
</tbody>
|
||
|
</tgroup>
|
||
|
</table>
|
||
|
<para>For this type of message, the first byte, CRQ Valid, must be 0x80.
|
||
|
This same type of message is used for SRP Responses and for responses to
|
||
|
MAD messages. If this is an SRP Response, the second byte, CRQ Format, is
|
||
|
0x01. If this is the response to a MAD message, the second byte is 0x02.
|
||
|
Bytes 6 and 7 of the first long word, IU Length, contain the length of the
|
||
|
response. The second long word contains the tag field from the original
|
||
|
request. Both the SRP Request data structures and the MAD message data
|
||
|
structures contain a tag field for use in this message.</para>
|
||
|
<para>The Status field of the VIOS message is for reporting special,
|
||
|
non-SCSI status back to the client. This status is used for improving
|
||
|
failover times in configurations where the same storage device is visible
|
||
|
to this client over multiple adapters or when the same storage device is
|
||
|
being shared by multiple clients in clustered configurations.</para>
|
||
|
<para>If the client enables the “fast fail” feature using the
|
||
|
MAD_ENABLE_FAST_FAIL message, and if the VIOS determines that all paths to
|
||
|
a device on that client adapter have failed, the VIOS will report a status
|
||
|
of ADAPTER_FAILED (0x10) in response to a request to that device.</para>
|
||
|
<para>If the storage devices that the client are using are being shared by
|
||
|
other clients, as is the case of an IBM General Parallel File System
|
||
|
(GPFS™) configuration, and if the VIOS determines that all error
|
||
|
recovery efforts on a device have failed so that there is no point in any
|
||
|
more retries from the client, the VIOS will report a status of DEVICE_BUSY
|
||
|
(0x08) in response to a request to that device.</para>
|
||
|
<para>In both cases (ADAPTER_FAILED and DEVICE_BUSY), the client response
|
||
|
should be the same. The device is no longer accessible and the client
|
||
|
should abandon any error recovery or attempts to recover access to the
|
||
|
device using this client adapter. The client should attempt to failover to
|
||
|
another path to the device, using another adapter, if that is
|
||
|
possible.</para>
|
||
|
</section>
|
||
|
<section>
|
||
|
<title>Transport Events</title>
|
||
|
<para>If the first byte (CRQ Valid) of the CRQ message is 0xFF, then this
|
||
|
message is a Transport Event from the Hypervisor and the connection to the
|
||
|
partner has been terminated. The second byte will be the reason for the
|
||
|
Transport Event, and may be one of the following values:</para>
|
||
|
<para>0x01 - Partner Failed. The partner partition has crashed.</para>
|
||
|
<para>0x02 - Partner de-registered the CRQ. The partner partition called
|
||
|
H_FREE_CRQ for this CRQ. This may be as a result of error recovery, as in
|
||
|
the case of a protocol error, or it may be the result of the system
|
||
|
administrator removing a client or VIOS adapter.</para>
|
||
|
<para>0x06 - Client has been migrated as the result of a Partition Mobility
|
||
|
operation. Only clients can be migrated and only clients that send the
|
||
|
MAD_CAPABILITIES message are considered to be candidates for
|
||
|
migration.</para>
|
||
|
</section>
|
||
|
<section>
|
||
|
<title>Messages in CRQs</title>
|
||
|
<para>If the first byte (CRQ Valid) of the CRQ message is 0x80, and the
|
||
|
second byte (CRQ Format) is 0x06, then this is a message contained entirely
|
||
|
within the CRQ. The rest of the message, including the IU Data Pointer, is
|
||
|
unused and must be initialized to zero. These messages do not require any
|
||
|
resources on the client or VIOS, and are not subject to flow control, so
|
||
|
may be sent at any time. However, they should be used sparingly, because
|
||
|
they do take up an entry in the CRQ and they do require interrupt
|
||
|
processing time to respond to them, The third byte defines the
|
||
|
message.</para>
|
||
|
<para>Only two messages of this type have been defined to this
|
||
|
point:</para>
|
||
|
<para>0xF5 - PING</para>
|
||
|
<para>0xF6 - PING RESPONSE</para>
|
||
|
<para>If the VIOS is not able to process interrupts, the client will likely
|
||
|
be hung, waiting on a completion from the VIOS. To detect this condition,
|
||
|
the client may send a PING to the VIOS. If the VIOS is capable of
|
||
|
processing an interrupt, it responds to the PING with a PING RESPONSE,
|
||
|
directly at interrupt level. If the client does not receive the PING
|
||
|
RESPONSE within a reasonably short period of time, it may choose to declare
|
||
|
the VIOS dead and attempt to failover to another client adapter. Likewise,
|
||
|
if the VIOS for some reason needs to determine if the client is still
|
||
|
alive, it may send a PING to the client. The client should respond as
|
||
|
expeditiously as possible, with a PING RESPONSE.</para>
|
||
|
</section>
|
||
|
<section>
|
||
|
<title>VSCSI Management Datagrams (MADs)</title>
|
||
|
<para>VSCSI uses a number of messages that are not defined by the SRP
|
||
|
standard. The paradigm used for these messages is the Management Datagram,
|
||
|
discussed in the SRP and Fibre Channel specifications. Like all SRP
|
||
|
messages, the MADs are initiated by the client partition and the VIOS
|
||
|
responds to them. To initiate a MAD, the client sets the valid field to
|
||
|
0x80, sets the format field to 0x02 (MAD_FORMAT), sets the length field to
|
||
|
the length of the data structure describing the MAD, sets the ioba field to
|
||
|
the mapped memory address of the data structure describing the MAD, and
|
||
|
uses the H_SEND_CRQ service provided by the Hypervisor to send the request
|
||
|
to the VIOS.</para>
|
||
|
<para>Most of these MADs can be initiated any time after the initialization
|
||
|
messages (INIT, INIT_COMPLETE) have been exchanged. Some of them are most
|
||
|
appropriately done before the SRP_login message and the start of normal
|
||
|
data transfer operations. These are: MAD_EMPTY_IU;
|
||
|
MAD_ADAPTER_INFO_REQUEST; MAD_CAPABILITIES_EXCHANGE; and
|
||
|
MAD_ENABLE_FAST_FAIL. Note that before the SRP_login message, resources
|
||
|
allocated by the VIOS for a client are limited so a client should wait for
|
||
|
one MAD to complete before issuing another, with the single exception of
|
||
|
the MAD_EMPTY_IU message. None of them are required for normal data
|
||
|
transfer operations between the client and VIOS. However, the
|
||
|
MAD_ADAPTER_INFO_REQUEST provides information that customers find highly
|
||
|
desirable, so using it is strongly recommended. In addition, the
|
||
|
MAD_ADAPTER_INFO_REQUEST returns the size of the largest data transfer
|
||
|
operation that the VIOS will accept from this client. Failure to honor this
|
||
|
limit can result in client failure. And the MAD_CAPABILITIES_EXCHANGE
|
||
|
message is required before a client is allowed to participate in partition
|
||
|
mobility operation.</para>
|
||
|
<para>The inter_op structure is used to specify the type of MAD being
|
||
|
sent.</para>
|
||
|
|
||
5 years ago
|
<programlisting><![CDATA[typedef struct _inter_op_fields{
|
||
7 years ago
|
uint32_t type;
|
||
|
uint16_t status;
|
||
|
uint16_t length;
|
||
|
uint64_t tag;
|
||
|
}inter_op;]]></programlisting>
|
||
|
|
||
|
<para>The type field describes the MAD and will be discussed in the
|
||
|
paragraphs that follow.</para>
|
||
|
<para>The status field describes the result of the MAD operation. The
|
||
|
client is required to initialize the status field to zero. The VIOS
|
||
|
responds one of three ways:</para>
|
||
|
|
||
|
<programlisting><![CDATA[#define MAD_SUCCESS 0x0
|
||
|
#define MAD_NOT_SUPPORTED 0xF1
|
||
|
#define MAD_FAILED 0xF7]]></programlisting>
|
||
5 years ago
|
|
||
7 years ago
|
<para>MAD_NOT_SUPPORTED is returned if the VIOS is down-level. MAD_FAILED
|
||
|
is returned in every other situation where the MAD did not succeed.</para>
|
||
|
<para>The length field is set to the length of the data structure(s) used
|
||
|
in the command.</para>
|
||
|
<para>The tag field is reflected back to the client in the response to the
|
||
|
MAD. The VIOS uses H_SEND_CRQ to send a response with the format set to
|
||
|
0x02 (MAD_FORMAT) and the ioba field is set to the tag field specified by
|
||
|
the client.</para>
|
||
|
<para>The type field may be set to one of the following:</para>
|
||
|
|
||
|
<programlisting><![CDATA[
|
||
|
#define MAD_EMPTY_IU 0x01
|
||
|
#define MAD_ERROR_LOGGING_REQUEST 0x02
|
||
|
#define MAD_ADAPTER_INFO_REQUEST 0x03
|
||
|
#define RESERVED 0x04
|
||
|
#define MAD_CAPABILITIES_EXCHANGE 0x05
|
||
|
#define MAD_PHYS_ADAP_INFO_REQUEST 0x06
|
||
|
#define MAD_TAPE_PASSTHROUGH_REQUEST 0x07
|
||
|
#define MAD_ENABLE_FAST_FAIL 0x08]]></programlisting>
|
||
|
|
||
|
|
||
|
<section>
|
||
|
<title>#define MAD_EMPTY_IU 0x01</title>
|
||
|
<para>The client sends a MAD_EMPTY_IU command if it wishes to receive an
|
||
|
SRP target_logout before the VIOS closes the CRQ. The target_logout SRP
|
||
|
response contains the reason that the VIOS is closing the CRQ.</para>
|
||
|
<para>The MAD_EMPTY_IU command uses the following data structure:</para>
|
||
|
|
||
|
<programlisting><![CDATA[struct mad_empty_iu {
|
||
|
inter_op op;
|
||
|
uint64_t desp;
|
||
|
uint port;
|
||
|
};]]></programlisting>
|
||
|
|
||
|
<para>The inter_op structure is initialized with the type field set to
|
||
|
0x01 (MAD_EMPTY_IU), the status field set to zero, the length field set
|
||
|
to the size of the mad_empty_iu structure, and the tag field set as
|
||
|
described above.</para>
|
||
|
<para>The desp field is set to mapped memory address of the SRP_T_LOGOUT
|
||
|
response data structure. The client must not unmap, free, or re-use this
|
||
|
memory until it receives the SRP target_logout or the CRQ is
|
||
|
closed.</para>
|
||
|
<para>The port field is unused at this time.</para>
|
||
|
</section>
|
||
|
<section>
|
||
|
<title>#define MAD_ERROR_LOGGING_REQUEST 0x02</title>
|
||
|
<para>The client sends the MAD_ERROR_LOGGING_REQUEST when it wishes the
|
||
|
VIOS to write an entry in the system error log on its behalf. Hardware
|
||
|
errors in physical storage components on the VIOS usually result in
|
||
|
errors on the client partition using that physical storage. The
|
||
|
MAD_ERROR_LOGGING REQUEST places client errors in the system error log in
|
||
|
proximity to the original hardware error to enable service personnel to
|
||
|
assess the impact of the original hardware error.</para>
|
||
|
<para>The MAD_ERROR_LOGGING_REQUEST uses the following data
|
||
|
structure:</para>
|
||
|
|
||
5 years ago
|
<programlisting><![CDATA[struct mad_error_logging_request{
|
||
7 years ago
|
inter_op op;
|
||
|
uint64_t buffer;
|
||
|
};]]></programlisting>
|
||
|
|
||
|
<para>The inter_op structure is initialized with the type field set to
|
||
|
0x02 (MAD_ERROR_LOGGING_REQUEST), the status field set to zero, the
|
||
|
length field set to the size of the mad_error_log structure plus the size
|
||
|
of the buffer of additional data, if any, and the tag field set as
|
||
|
described above.</para>
|
||
|
<para>The buffer field points to a mad_error_log structure.</para>
|
||
|
|
||
|
<programlisting><![CDATA[struct mad_error_log{
|
||
|
uint64_t lun; // logical unit address
|
||
|
uint64_t correlator; // logged on both client and server in order to be
|
||
|
// able to associate an entry on the client with
|
||
|
// one on the server
|
||
|
uint64_t reserved; // future expansion
|
||
|
uint32_t error_id; // client partition specific (-1 if none is available)
|
||
|
int32_t buffer_size;
|
||
|
// size of character buffer to log
|
||
|
char client_name[32]; // for example “vscsi0”
|
||
|
char device_name[32]; // for example “hdisk0”
|
||
|
int32_t partition; // partition number
|
||
|
#define LOG_DATA_BINARY 1
|
||
|
#define LOG_DATA_ASCII 2
|
||
|
int32_t flags; // type of data in buffer
|
||
|
char buffer[1]; // start of the buffer, buffer_size bytes
|
||
|
};]]></programlisting>
|
||
|
|
||
|
<para>The lun field is set to the Logical Unit Number (LUN) of the device
|
||
|
on the client that is logging the error.</para>
|
||
|
<para>The correlator field is optional. If used, it should have a unique
|
||
|
value that can be used to correlate the error message on the client with
|
||
|
the error message on the VIOS.</para>
|
||
|
<para>The error_id field is set to a client-specific number associated
|
||
|
with the error.</para>
|
||
|
<para>The buffer_size is set to the length of the buffer of additional
|
||
|
data, which is optional.</para>
|
||
|
<para>The client_name array is set to the name by which this client
|
||
|
adapter instance is known on the client partition, for example
|
||
|
“vscsi0”.</para>
|
||
|
<para>The device_name array is set to the name by which the device
|
||
|
logging the error is known on the client partition, for example
|
||
|
“hdisk0”.</para>
|
||
|
<para>The partition field is set to the number of the client partition
|
||
|
requesting that the error be logged.</para>
|
||
|
<para>The flags field specifies the type of data contained in the
|
||
|
optional buffer.</para>
|
||
|
<para>The buffer, if used, starts immediately after the mad_error_log
|
||
|
structure. The buffer is not logged by the VIOS at this time.</para>
|
||
|
</section>
|
||
|
<section>
|
||
|
<title>#define MAD_ADAPTER_INFO_REQUEST 0x03</title>
|
||
|
<para>The client sends the MAD_ADAPTER_INFO_REQUEST to the VIOS to inform
|
||
|
the VIOS of the client’s identity. The VIOS responds with the
|
||
|
equivalent information about itself. The VIOS uses the client information
|
||
|
provided in the MAD_ADAPTER_INFO_REQUEST for the display in the
|
||
|
“lsmap” command. Use of this MAD is not enforced by VIOS.
|
||
|
However, customers have found the information useful enough to insist
|
||
|
that it be used. The MAD_ADAPTER_INFO_REQUEST may also be used after a
|
||
|
Partition Mobility operation to allow the client to update the
|
||
|
information on the VIOS, which may have changed during the
|
||
|
migration.</para>
|
||
|
<para>The MAD_ADAPTER_INFO_REQUEST uses the following data
|
||
|
structure:</para>
|
||
|
|
||
5 years ago
|
<programlisting><![CDATA[struct mad_adapter_information_request{
|
||
7 years ago
|
inter_op op;
|
||
|
uint64_t buffer;
|
||
|
};]]></programlisting>
|
||
|
|
||
|
<para>The inter_op structure is initialized with the type field set to
|
||
|
0x03 (MAD_ADAPTER_INFO_REQUEST), the status field set to zero, the length
|
||
|
field set to the size of the mad_adapter_information_payload structure,
|
||
|
and the tag field set as described above. The buffer field points to
|
||
|
mapped memory address of a mad_adapter_information_payload
|
||
|
structure.</para>
|
||
|
|
||
|
<programlisting><![CDATA[typedef struct mad_adapter_information_payload{
|
||
|
char srp_version[8]; // initially 16.a
|
||
|
char partition_name[96]; // root node property ibm,partition-name
|
||
|
uint32_t partition_number; // root node property ibm,partition-no
|
||
|
#define MAD_VERSION_1 1
|
||
|
uint32_t mad_version; // initially 1
|
||
|
#define OS400 0x01
|
||
|
#define LINUX 0x02
|
||
|
#define AIX 0x03
|
||
|
#define OFW 0x04
|
||
|
uint32_t os_type;
|
||
|
uint32_t port_max_txu[8];
|
||
|
}partner_info;]]></programlisting>
|
||
|
|
||
|
<para>The srp_version field is a NULL-terminated character array with the
|
||
|
version number of the SRP standard to which the partition complies.
|
||
|
Current versions of the VIOS and clients all support SRP revision 16.a.
|
||
|
The VIOS does not validate or enforce this field currently.</para>
|
||
|
<para>The partition name is the ASCII string representing the name of the
|
||
|
partition from the root node in the Open Firmware device tree.</para>
|
||
|
<para>The partition number is the integer number identifying the
|
||
|
partition from the root node in the Open Firmware device tree. Note that
|
||
|
partition number 0 is reserved for the hypervisor.</para>
|
||
|
<para>The mad_version field is set to the version of MAD messages
|
||
|
supported by the partition. The MAD messages described in this document
|
||
|
is version 1. The VIOS does not currently validate or enforce this
|
||
|
version.</para>
|
||
|
<para>The os_type field is set to the type of Operating System being run
|
||
|
on the partition. The VIOS uses this information to allocate additional
|
||
|
resources for client partitions that have unique requirements and to
|
||
|
return different values for sense data in error situations. The VIOS has
|
||
|
been able to make minor behavior changes to the device on behalf of
|
||
|
clients that use this field.</para>
|
||
|
<para>The port_max_txu array is used by the VIOS to report the size of
|
||
|
the largest single request that it can handle. Currently only the first
|
||
|
entry (port_max_txu[0]) is used. The client initializes this field to
|
||
|
zero. The VIOS responds with at least a value of 0x40000, meaning that it
|
||
|
is prepared to deal with a request to transfer at least 256,000 bytes of
|
||
|
data. The VIOS can respond with a larger value, depending on the
|
||
|
resources available and the capabilities of the physical device providing
|
||
|
storage.</para>
|
||
|
<para>
|
||
|
<emphasis role="bold">NOTE</emphasis>: If the VIOS reports a maximum transfer value
|
||
|
larger than the minimum of 0x40000, and subsequently a device which
|
||
|
cannot support that larger maximum transfer value is added to the device
|
||
|
inventory of this host adapter, the VIOS will log an informative error
|
||
|
and not report that new device in a REPORT_LUNS request until the client
|
||
|
has issued another MAD adapter information request. This prevents the
|
||
|
client from passing a data transfer request to a device which is too
|
||
|
large for that device to handle. The VIOS will return such requests with
|
||
|
an error. Optical devices typically have minimal maximum transfer
|
||
|
values.</para>
|
||
|
</section>
|
||
|
<section>
|
||
|
<title>#define MAD_CAPABILITIES_EXCHANGE 0x05</title>
|
||
|
<para>The MAD_CAPABILITIES_EXCHANGE command is used to allow the client
|
||
|
and VIOS to negotiate support for capabilities that may be required with
|
||
|
a partition migration. The data structures used are the capabilities
|
||
|
structure, followed by at least one specific capability structure. The
|
||
|
client uses a bit-mask to advertise the capabilities that it can support
|
||
|
by setting the bits representing those capabilities to one. The VIOS
|
||
|
responds by turning off (setting to zero) the bits for any capabilities
|
||
|
that it cannot support. This allows clients and VIOSs at a variety of
|
||
|
levels to cooperate in the partition migration operation. The client is
|
||
|
required to support a minimum level of capabilities in order to be
|
||
|
considered to be a candidate for migration.</para>
|
||
|
<para>The MAD_CAPABILITIES_EXCHANGE command uses the following data
|
||
|
structure:</para>
|
||
|
|
||
|
<programlisting><![CDATA[struct capabilities_mad{
|
||
|
inter_op op;
|
||
|
uint64_t buffer;
|
||
|
};]]></programlisting>
|
||
|
|
||
|
<para>The inter_op field is initialized with the type field set to 0x05
|
||
|
(MAD_CAPABILITIES_EXCHANGE), the status field initialized to zero, the
|
||
|
length field set to the size of the capabilities structures being passed,
|
||
|
and the tag field set as described above. The capabilities structures
|
||
|
must include at least the capabilities structure and the mig_cap
|
||
|
structure.</para>
|
||
|
<para>The buffer field contains the mapped memory address of a buffer
|
||
|
containing these structures.</para>
|
||
|
|
||
|
<programlisting><![CDATA[struct capabilities{
|
||
|
// Allows the server to put a LUN in the proper state
|
||
|
// after migration. The flags are needed if one or
|
||
|
// LUN are using client reserve
|
||
|
#define CLIENT_MIGRATED 0x01
|
||
|
#define CLIENT_RECONNECT 0x02
|
||
|
// The the client should always set this flag field, it will
|
||
|
// will be reset if the server found some capabilities in the
|
||
|
// list it is not capable of supporting. If the server resets this
|
||
|
// flag field there is at least one capability in the list it does
|
||
|
// support
|
||
|
#define CAP_LIST_SUPPORTED 0x04
|
||
|
// The server sets this flag it overwrites some filed in
|
||
|
// the capabilities list. It is not set for overwriting
|
||
|
// the name or location field
|
||
|
#define CAP_LIST_DATA 0x08
|
||
|
unsigned int flags;
|
||
|
// Either a Null string or NULL terminated ASCII strings.
|
||
|
// If string is not NULL it may be displayed by the server
|
||
|
// for the system administrator.
|
||
|
char name[32];
|
||
|
char loc[32];
|
||
|
// list of capabilities follow
|
||
|
};]]></programlisting>
|
||
|
|
||
|
<para>The flags field is always set to at least CAP_LIST_SUPPORTED by the
|
||
|
client. If the client is sending this command as the result of a
|
||
|
successful partition migration operation, it should also set the
|
||
|
CLIENT_MIGRATED flag. If the client is sending this command as the result
|
||
|
of a VIOS reboot or the VIOS has reset the CRQ, it should also set the
|
||
|
CLIENT_RECONNECT flag. If the VIOS cannot support all of the capabilities
|
||
|
in the list passed by the client, it will turn off the CAP_LIST_SUPPORTED
|
||
|
flag. If the VIOS overwrites some of the data in the capabilities list,
|
||
|
it will set the CAP_LIST_DATA flag.</para>
|
||
|
<para>The name array is filled with the NULL-terminated string
|
||
|
representing the name by which this client adapter instance is known on
|
||
|
the client partition, for example “vscsi0”.</para>
|
||
|
<para>The loc array is filled with the NULL-terminated string from the
|
||
|
“loc-code” field of the adapter node in the Open Firmware
|
||
|
device tree for this client adapter, for example
|
||
|
“U9117.MMA.107086C-V6-C5-T1”.</para>
|
||
|
<para>Following the capabilities structure is a list of capabilities to
|
||
|
be negotiated. Capabilities currently supported by the VIOS are
|
||
|
MIGRATION_CAPABILITIES and RESERVATION_CAPABILITIES.</para>
|
||
|
|
||
|
<programlisting><![CDATA[struct capability_common{
|
||
|
// Which capability
|
||
|
#define MIGRATION_CAPABILITIES 0x01
|
||
|
#define RESERVATION_CAPABILITIES 0x02
|
||
|
unsigned int cap_type;
|
||
|
// Length of this capability
|
||
|
// including the size of this structure
|
||
|
// in bytes
|
||
|
int16_t length;
|
||
|
// Client initializes to 0x01, server zeros
|
||
|
// if this particular capability is not supported
|
||
|
#define SERVER_DOES_NOT_SUPPORTS_CAP 0x0
|
||
|
#define SERVER_SUPPORTS_CAP 0x01
|
||
|
#define SERVER_CAP_DATA 0x02
|
||
|
uint16_t server_support;
|
||
|
};]]></programlisting>
|
||
|
|
||
|
<para>The capability_common structure is included in each capability
|
||
|
structure and describes the type of capability being negotiated.</para>
|
||
|
<para>The cap_type field is set to the type of capability.
|
||
|
MIGRATION_CAPABILITIES and RESERVATION_CAPABILITIES are the only types of
|
||
|
capabilities currently supported.</para>
|
||
|
<para>The length field is set to the size of the capabilities structure,
|
||
|
currently either mig_cap or reserve_cap.</para>
|
||
|
<para>The server_support field is initialized by the client to 1. If the
|
||
|
VIOS does not support that capability, it clears the field.</para>
|
||
|
<para>The capabilities structure used for negotiating migration
|
||
|
capabilities is as follows:</para>
|
||
|
|
||
|
<programlisting><![CDATA[struct mig_cap{
|
||
|
struct capability_common common;
|
||
|
unsigned int ecl;
|
||
|
};]]></programlisting>
|
||
|
|
||
|
<para>The ecl field contains the effective capability level. The client
|
||
|
sets it to the current migration capability level that this client is
|
||
|
capable of supporting. If this level is lower than the level that the
|
||
|
VIOS can support or higher than the VIOS currently supports, the VIOS
|
||
|
sets the server_support to SERVER_CAP_DATA, sets the ecl field to the
|
||
|
lowest level it can support or the level currently supported, as
|
||
|
appropriate, and sets flags field of the capabilities structure to
|
||
|
CAP_LIST_DATA, to inform the client of the difference in the levels of
|
||
|
migration capabilities supported. Currently, the only migration
|
||
|
capability level supported is 1.</para>
|
||
|
<para>The structure used in negotiating reservation capabilities is as
|
||
|
follows:</para>
|
||
|
|
||
|
<programlisting><![CDATA[struct reserve_cap{
|
||
|
struct capability_common common;
|
||
|
// Allow for future expansion of different
|
||
|
// types of reserves.
|
||
|
#define CLIENT_RESERVE_SCSI_2 0x01
|
||
|
unsigned int type;
|
||
|
};]]></programlisting>
|
||
|
|
||
|
<para>If the client is capable of breaking and re-establishing SCSI-2
|
||
|
reservations after a migration event, it should set the type field to
|
||
|
CLIENT_RESERVE_SCSI_2. Otherwise, it should initialize the type field to
|
||
|
zero.</para>
|
||
|
</section>
|
||
|
<section>
|
||
|
<title>#define MAD_PHYS_ADAP_INFO_REQUEST 0x06</title>
|
||
|
<para>The MAD_PHYS_ADAP_INFO_REQUEST returns data about the physical
|
||
|
adapter to which the target device is attached, if the device supports
|
||
|
it. The only device currently supporting this request is virtual tape.
|
||
|
The data structure used with the MAD_PHYS_ADAP_INFO_REQUEST is as
|
||
|
follows:</para>
|
||
|
|
||
|
<programlisting><![CDATA[struct mad_phys_adapter_info_request{
|
||
|
inter_op op;
|
||
|
uint64_t buffer;
|
||
|
};]]></programlisting>
|
||
|
|
||
|
<para>The client initializes the inter_op field, with the type set to
|
||
|
0x06 (MAD_PHYS_ADAP_INFO_REQUEST), the status field initialized to zero,
|
||
|
the length field set to the size of the mad_phys_adapter_info structure,
|
||
|
the tag field set as described above, and the buffer field set to the
|
||
|
mapped memory address of a mad_phys_adapter_info structure.</para>
|
||
|
|
||
|
<programlisting><![CDATA[struct mad_phys_adapter_info{
|
||
|
uint64_t lun;
|
||
|
#define MAD_PHYS_ADAP_INFO_VERSION 0x00000001
|
||
|
uint32_t version;
|
||
|
#ifndef MAX_FRUPN_SIZE
|
||
|
#define MAX_FRUPN_SIZE 128
|
||
|
#endif
|
||
|
#ifndef MAX_FRUSN_SIZE
|
||
|
#define MAX_FRUSN_SIZE 128
|
||
|
#endif
|
||
|
#ifndef MAX_PHYSLOC_SIZE
|
||
|
#define MAX_PHYSLOC_SIZE 256
|
||
|
#endif
|
||
|
char fruPartNumber [MAX_FRUPN_SIZE];
|
||
|
char fruSerialNumber [MAX_FRUSN_SIZE];
|
||
|
char physLocationCode [MAX_PHYSLOC_SIZE];
|
||
|
char reserved [4];
|
||
|
};]]></programlisting>
|
||
|
|
||
|
<para>The client sets the lun field to the Logical Unit Number (LUN) of
|
||
|
the virtual device for which it is requesting the physical adapter
|
||
|
information, and it sets the version to 0x01
|
||
|
(MAD_PHYS_ADAP_INFO_VERSION).</para>
|
||
|
<para>If the target device supports returning the physical adapter
|
||
|
information, the VIOS copies the Field Replaceable Unit (FRU) part
|
||
|
number, the FRU serial number, and the physical location code into the
|
||
|
appropriate arrays and returns that information to the client. This
|
||
|
information is intended for use by customer service engineers, to assist
|
||
|
them in repairing physical tape devices.</para>
|
||
|
</section>
|
||
|
<section>
|
||
|
<title>#define MAD_TAPE_PASSTHROUGH_REQUEST 0x07</title>
|
||
|
<para>The MAD_TAPE_PASSTHROUGH_REQUEST enables or disables SCSI command
|
||
|
data blocks (CDBs) to be passed directly to the physical tape device
|
||
|
driver without examination or emulation by the VIOS drivers.</para>
|
||
|
<para>The structure used with the MAD_TAPE_PASSTHROUGH_REQUEST is as
|
||
|
follows:</para>
|
||
|
|
||
|
<programlisting><![CDATA[struct mad_tape_passthrough{
|
||
|
inter_op op;
|
||
|
uint64_t lun;
|
||
|
#define MAD_TAPE_PASSTHRU_VERSION 0x00000001
|
||
|
uint32_t version;
|
||
|
/*********************************************
|
||
|
* The below defines are used to enable or
|
||
|
* disable the passthrough mode for virtual
|
||
|
* tape devices supported by the server
|
||
|
*********************************************/
|
||
|
#define TAPE_PASSTHROUGH_ENABLE 0x00000001
|
||
|
#define TAPE_PASSTHROUGH_DISABLE 0x00000002
|
||
|
uint32_t passThru;
|
||
|
};]]></programlisting>
|
||
|
|
||
|
<para>The client initializes the inter_op structure by setting the type
|
||
|
field to 0x07 (MAD_TAPE_PASSTHROUGH_REQUEST), setting the status field to
|
||
|
zero, setting the length field to the size of the mad_tape_passthrough
|
||
|
structure, and setting the tag field as described above. The lun field is
|
||
|
set to the Logical Unit Number of a virtual tape device on this client
|
||
|
adapter. The version is set to 0x00000001 (MAD_TAPE_PASSTHRU_VERSION).
|
||
|
The passThru is set to either 0x00000001 (TAPE_PASSTHROUGH_ENABLE) or
|
||
|
0x00000002 (TAPE_PASSTHROUGH_DISABLE).</para>
|
||
|
<para>When tape passthrough is enabled, the SCSI Command Data Blocks are
|
||
|
sent directly to the tape head driver, without examination or emulation
|
||
|
by the VIOS drivers.</para>
|
||
|
</section>
|
||
|
<section>
|
||
|
<title>#define MAD_ENABLE_FAST_FAIL 0x08</title>
|
||
|
<para>The MAD_ENABLE_FAST_FAIL command enables the VIOS to provide a hint
|
||
|
to the client that a physical device is no longer accessible so that a
|
||
|
failover to alternate paths, if any, should be attempted.</para>
|
||
|
<para>The only structure used with the MAD_ENABLE_FAST_FAIL command is
|
||
|
the inter_op structure. The type field is set to 0x08
|
||
|
(MAD_ENABLE_FAST_FAIL), the status field is initialized to zero, the
|
||
|
length field is set to the size of the inter_op structure, and the tag
|
||
|
field is set as described above.</para>
|
||
|
<para>When the MAD_ENABLE_FAST_FAIL has completed successfully and the
|
||
|
VIOS determines that a device is no longer responding, when the VIOS is
|
||
|
completing an I/O request for that device back to the client, the VIOS
|
||
|
will set the status field in the CRQ message to 0x10 (ADAPTER_FAILED), in
|
||
|
addition to returning the normal device error and sense data. Fast fail
|
||
|
is disabled by closing the CRQ.</para>
|
||
|
<para>Two additional messages may be exchanged between clients and a VIOS
|
||
|
- PING and PING_RESPONSE. If a partition needs to know if the other
|
||
|
partition is still functional and at least able to respond to an
|
||
|
interrupt, it can send a PING message to the other partition. The other
|
||
|
partition should respond with a PING_RESPONSE. These are very lightweight
|
||
|
messages that require no resources. They fit entirely within the first
|
||
|
64-bit quantity of the CRQ message. The PING_RESPONSE should be sent from
|
||
|
the interrupt code, immediately after receiving the PING.</para>
|
||
|
<para>To send a PING, the valid bit is set to one, the CRQ format field
|
||
|
is set to 0x06 (MESSAGE_IN_CRQ), and the status field is set to 0xF5
|
||
|
(PING).</para>
|
||
|
<para>To send a PING_RESPONSE, the valid bit is set to one, the CRQ
|
||
|
format field is set to 0x06 (MESSAGE_IN_CRQ), and the status field is set
|
||
|
to 0xF6 (PING_RESPONSE).</para>
|
||
|
<para>It is strongly recommended that PING messages be used very
|
||
|
sparingly. One way to fill a CRQ with ping messages is to halt the VIOS
|
||
|
in kdb while the AIX client has requests active on it.</para>
|
||
|
|
||
|
</section>
|
||
|
</section>
|
||
5 years ago
|
</appendix>
|