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A tiny Open POWER ISA softcore written in VHDL 2008
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microwatt/mmu.vhdl

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library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
library work;
use work.common.all;
-- Radix MMU
-- Supports 4-level trees as in arch 3.0B, but not the two-step translation for
-- guests under a hypervisor (i.e. there is no gRA -> hRA translation).
entity mmu is
port (
clk : in std_ulogic;
rst : in std_ulogic;
l_in : in Loadstore1ToMmuType;
l_out : out MmuToLoadstore1Type;
d_out : out MmuToDcacheType;
d_in : in DcacheToMmuType;
i_out : out MmuToIcacheType
);
end mmu;
architecture behave of mmu is
type state_t is (IDLE,
DO_TLBIE,
TLB_WAIT,
PART_TBL_READ,
PART_TBL_WAIT,
PART_TBL_DONE,
PROC_TBL_READ,
PROC_TBL_WAIT,
SEGMENT_CHECK,
RADIX_LOOKUP,
RADIX_READ_WAIT,
RADIX_LOAD_TLB,
RADIX_FINISH
);
type reg_stage_t is record
-- latched request from loadstore1
valid : std_ulogic;
iside : std_ulogic;
store : std_ulogic;
priv : std_ulogic;
addr : std_ulogic_vector(63 downto 0);
inval_all : std_ulogic;
-- config SPRs
ptcr : std_ulogic_vector(63 downto 0);
pid : std_ulogic_vector(31 downto 0);
-- internal state
state : state_t;
done : std_ulogic;
err : std_ulogic;
prtbl : std_ulogic_vector(63 downto 0);
ptb_valid : std_ulogic;
pgtbl0 : std_ulogic_vector(63 downto 0);
pt0_valid : std_ulogic;
pgtbl3 : std_ulogic_vector(63 downto 0);
pt3_valid : std_ulogic;
shift : unsigned(5 downto 0);
mask_size : unsigned(4 downto 0);
pgbase : std_ulogic_vector(55 downto 0);
pde : std_ulogic_vector(63 downto 0);
invalid : std_ulogic;
badtree : std_ulogic;
segerror : std_ulogic;
perm_err : std_ulogic;
rc_error : std_ulogic;
end record;
signal r, rin : reg_stage_t;
signal addrsh : std_ulogic_vector(15 downto 0);
signal mask : std_ulogic_vector(15 downto 0);
signal finalmask : std_ulogic_vector(43 downto 0);
begin
-- Multiplex internal SPR values back to loadstore1, selected
-- by l_in.sprnf.
l_out.sprval <= r.ptcr when l_in.sprnf = '1' else x"00000000" & r.pid;
mmu_0: process(clk)
begin
if rising_edge(clk) then
if rst = '1' then
r.state <= IDLE;
r.valid <= '0';
r.ptb_valid <= '0';
r.pt0_valid <= '0';
r.pt3_valid <= '0';
r.ptcr <= (others => '0');
r.pid <= (others => '0');
else
if rin.valid = '1' then
report "MMU got tlb miss for " & to_hstring(rin.addr);
end if;
if l_out.done = '1' then
report "MMU completing op without error";
end if;
if l_out.err = '1' then
report "MMU completing op with err invalid=" & std_ulogic'image(l_out.invalid) &
" badtree=" & std_ulogic'image(l_out.badtree);
end if;
if rin.state = RADIX_LOOKUP then
report "radix lookup shift=" & integer'image(to_integer(rin.shift)) &
" msize=" & integer'image(to_integer(rin.mask_size));
end if;
if r.state = RADIX_LOOKUP then
report "send load addr=" & to_hstring(d_out.addr) &
" addrsh=" & to_hstring(addrsh) & " mask=" & to_hstring(mask);
end if;
r <= rin;
end if;
end if;
end process;
-- Shift address bits 61--12 right by 0--47 bits and
-- supply the least significant 16 bits of the result.
addrshifter: process(all)
variable sh1 : std_ulogic_vector(30 downto 0);
variable sh2 : std_ulogic_vector(18 downto 0);
variable result : std_ulogic_vector(15 downto 0);
begin
case r.shift(5 downto 4) is
when "00" =>
sh1 := r.addr(42 downto 12);
when "01" =>
sh1 := r.addr(58 downto 28);
when others =>
sh1 := "0000000000000" & r.addr(61 downto 44);
end case;
case r.shift(3 downto 2) is
when "00" =>
sh2 := sh1(18 downto 0);
when "01" =>
sh2 := sh1(22 downto 4);
when "10" =>
sh2 := sh1(26 downto 8);
when others =>
sh2 := sh1(30 downto 12);
end case;
case r.shift(1 downto 0) is
when "00" =>
result := sh2(15 downto 0);
when "01" =>
result := sh2(16 downto 1);
when "10" =>
result := sh2(17 downto 2);
when others =>
result := sh2(18 downto 3);
end case;
addrsh <= result;
end process;
-- generate mask for extracting address fields for PTE address generation
addrmaskgen: process(all)
variable m : std_ulogic_vector(15 downto 0);
begin
-- mask_count has to be >= 5
m := x"001f";
if is_X(r.mask_size) then
m := (others => 'X');
else
for i in 5 to 15 loop
if i < to_integer(r.mask_size) then
m(i) := '1';
end if;
end loop;
end if;
mask <= m;
end process;
-- generate mask for extracting address bits to go in TLB entry
-- in order to support pages > 4kB
finalmaskgen: process(all)
variable m : std_ulogic_vector(43 downto 0);
begin
m := (others => '0');
for i in 0 to 43 loop
if is_X(r.shift) then
m(i) := 'X';
elsif i < to_integer(r.shift) then
m(i) := '1';
end if;
end loop;
finalmask <= m;
end process;
mmu_1: process(all)
variable v : reg_stage_t;
variable dcreq : std_ulogic;
variable tlb_load : std_ulogic;
variable itlb_load : std_ulogic;
variable tlbie_req : std_ulogic;
variable ptbl_rd : std_ulogic;
variable prtbl_rd : std_ulogic;
variable pt_valid : std_ulogic;
variable effpid : std_ulogic_vector(31 downto 0);
variable prtable_addr : std_ulogic_vector(63 downto 0);
variable rts : unsigned(5 downto 0);
variable mbits : unsigned(5 downto 0);
variable pgtable_addr : std_ulogic_vector(63 downto 0);
variable pte : std_ulogic_vector(63 downto 0);
variable tlb_data : std_ulogic_vector(63 downto 0);
variable nonzero : std_ulogic;
variable pgtbl : std_ulogic_vector(63 downto 0);
variable perm_ok : std_ulogic;
variable rc_ok : std_ulogic;
variable addr : std_ulogic_vector(63 downto 0);
variable data : std_ulogic_vector(63 downto 0);
begin
v := r;
v.valid := '0';
dcreq := '0';
v.done := '0';
v.err := '0';
v.invalid := '0';
v.badtree := '0';
v.segerror := '0';
v.perm_err := '0';
v.rc_error := '0';
tlb_load := '0';
itlb_load := '0';
tlbie_req := '0';
v.inval_all := '0';
ptbl_rd := '0';
prtbl_rd := '0';
-- Radix tree data structures in memory are big-endian,
-- so we need to byte-swap them
for i in 0 to 7 loop
data(i * 8 + 7 downto i * 8) := d_in.data((7 - i) * 8 + 7 downto (7 - i) * 8);
end loop;
case r.state is
when IDLE =>
if l_in.addr(63) = '0' then
pgtbl := r.pgtbl0;
pt_valid := r.pt0_valid;
else
pgtbl := r.pgtbl3;
pt_valid := r.pt3_valid;
end if;
-- rts == radix tree size, # address bits being translated
rts := unsigned('0' & pgtbl(62 downto 61) & pgtbl(7 downto 5));
-- mbits == # address bits to index top level of tree
mbits := unsigned('0' & pgtbl(4 downto 0));
-- set v.shift to rts so that we can use finalmask for the segment check
v.shift := rts;
v.mask_size := mbits(4 downto 0);
v.pgbase := pgtbl(55 downto 8) & x"00";
if l_in.valid = '1' then
v.addr := l_in.addr;
v.iside := l_in.iside;
v.store := not (l_in.load or l_in.iside);
v.priv := l_in.priv;
if l_in.tlbie = '1' then
-- Invalidate all iTLB/dTLB entries for tlbie with
-- RB[IS] != 0 or RB[AP] != 0, or for slbia
v.inval_all := l_in.slbia or l_in.addr(11) or l_in.addr(10) or
l_in.addr(7) or l_in.addr(6) or l_in.addr(5);
-- RIC=2 or 3 flushes process table caches.
if l_in.ric(1) = '1' then
v.pt0_valid := '0';
v.pt3_valid := '0';
v.ptb_valid := '0';
end if;
v.state := DO_TLBIE;
else
v.valid := '1';
if r.ptb_valid = '0' then
-- need to fetch process table base from partition table
v.state := PART_TBL_READ;
elsif pt_valid = '0' then
-- need to fetch process table entry
-- set v.shift so we can use finalmask for generating
-- the process table entry address
v.shift := unsigned('0' & r.prtbl(4 downto 0));
v.state := PROC_TBL_READ;
elsif mbits = 0 then
-- Use RPDS = 0 to disable radix tree walks
v.state := RADIX_FINISH;
v.invalid := '1';
else
v.state := SEGMENT_CHECK;
end if;
end if;
end if;
if l_in.mtspr = '1' then
-- Move to PID needs to invalidate L1 TLBs and cached
-- pgtbl0 value. Move to PTCR does that plus
-- invalidating the cached pgtbl3 and prtbl values as well.
if l_in.sprnt = '0' then
v.pid := l_in.rs(31 downto 0);
else
v.ptcr := l_in.rs;
v.pt3_valid := '0';
v.ptb_valid := '0';
end if;
v.pt0_valid := '0';
v.inval_all := '1';
v.state := DO_TLBIE;
end if;
when DO_TLBIE =>
dcreq := '1';
tlbie_req := '1';
v.state := TLB_WAIT;
when TLB_WAIT =>
if d_in.done = '1' then
v.state := RADIX_FINISH;
end if;
when PART_TBL_READ =>
dcreq := '1';
ptbl_rd := '1';
v.state := PART_TBL_WAIT;
when PART_TBL_WAIT =>
if d_in.done = '1' then
v.prtbl := data;
v.ptb_valid := '1';
v.state := PART_TBL_DONE;
end if;
when PART_TBL_DONE =>
v.shift := unsigned('0' & r.prtbl(4 downto 0));
v.state := PROC_TBL_READ;
when PROC_TBL_READ =>
dcreq := '1';
prtbl_rd := '1';
v.state := PROC_TBL_WAIT;
when PROC_TBL_WAIT =>
if d_in.done = '1' then
if r.addr(63) = '1' then
v.pgtbl3 := data;
v.pt3_valid := '1';
else
v.pgtbl0 := data;
v.pt0_valid := '1';
end if;
-- rts == radix tree size, # address bits being translated
rts := unsigned('0' & data(62 downto 61) & data(7 downto 5));
-- mbits == # address bits to index top level of tree
mbits := unsigned('0' & data(4 downto 0));
-- set v.shift to rts so that we can use finalmask for the segment check
v.shift := rts;
v.mask_size := mbits(4 downto 0);
v.pgbase := data(55 downto 8) & x"00";
if mbits = 0 then
v.state := RADIX_FINISH;
v.invalid := '1';
else
v.state := SEGMENT_CHECK;
end if;
end if;
if d_in.err = '1' then
v.state := RADIX_FINISH;
v.badtree := '1';
end if;
when SEGMENT_CHECK =>
mbits := '0' & r.mask_size;
v.shift := r.shift + (31 - 12) - mbits;
nonzero := or(r.addr(61 downto 31) and not finalmask(30 downto 0));
if r.addr(63) /= r.addr(62) or nonzero = '1' then
v.state := RADIX_FINISH;
v.segerror := '1';
elsif mbits < 5 or mbits > 16 or mbits > (r.shift + (31 - 12)) then
v.state := RADIX_FINISH;
v.badtree := '1';
else
v.state := RADIX_LOOKUP;
end if;
when RADIX_LOOKUP =>
dcreq := '1';
v.state := RADIX_READ_WAIT;
when RADIX_READ_WAIT =>
if d_in.done = '1' then
v.pde := data;
-- test valid bit
if data(63) = '1' then
-- test leaf bit
if data(62) = '1' then
-- check permissions and RC bits
perm_ok := '0';
if r.priv = '1' or data(3) = '0' then
if r.iside = '0' then
perm_ok := data(1) or (data(2) and not r.store);
else
-- no IAMR, so no KUEP support for now
-- deny execute permission if cache inhibited
perm_ok := data(0) and not data(5);
end if;
end if;
rc_ok := data(8) and (data(7) or not r.store);
if perm_ok = '1' and rc_ok = '1' then
v.state := RADIX_LOAD_TLB;
else
v.state := RADIX_FINISH;
v.perm_err := not perm_ok;
-- permission error takes precedence over RC error
v.rc_error := perm_ok;
end if;
else
mbits := unsigned('0' & data(4 downto 0));
if mbits < 5 or mbits > 16 or mbits > r.shift then
v.state := RADIX_FINISH;
v.badtree := '1';
else
v.shift := v.shift - mbits;
v.mask_size := mbits(4 downto 0);
v.pgbase := data(55 downto 8) & x"00";
v.state := RADIX_LOOKUP;
end if;
end if;
else
-- non-present PTE, generate a DSI
v.state := RADIX_FINISH;
v.invalid := '1';
end if;
end if;
if d_in.err = '1' then
v.state := RADIX_FINISH;
v.badtree := '1';
end if;
when RADIX_LOAD_TLB =>
tlb_load := '1';
if r.iside = '0' then
dcreq := '1';
v.state := TLB_WAIT;
else
itlb_load := '1';
v.state := IDLE;
end if;
when RADIX_FINISH =>
v.state := IDLE;
end case;
if v.state = RADIX_FINISH or (v.state = RADIX_LOAD_TLB and r.iside = '1') then
v.err := v.invalid or v.badtree or v.segerror or v.perm_err or v.rc_error;
v.done := not v.err;
end if;
if r.addr(63) = '1' then
effpid := x"00000000";
else
effpid := r.pid;
end if;
prtable_addr := x"00" & r.prtbl(55 downto 36) &
((r.prtbl(35 downto 12) and not finalmask(23 downto 0)) or
(effpid(31 downto 8) and finalmask(23 downto 0))) &
effpid(7 downto 0) & "0000";
pgtable_addr := x"00" & r.pgbase(55 downto 19) &
((r.pgbase(18 downto 3) and not mask) or (addrsh and mask)) &
"000";
pte := x"00" &
((r.pde(55 downto 12) and not finalmask) or (r.addr(55 downto 12) and finalmask))
& r.pde(11 downto 0);
-- update registers
rin <= v;
-- drive outputs
if tlbie_req = '1' then
addr := r.addr;
tlb_data := (others => '0');
elsif tlb_load = '1' then
addr := r.addr(63 downto 12) & x"000";
tlb_data := pte;
elsif ptbl_rd = '1' then
addr := x"00" & r.ptcr(55 downto 12) & x"008";
tlb_data := (others => '0');
elsif prtbl_rd = '1' then
addr := prtable_addr;
tlb_data := (others => '0');
else
addr := pgtable_addr;
tlb_data := (others => '0');
end if;
l_out.done <= r.done;
l_out.err <= r.err;
l_out.invalid <= r.invalid;
l_out.badtree <= r.badtree;
l_out.segerr <= r.segerror;
l_out.perm_error <= r.perm_err;
l_out.rc_error <= r.rc_error;
d_out.valid <= dcreq;
d_out.tlbie <= tlbie_req;
d_out.doall <= r.inval_all;
d_out.tlbld <= tlb_load;
d_out.addr <= addr;
d_out.pte <= tlb_data;
i_out.tlbld <= itlb_load;
i_out.tlbie <= tlbie_req;
i_out.doall <= r.inval_all;
i_out.addr <= addr;
i_out.pte <= tlb_data;
end process;
end;