execute1: Implement LPCR[EVIRT] bit

This implements the EVIRT bit in the LPCR register.  When set to 1,
EVIRT causes mfspr and mtspr to an undefined SPR number in privileged
mode (i.e. hypervisor mode) to cause a hypervisor emulation assistance
interrupt.  When set to 0, such instructions are executed as no-ops.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

common.vhdl

@@ -249,6 +249,7 @@ package common is
     -- LPCR bit numbers
     constant LPCR_HAIL    : integer := 63 - 37;
     constant LPCR_UPRT    : integer := 63 - 41;
+    constant LPCR_EVIRT   : integer := 63 - 42;
     constant LPCR_HR      : integer := 63 - 43;
     constant LPCR_LD      : integer := 63 - 46;
     constant LPCR_HEIC    : integer := 63 - 59;
@@ -322,6 +323,7 @@ package common is
         hdexcr_hyp: aspect_bits_t;
         hdexcr_enf: aspect_bits_t;
         lpcr_hail: std_ulogic;
+        lpcr_evirt: std_ulogic;
         lpcr_ld: std_ulogic;
         lpcr_heic: std_ulogic;
         lpcr_lpes: std_ulogic;
@@ -333,7 +335,7 @@ package common is
          dscr => (others => '0'),
          dexcr_pnh => aspect_bits_init, dexcr_pro => aspect_bits_init,
          hdexcr_hyp => aspect_bits_init, hdexcr_enf => aspect_bits_init,
-         lpcr_hail => '0', lpcr_ld => '1', lpcr_heic => '0',
+         lpcr_hail => '0', lpcr_evirt => '0', lpcr_ld => '1', lpcr_heic => '0',
          lpcr_lpes => '0', lpcr_hvice => '0',
          others => (others => '0'));
 

execute1.vhdl

@@ -425,6 +425,7 @@ architecture behaviour of execute1 is
     begin
         ret := (others => '0');
         ret(LPCR_HAIL) := c.lpcr_hail;
+        ret(LPCR_EVIRT) := c.lpcr_evirt;
         ret(LPCR_UPRT) := '1';
         ret(LPCR_HR) := '1';
         ret(LPCR_LD) := c.lpcr_ld;
@@ -1450,14 +1451,15 @@ begin
                     end if;
                 else
                     -- mfspr from unimplemented SPRs should be a nop in
-                    -- supervisor mode and a program interrupt for user mode
+                    -- supervisor mode and a program or HEAI interrupt for user mode
+                    -- LPCR[EVIRT] = 1 makes it HEAI in privileged mode
                     if e_in.valid = '1' and not is_X(e_in.insn) then
                         report "MFSPR to SPR " & integer'image(decode_spr_num(e_in.insn)) &
                             " invalid";
                     end if;
                     slow_op := '1';
                     v.e.write_enable := '0';
-                    if ex1.msr(MSR_PR) = '1' then
+                    if ex1.msr(MSR_PR) = '1' or ctrl.lpcr_evirt = '1' then
                         illegal := '1';
                     end if;
                 end if;
@@ -1544,8 +1546,9 @@ begin
                 end if;
 		if e_in.spr_select.valid = '0' and e_in.spr_is_ram = '0' then
                     -- mtspr to unimplemented SPRs should be a nop in
-                    -- supervisor mode and a program interrupt for user mode
-                    if ex1.msr(MSR_PR) = '1' then
+                    -- supervisor mode and a program interrupt or HEAI for user mode
+                    -- LPCR[EVIRT] = 1 makes it HEAI in privileged mode
+                    if ex1.msr(MSR_PR) = '1' or ctrl.lpcr_evirt = '1' then
                         illegal := '1';
                     end if;
 		end if;
@@ -2185,6 +2188,7 @@ begin
             end if;
             if ex1.se.write_lpcr = '1' then
                 ctrl_tmp.lpcr_hail <= ex1.spr_write_data(LPCR_HAIL);
+                ctrl_tmp.lpcr_evirt <= ex1.spr_write_data(LPCR_EVIRT);
                 ctrl_tmp.lpcr_ld <= ex1.spr_write_data(LPCR_LD);
                 ctrl_tmp.lpcr_heic <= ex1.spr_write_data(LPCR_HEIC);
                 ctrl_tmp.lpcr_lpes <= ex1.spr_write_data(LPCR_LPES);