[PATCH 3/3] OvmfPkg/ResetVector: add the macro to request guest termination

["Brijesh Singh" <brijesh.singh@amd.com>]

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3275

The upcoming SEV-SNP support will need to make a few additional guest
termination requests depending on the failure type. Let's move the logic
to request the guest termination into a macro to keep the code readable.

Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Suggested-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 OvmfPkg/ResetVector/Ia32/AmdSev.asm | 87 +++++++++++++++--------------
 1 file changed, 45 insertions(+), 42 deletions(-)

diff --git a/OvmfPkg/ResetVector/Ia32/AmdSev.asm b/OvmfPkg/ResetVector/Ia32/AmdSev.asm
index 2c478cda314b..c4c00056f9f3 100644
--- a/OvmfPkg/ResetVector/Ia32/AmdSev.asm
+++ b/OvmfPkg/ResetVector/Ia32/AmdSev.asm
@@ -39,6 +39,13 @@ BITS    32
 %define SEV_GHCB_MSR                0xc0010130
 %define SEV_STATUS_MSR              0xc0010131
 
+; The #VC was not for CPUID
+%define TERM_VC_NOT_CPUID           1
+
+; The unexpected response code
+%define TERM_UNEXPECTED_RESP_CODE   2
+
+
 ; Macro is used to issue the MSR protocol based VMGEXIT. The caller is
 ; responsible to populate values in the EDX:EAX registers. After the vmmcall
 ; returns, it verifies that the response code matches with the expected
@@ -74,6 +81,43 @@ BITS    32
     jne     SevEsUnexpectedRespTerminate
 %endmacro
 
+; Macro to terminate the guest using the VMGEXIT.
+; arg 1: reason code
+%macro TerminateVmgExit 1
+    mov     eax, %1
+    ;
+    ; Use VMGEXIT to request termination. At this point the reason code is
+    ; located in EAX, so shift it left 16 bits to the proper location.
+    ;
+    ; EAX[11:0]  => 0x100 - request termination
+    ; EAX[15:12] => 0x1   - OVMF
+    ; EAX[23:16] => 0xXX  - REASON CODE
+    ;
+    shl     eax, 16
+    or      eax, 0x1100
+    xor     edx, edx
+    mov     ecx, SEV_GHCB_MSR
+    wrmsr
+    ;
+    ; Issue VMGEXIT - NASM doesn't support the vmmcall instruction in 32-bit
+    ; mode, so work around this by temporarily switching to 64-bit mode.
+    ;
+BITS    64
+    rep     vmmcall
+BITS    32
+
+    ;
+    ; We shouldn't come back from the VMGEXIT, but if we do, just loop.
+    ;
+%%TerminateHlt:
+    hlt
+    jmp     %%TerminateHlt
+%endmacro
+
+; Terminate the guest due to unexpected response code.
+SevEsUnexpectedRespTerminate:
+    TerminateVmgExit    TERM_UNEXPECTED_RESP_CODE
+
 ; Check if Secure Encrypted Virtualization (SEV) features are enabled.
 ;
 ; Register usage is tight in this routine, so multiple calls for the
@@ -228,48 +272,7 @@ SevEsDisabled:
 ;
 
 SevEsIdtNotCpuid:
-    ;
-    ; Use VMGEXIT to request termination.
-    ;   1 - #VC was not for CPUID
-    ;
-    mov     eax, 1
-    jmp     SevEsIdtTerminate
-
-SevEsUnexpectedRespTerminate:
-    ;
-    ; Use VMGEXIT to request termination.
-    ;   2 - Unexpected Response is received
-    ;
-    mov     eax, 2
-
-SevEsIdtTerminate:
-    ;
-    ; Use VMGEXIT to request termination. At this point the reason code is
-    ; located in EAX, so shift it left 16 bits to the proper location.
-    ;
-    ; EAX[11:0]  => 0x100 - request termination
-    ; EAX[15:12] => 0x1   - OVMF
-    ; EAX[23:16] => 0xXX  - REASON CODE
-    ;
-    shl     eax, 16
-    or      eax, 0x1100
-    xor     edx, edx
-    mov     ecx, SEV_GHCB_MSR
-    wrmsr
-    ;
-    ; Issue VMGEXIT - NASM doesn't support the vmmcall instruction in 32-bit
-    ; mode, so work around this by temporarily switching to 64-bit mode.
-    ;
-BITS    64
-    rep     vmmcall
-BITS    32
-
-    ;
-    ; We shouldn't come back from the VMGEXIT, but if we do, just loop.
-    ;
-SevEsIdtHlt:
-    hlt
-    jmp     SevEsIdtHlt
+    TerminateVmgExit TERM_VC_NOT_CPUID
     iret
 
     ;
-- 
2.17.1