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


Brijesh Singh
 

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