BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3275
The upcoming SEV-SNP support will need to make a few additional MSR
protocol based VMGEXIT's. Add a macro that wraps the common setup and
response validation logic in one place to keep the code readable.
While at it, define SEV_STATUS_MSR that will be used to get the SEV STATUS
MSR instead of open coding it.
Cc: James Bottomley <j...@linux.ibm.com>
Cc: Min Xu <min.m...@intel.com>
Cc: Jiewen Yao <jiewen....@intel.com>
Cc: Tom Lendacky <thomas.lenda...@amd.com>
Cc: Jordan Justen <jordan.l.jus...@intel.com>
Cc: Ard Biesheuvel <ardb+tianoc...@kernel.org>
Cc: Laszlo Ersek <ler...@redhat.com>
Cc: Erdem Aktas <erdemak...@google.com>
Suggested-by: Laszlo Ersek <ler...@redhat.com>
Signed-off-by: Brijesh Singh <brijesh.si...@amd.com>
---
OvmfPkg/ResetVector/Ia32/AmdSev.asm | 69 +++++++++++++++++++----------
1 file changed, 45 insertions(+), 24 deletions(-)
diff --git a/OvmfPkg/ResetVector/Ia32/AmdSev.asm
b/OvmfPkg/ResetVector/Ia32/AmdSev.asm
index b32dd3b5d656..c3b4e16bf681 100644
--- a/OvmfPkg/ResetVector/Ia32/AmdSev.asm
+++ b/OvmfPkg/ResetVector/Ia32/AmdSev.asm
@@ -35,6 +35,42 @@ BITS 32
%define GHCB_CPUID_REGISTER_SHIFT 30
%define CPUID_INSN_LEN 2
+%define SEV_STATUS_MSR 0xc0010130
+
+; 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
+; code. If it does not match then terminate the guest. The result of request
+; is returned in the EDX:EAX.
+;
+; args 1:Request code, 2: Response code
+%macro VmgExit 2
+ ;
+ ; Add request code:
+ ; GHCB_MSR[11:0] = Request code
+ or eax, %1
+
+ mov ecx, SEV_STATUS_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
+
+ mov ecx, SEV_STATUS_MSR
+ rdmsr
+
+ ;
+ ; Verify the reponse code, if it does not match then request to terminate
+ ; GHCB_MSR[11:0] = Response code
+ mov ecx, eax
+ and ecx, 0xfff
+ cmp ecx, %2
+ jne SevEsUnexpectedRespTerminate
+%endmacro
; Check if Secure Encrypted Virtualization (SEV) features are enabled.
;
@@ -85,7 +121,7 @@ CheckSevFeatures:
; Check if SEV memory encryption is enabled
; MSR_0xC0010131 - Bit 0 (SEV enabled)
- mov ecx, 0xc0010131
+ mov ecx, SEV_STATUS_MSR
rdmsr
bt eax, 0
jnc NoSev
@@ -100,7 +136,7 @@ CheckSevFeatures:
; Check if SEV-ES is enabled
; MSR_0xC0010131 - Bit 1 (SEV-ES enabled)
- mov ecx, 0xc0010131
+ mov ecx, SEV_STATUS_MSR
rdmsr
bt eax, 1
jnc GetSevEncBit
@@ -197,10 +233,10 @@ SevEsIdtNotCpuid:
mov eax, 1
jmp SevEsIdtTerminate
-SevEsIdtNoCpuidResponse:
+SevEsUnexpectedRespTerminate:
;
; Use VMGEXIT to request termination.
- ; 2 - GHCB_CPUID_RESPONSE not received
+ ; 2 - Unexpected Response is received
;
mov eax, 2
@@ -216,7 +252,7 @@ SevEsIdtTerminate:
shl eax, 16
or eax, 0x1100
xor edx, edx
- mov ecx, 0xc0010130
+ mov ecx, SEV_STATUS_MSR
wrmsr
;
; Issue VMGEXIT - NASM doesn't support the vmmcall instruction in 32-bit
@@ -276,7 +312,7 @@ SevEsIdtVmmComm:
mov [esp + VC_CPUID_REQUEST_REGISTER], eax
; Save current GHCB MSR value
- mov ecx, 0xc0010130
+ mov ecx, SEV_STATUS_MSR
rdmsr
mov [esp + VC_GHCB_MSR_EAX], eax
mov [esp + VC_GHCB_MSR_EDX], edx
@@ -293,31 +329,16 @@ NextReg:
jge VmmDone
shl eax, GHCB_CPUID_REGISTER_SHIFT
- or eax, GHCB_CPUID_REQUEST
mov edx, [esp + VC_CPUID_FUNCTION]
- mov ecx, 0xc0010130
- 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
+ VmgExit GHCB_CPUID_REQUEST, GHCB_CPUID_RESPONSE
;
- ; Read GHCB MSR
+ ; Response GHCB MSR
; GHCB_MSR[63:32] = CPUID register value
; GHCB_MSR[31:30] = CPUID register
; GHCB_MSR[11:0] = CPUID response protocol
;
- mov ecx, 0xc0010130
- rdmsr
- mov ecx, eax
- and ecx, 0xfff
- cmp ecx, GHCB_CPUID_RESPONSE
- jne SevEsIdtNoCpuidResponse
; Save returned value
shr eax, GHCB_CPUID_REGISTER_SHIFT
@@ -335,7 +356,7 @@ VmmDone:
;
mov eax, [esp + VC_GHCB_MSR_EAX]
mov edx, [esp + VC_GHCB_MSR_EDX]
- mov ecx, 0xc0010130
+ mov ecx, SEV_STATUS_MSR
wrmsr
mov eax, [esp + VC_CPUID_RESULT_EAX]
--
2.17.1
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