[edk2-devel] [PATCH v3 4/6] OvmfPkg/ResetVector: SEV: keep #vc handler installed longer

["Gerd Hoffmann" <kraxel@redhat.com>]

When running in SEV mode do not uninstall the #vc handler in
CheckSevFeatures.   Keep it active and uninstall it later in
SevClearPageEncMaskForGhcbPage.

This allows using the cpuid instruction in SetCr3ForPageTables64,
which is needed to check for la57 & 1G page support.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 OvmfPkg/ResetVector/Ia32/AmdSev.asm | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/OvmfPkg/ResetVector/Ia32/AmdSev.asm b/OvmfPkg/ResetVector/Ia32/AmdSev.asm
index 043c88a7abbe..02f287f1d934 100644
--- a/OvmfPkg/ResetVector/Ia32/AmdSev.asm
+++ b/OvmfPkg/ResetVector/Ia32/AmdSev.asm
@@ -158,6 +158,11 @@ SevClearPageEncMaskForGhcbPage:
     cmp       byte[WORK_AREA_GUEST_TYPE], 1
     jnz       SevClearPageEncMaskForGhcbPageExit
 
+    ; Clear exception handlers and stack
+    mov       eax, ADDR_OF(IdtrClear)
+    lidt      [cs:eax]
+    mov       esp, 0
+
     ; Check if SEV-ES is enabled
     mov       ecx, 1
     bt        [SEV_ES_WORK_AREA_STATUS_MSR], ecx
@@ -332,7 +337,6 @@ NoSevEsVcHlt:
 NoSevPass:
     xor       eax, eax
 
-SevExit:
     ;
     ; Clear exception handlers and stack
     ;
@@ -342,6 +346,7 @@ SevExit:
     pop       eax
     mov       esp, 0
 
+SevExit:
     OneTimeCallRet CheckSevFeatures
 
 ; Start of #VC exception handling routines
-- 
2.43.2



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