[edk2-devel] [PATCH v2 09/10] OvmfPkg/ResetVector: leave SEV VC handler installed longer

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

When running in SEV mode keep the VC handler installed.
Add a function to uninstall it later.

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       | 12 ++++++++++--
 OvmfPkg/ResetVector/Ia32/PageTables64.asm |  1 +
 OvmfPkg/ResetVector/Main.asm              |  4 ++++
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/OvmfPkg/ResetVector/Ia32/AmdSev.asm b/OvmfPkg/ResetVector/Ia32/AmdSev.asm
index 23e4c5ebbe92..cbb86871636f 100644
--- a/OvmfPkg/ResetVector/Ia32/AmdSev.asm
+++ b/OvmfPkg/ResetVector/Ia32/AmdSev.asm
@@ -320,9 +320,9 @@ NoSevEsVcHlt:
 NoSevPass:
     xor       eax, eax
 
-SevExit:
     ;
-    ; Clear exception handlers and stack
+    ; When NOT running in SEV mode: clear exception handlers and stack here.
+    ; Otherwise: SevClearVcHandlerAndStack must be called later.
     ;
     push      eax
     mov       eax, ADDR_OF(IdtrClear)
@@ -330,8 +330,16 @@ SevExit:
     pop       eax
     mov       esp, 0
 
+SevExit:
     OneTimeCallRet CheckSevFeatures
 
+SevClearVcHandlerAndStack:
+    ; Clear exception handlers and stack
+    mov       eax, ADDR_OF(IdtrClear)
+    lidt      [cs:eax]
+    mov       esp, 0
+    OneTimeCallRet SevClearVcHandlerAndStack
+
 ; Start of #VC exception handling routines
 ;
 
diff --git a/OvmfPkg/ResetVector/Ia32/PageTables64.asm b/OvmfPkg/ResetVector/Ia32/PageTables64.asm
index b922c845f297..29ce155eed8d 100644
--- a/OvmfPkg/ResetVector/Ia32/PageTables64.asm
+++ b/OvmfPkg/ResetVector/Ia32/PageTables64.asm
@@ -254,6 +254,7 @@ SevInit:
     CreatePageTables4Level edx
     ; Clear the C-bit from the GHCB page if the SEV-ES is enabled.
     OneTimeCall   SevClearPageEncMaskForGhcbPage
+    OneTimeCall   SevClearVcHandlerAndStack
     jmp SetCr3
 
 TdxBspInit:
diff --git a/OvmfPkg/ResetVector/Main.asm b/OvmfPkg/ResetVector/Main.asm
index 46cfa87c4c0a..88b25db3bc9e 100644
--- a/OvmfPkg/ResetVector/Main.asm
+++ b/OvmfPkg/ResetVector/Main.asm
@@ -80,7 +80,11 @@ SearchBfv:
     ; Set the OVMF/SEV work area as appropriate.
     ;
     OneTimeCall CheckSevFeatures
+    cmp         byte[WORK_AREA_GUEST_TYPE], 1
+    jnz         NoSevIa32
+    OneTimeCall SevClearVcHandlerAndStack
 
+NoSevIa32:
     ;
     ; Restore initial EAX value into the EAX register
     ;
-- 
2.44.0



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