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

In preparation for SEV-SNP support move clearing of the GHCB memory from
the ResetVector/AmdSev.asm to SecMain/AmdSev.c. The GHCB page is not
accessed until SevEsProtocolCheck() switch to full GHCB. So, the move
does not make any changes in the code flow or logic. The move will
simplify the SEV-SNP support.

Cc: Michael Roth <[email protected]>
Cc: James Bottomley <[email protected]>
Cc: Min Xu <[email protected]>
Cc: Jiewen Yao <[email protected]>
Cc: Tom Lendacky <[email protected]>
Cc: Jordan Justen <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Erdem Aktas <[email protected]>
Cc: Gerd Hoffmann <[email protected]>
Signed-off-by: Brijesh Singh <[email protected]>
---
 OvmfPkg/Sec/AmdSev.c                | 2 +-
 OvmfPkg/ResetVector/Ia32/AmdSev.asm | 6 ------
 2 files changed, 1 insertion(+), 7 deletions(-)

diff --git a/OvmfPkg/Sec/AmdSev.c b/OvmfPkg/Sec/AmdSev.c
index 3b4adaae32c7..7f74e8bfe88e 100644
--- a/OvmfPkg/Sec/AmdSev.c
+++ b/OvmfPkg/Sec/AmdSev.c
@@ -95,7 +95,7 @@ SevEsProtocolCheck (
   AsmWriteMsr64 (MSR_SEV_ES_GHCB, Msr.GhcbPhysicalAddress);
 
   Ghcb = Msr.Ghcb;
-  SetMem (Ghcb, sizeof (*Ghcb), 0);
+  SetMem (Ghcb, FixedPcdGet32 (PcdOvmfSecGhcbSize), 0);
 
   //
   // Set the version to the maximum that can be supported
diff --git a/OvmfPkg/ResetVector/Ia32/AmdSev.asm 
b/OvmfPkg/ResetVector/Ia32/AmdSev.asm
index 250ac8d8b180..48d9178168b0 100644
--- a/OvmfPkg/ResetVector/Ia32/AmdSev.asm
+++ b/OvmfPkg/ResetVector/Ia32/AmdSev.asm
@@ -177,12 +177,6 @@ pageTableEntries4kLoop:
     mov     ecx, (GHCB_BASE & 0x1F_FFFF) >> 12
     mov     [ecx * 8 + GHCB_PT_ADDR + 4], strict dword 0
 
-    mov     ecx, GHCB_SIZE / 4
-    xor     eax, eax
-clearGhcbMemoryLoop:
-    mov     dword[ecx * 4 + GHCB_BASE - 4], eax
-    loop    clearGhcbMemoryLoop
-
 SevClearPageEncMaskForGhcbPageExit:
     OneTimeCallRet SevClearPageEncMaskForGhcbPage
 
-- 
2.25.1



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