BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198

Under SEV-ES, a MONITOR/MONITORX intercept generates a #VC exception.
VMGEXIT must be used to allow the hypervisor to handle this intercept.

Cc: Eric Dong <eric.dong@...>
Cc: Ray Ni <ray.ni@...>
Cc: Laszlo Ersek <lersek@...>
Signed-off-by: Tom Lendacky <thomas.lendacky@...>
---
.../X64/ArchAMDSevVcHandler.c | 31 +++++++++++++++++++
1 file changed, 31 insertions(+)

diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ArchAMDSevVcHandler.c b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ArchAMDSevVcHandler.c
index 0a27ade69310..784229c5ca8d 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ArchAMDSevVcHandler.c
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ArchAMDSevVcHandler.c
@@ -591,6 +591,33 @@ MmioExit (
return Status;
}

+STATIC
+UINT64
+MonitorExit (
+ GHCB *Ghcb,
+ EFI_SYSTEM_CONTEXT_X64 *Regs,
+ SEV_ES_INSTRUCTION_DATA *InstructionData
+ )
+{
+ UINT64 Status;
+
+ DecodeModRm (Regs, InstructionData);
+
+ Ghcb->SaveArea.Rax = Regs->Rax; // Identity mapped, so VA = PA
+ GhcbSetRegValid (Ghcb, GhcbRax);
+ Ghcb->SaveArea.Rcx = Regs->Rcx;
+ GhcbSetRegValid (Ghcb, GhcbRcx);
+ Ghcb->SaveArea.Rdx = Regs->Rdx;
+ GhcbSetRegValid (Ghcb, GhcbRdx);
+
+ Status = VmgExit (Ghcb, SvmExitMonitor, 0, 0);
+ if (Status) {
+ return Status;
+ }
+
+ return 0;
+}
+
STATIC
UINT64
WbinvdExit (
@@ -1076,6 +1103,10 @@ DoVcCommon (
NaeExit = WbinvdExit;
break;

+ case SvmExitMonitor:
+ NaeExit = MonitorExit;
+ break;
+
case SvmExitNpf:
NaeExit = MmioExit;
break;
--
2.17.1