BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198
Under SEV-ES, a MSR_PROT intercept generates a #VC exception. VMGEXIT must
be used to allow the hypervisor to handle this intercept.
Add support to construct the required GHCB values to support an MSR_PROT
NAE event. Parse the instruction that generated the #VC exception to
determine whether it is RDMSR or WRMSR, setting the required register
register values in the GHCB and creating the proper SW_EXIT_INFO1 value in
the GHCB.
Cc: Jordan Justen <jordan.l.jus...@intel.com>
Cc: Laszlo Ersek <ler...@redhat.com>
Cc: Ard Biesheuvel <ard.biesheu...@arm.com>
Acked-by: Laszlo Ersek <ler...@redhat.com>
Signed-off-by: Tom Lendacky <thomas.lenda...@amd.com>
---
OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c | 65 ++++++++++++++++++++
1 file changed, 65 insertions(+)
diff --git a/OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c
b/OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c
index 1e0b2bf399da..009eb48cd468 100644
--- a/OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c
+++ b/OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c
@@ -374,6 +374,67 @@ UnsupportedExit (
return Status;
}
+/**
+ Handle an MSR event.
+
+ Use the VMGEXIT instruction to handle either a RDMSR or WRMSR event.
+
+ @param[in, out] Ghcb Pointer to the Guest-Hypervisor
Communication
+ Block
+ @param[in, out] Regs x64 processor context
+ @param[in] InstructionData Instruction parsing context
+
+ @return 0 Event handled successfully
+ @return Others New exception value to propagate
+
+**/
+STATIC
+UINT64
+MsrExit (
+ IN OUT GHCB *Ghcb,
+ IN OUT EFI_SYSTEM_CONTEXT_X64 *Regs,
+ IN SEV_ES_INSTRUCTION_DATA *InstructionData
+ )
+{
+ UINT64 ExitInfo1, Status;
+
+ ExitInfo1 = 0;
+
+ switch (*(InstructionData->OpCodes + 1)) {
+ case 0x30: // WRMSR
+ ExitInfo1 = 1;
+ Ghcb->SaveArea.Rax = Regs->Rax;
+ GhcbSetRegValid (Ghcb, GhcbRax);
+ Ghcb->SaveArea.Rdx = Regs->Rdx;
+ GhcbSetRegValid (Ghcb, GhcbRdx);
+ //
+ // fall through
+ //
+ case 0x32: // RDMSR
+ Ghcb->SaveArea.Rcx = Regs->Rcx;
+ GhcbSetRegValid (Ghcb, GhcbRcx);
+ break;
+ default:
+ return UnsupportedExit (Ghcb, Regs, InstructionData);
+ }
+
+ Status = VmgExit (Ghcb, SVM_EXIT_MSR, ExitInfo1, 0);
+ if (Status != 0) {
+ return Status;
+ }
+
+ if (ExitInfo1 == 0) {
+ if (!GhcbIsRegValid (Ghcb, GhcbRax) ||
+ !GhcbIsRegValid (Ghcb, GhcbRdx)) {
+ return UnsupportedExit (Ghcb, Regs, InstructionData);
+ }
+ Regs->Rax = Ghcb->SaveArea.Rax;
+ Regs->Rdx = Ghcb->SaveArea.Rdx;
+ }
+
+ return 0;
+}
+
/**
Build the IOIO event information.
@@ -705,6 +766,10 @@ VmgExitHandleVc (
NaeExit = IoioExit;
break;
+ case SVM_EXIT_MSR:
+ NaeExit = MsrExit;
+ break;
+
default:
NaeExit = UnsupportedExit;
}
--
2.27.0
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