[PATCH v4 12/40] UefiCpuPkg/CpuExceptionHandler: Add support for MSR_PROT NAE events


Lendacky, Thomas
 

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: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
.../X64/AMDSevVcCommon.c | 49 +++++++++++++++++++
1 file changed, 49 insertions(+)

diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/AMDSevVcCommon.c b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/AMDSevVcCommon.c
index 90541c9a0390..25bcc34218d7 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/AMDSevVcCommon.c
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/AMDSevVcCommon.c
@@ -294,6 +294,51 @@ UnsupportedExit (
return Status;
}

+STATIC
+UINT64
+MsrExit (
+ GHCB *Ghcb,
+ EFI_SYSTEM_CONTEXT_X64 *Regs,
+ 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);
+ /* Fallthrough */
+ case 0x32: // RDMSR
+ Ghcb->SaveArea.Rcx = Regs->Rcx;
+ GhcbSetRegValid (Ghcb, GhcbRcx);
+ break;
+ default:
+ return UnsupportedExit (Ghcb, Regs, InstructionData);
+ }
+
+ Status = VmgExit (Ghcb, SvmExitMsr, ExitInfo1, 0);
+ if (Status) {
+ return Status;
+ }
+
+ if (!ExitInfo1) {
+ if (!GhcbIsRegValid (Ghcb, GhcbRax) ||
+ !GhcbIsRegValid (Ghcb, GhcbRdx)) {
+ return UnsupportedExit (Ghcb, Regs, InstructionData);
+ }
+ Regs->Rax = Ghcb->SaveArea.Rax;
+ Regs->Rdx = Ghcb->SaveArea.Rdx;
+ }
+
+ return 0;
+}
+
#define IOIO_TYPE_STR (1 << 2)
#define IOIO_TYPE_IN 1
#define IOIO_TYPE_INS (IOIO_TYPE_IN | IOIO_TYPE_STR)
@@ -558,6 +603,10 @@ DoVcCommon (
NaeExit = IoioExit;
break;

+ case SvmExitMsr:
+ NaeExit = MsrExit;
+ break;
+
default:
NaeExit = UnsupportedExit;
}
--
2.17.1

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