[PATCH v5 13/42] UefiCpuPkg/CpuExceptionHandler: Add support for CPUID NAE events


Lendacky, Thomas
 

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

Under SEV-ES, a CPUID 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 a CPUID NAE
event. Additionally, CPUID 0x0000_000d requires XCR0 to be supplied in
the GHCB, so add support to issue the XGETBV instruction.

Cc: Eric Dong <eric.dong@...>
Cc: Ray Ni <ray.ni@...>
Cc: Laszlo Ersek <lersek@...>
Signed-off-by: Tom Lendacky <thomas.lendacky@...>
---
.../X64/ArchAMDSevVcHandler.c | 44 +++++++++++++++++++
1 file changed, 44 insertions(+)

diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ArchAMDSevVcHandler.c b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ArchAMDSevVcHandler.c
index 28adf0d5e9c4..970ee8752253 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ArchAMDSevVcHandler.c
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ArchAMDSevVcHandler.c
@@ -11,6 +11,8 @@
#include <Library/VmgExitLib.h>
#include "AMDSevVcCommon.h"

+#define CR4_OSXSAVE (1 << 18)
+
typedef enum {
LongMode64Bit = 0,
LongModeCompat32Bit,
@@ -494,6 +496,44 @@ IoioExit (
return 0;
}

+STATIC
+UINT64
+CpuidExit (
+ GHCB *Ghcb,
+ EFI_SYSTEM_CONTEXT_X64 *Regs,
+ SEV_ES_INSTRUCTION_DATA *InstructionData
+ )
+{
+ UINT64 Status;
+
+ Ghcb->SaveArea.Rax = Regs->Rax;
+ GhcbSetRegValid (Ghcb, GhcbRax);
+ Ghcb->SaveArea.Rcx = Regs->Rcx;
+ GhcbSetRegValid (Ghcb, GhcbRcx);
+ if (Regs->Rax == 0x0000000d) {
+ Ghcb->SaveArea.XCr0 = (AsmReadCr4 () & CR4_OSXSAVE) ? AsmXGetBv (0) : 1;
+ GhcbSetRegValid (Ghcb, GhcbXCr0);
+ }
+
+ Status = VmgExit (Ghcb, SvmExitCpuid, 0, 0);
+ if (Status) {
+ return Status;
+ }
+
+ if (!GhcbIsRegValid (Ghcb, GhcbRax) ||
+ !GhcbIsRegValid (Ghcb, GhcbRbx) ||
+ !GhcbIsRegValid (Ghcb, GhcbRcx) ||
+ !GhcbIsRegValid (Ghcb, GhcbRdx)) {
+ return UnsupportedExit (Ghcb, Regs, InstructionData);
+ }
+ Regs->Rax = Ghcb->SaveArea.Rax;
+ Regs->Rbx = Ghcb->SaveArea.Rbx;
+ Regs->Rcx = Ghcb->SaveArea.Rcx;
+ Regs->Rdx = Ghcb->SaveArea.Rdx;
+
+ return 0;
+}
+
UINTN
DoVcCommon (
GHCB *Ghcb,
@@ -510,6 +550,10 @@ DoVcCommon (

ExitCode = Regs->ExceptionData;
switch (ExitCode) {
+ case SvmExitCpuid:
+ NaeExit = CpuidExit;
+ break;
+
case SvmExitIoioProt:
NaeExit = IoioExit;
break;
--
2.17.1

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