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OvmfPkg/VmgExitLib: Add support for CPUID NAE events 

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 (CPUID_EXTENDED_STATE) requires
XCR0 to be supplied in the GHCB, so add support to issue the XGETBV
instruction.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Regression-tested-by: Laszlo Ersek <lersek@redhat.com>
This commit is contained in:
Tom Lendacky 2020-08-12 15:21:37 -05:00 committed by mergify[bot]
parent 0020157a98
commit 6587e08d3a
1 changed files with 60 additions and 0 deletions
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60
OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c
View File

@ -11,6 +11,7 @@
#include <Library/BaseMemoryLib.h>
#include <Library/VmgExitLib.h>
#include <Register/Amd/Msr.h>
#include <Register/Intel/Cpuid.h>
#include <IndustryStandard/InstructionParsing.h>
//
@ -597,6 +598,61 @@ IoioExit (
return 0;
}
/**
Handle a CPUID event.
Use the VMGEXIT instruction to handle a CPUID 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
@retval 0 Event handled successfully
@return New exception value to propagate
**/
STATIC
UINT64
CpuidExit (
IN OUT GHCB *Ghcb,
IN OUT EFI_SYSTEM_CONTEXT_X64 *Regs,
IN 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 == CPUID_EXTENDED_STATE) {
IA32_CR4 Cr4;
Cr4.UintN = AsmReadCr4 ();
Ghcb->SaveArea.XCr0 = (Cr4.Bits.OSXSAVE == 1) ? AsmXGetBv (0) : 1;
GhcbSetRegValid (Ghcb, GhcbXCr0);
}
Status = VmgExit (Ghcb, SVM_EXIT_CPUID, 0, 0);
if (Status != 0) {
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;
}
/**
Handle a #VC exception.
@ -641,6 +697,10 @@ VmgExitHandleVc (
ExitCode = Regs->ExceptionData;
switch (ExitCode) {
case SVM_EXIT_CPUID:
NaeExit = CpuidExit;
break;
case SVM_EXIT_IOIO_PROT:
NaeExit = IoioExit;
break;