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OvmfPkg/VmgExitLib: Add support for MSR_PROT NAE events 

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.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 6587e08d3a
commit 9711c9230b
1 changed files with 65 additions and 0 deletions
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65
OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c
View File

@ -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
@retval 0 Event handled successfully
@return 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;
}