On 5/22/20 5:31 AM, Laszlo Ersek wrote:
> On 05/19/20 23:50, Lendacky, Thomas wrote:
>> BZ: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugzilla.tianocore.org%2Fshow_bug.cgi%3Fid%3D2198&data=02%7C01%7Cthomas.lendacky%40amd.com%7C95b407c13bd44ad1b89608d7fe3b450a%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637257402837183063&sdata=jSpUywdrvuJ5Iw1lfVb30VUuZc%2FBOGn%2B670DymPBePY%3D&reserved=0
>>
>> 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>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
>> ---
>> .../Library/VmgExitLib/X64/VmgExitVcHandler.c | 63 +++++++++++++++++++
>> 1 file changed, 63 insertions(+)
>>
>> diff --git a/OvmfPkg/Library/VmgExitLib/X64/VmgExitVcHandler.c b/OvmfPkg/Library/VmgExitLib/X64/VmgExitVcHandler.c
>> index 2f62795edf61..1c6b472a47c4 100644
>> --- a/OvmfPkg/Library/VmgExitLib/X64/VmgExitVcHandler.c
>> +++ b/OvmfPkg/Library/VmgExitLib/X64/VmgExitVcHandler.c
>> @@ -411,6 +411,65 @@ 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
>> + @retval 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
>
> This comment looks great!
>
>> + ExitInfo1 = 1;
>> + Ghcb->SaveArea.Rax = Regs->Rax;
>> + GhcbSetRegValid (Ghcb, GhcbRax);
>> + Ghcb->SaveArea.Rdx = Regs->Rdx;
>> + GhcbSetRegValid (Ghcb, GhcbRdx);
>> + /* Fallthrough */
>
> (1) This comment is very appreciated (I vaguely remember that the coding
> style actually requires it), but we're supposed to put it like this:
>
> //
> // fall through
> //
>
> (See: "git grep -B1 -A1 -i 'fall through'".)
>
Will do.
>> + 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) {
>
> (2) As usual, please check (Status > 0) or (Status != 0) explicitly.
Yup.
>
> Acked-by: Laszlo Ersek <lersek@redhat.com>
Thanks!
Tom
>
> Thanks
> Laszlo
>
>> + 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)
>> @@ -743,6 +802,10 @@ VmgExitHandleVc (
>> NaeExit = IoioExit;
>> break;
>>
>> + case SVM_EXIT_MSR:
>> + NaeExit = MsrExit;
>> + break;
>> +
>> default:
>> NaeExit = UnsupportedExit;
>> }
>>
>
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