On 9/23/20 3:32 PM, Sean Christopherson wrote:
> On Wed, Sep 23, 2020 at 03:27:39PM -0500, Tom Lendacky wrote:
>> From: Tom Lendacky <thomas.lendacky@xxxxxxx>
>>
>> The INVD instruction intercept performs emulation. Emulation can't be done
>> on an SEV guest because the guest memory is encrypted.
>>
>> Provide a dedicated intercept routine for the INVD intercept. Within this
>> intercept routine just skip the instruction for an SEV guest, since it is
>> emulated as a NOP anyway.
>>
>> Fixes: 1654efcbc431 ("KVM: SVM: Add KVM_SEV_INIT command")
>> Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
>> ---
>> arch/x86/kvm/svm/svm.c | 13 ++++++++++++-
>> 1 file changed, 12 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
>> index c91acabf18d0..332ec4425d89 100644
>> --- a/arch/x86/kvm/svm/svm.c
>> +++ b/arch/x86/kvm/svm/svm.c
>> @@ -2183,6 +2183,17 @@ static int iret_interception(struct vcpu_svm *svm)
>> return 1;
>> }
>>
>> +static int invd_interception(struct vcpu_svm *svm)
>> +{
>> + /*
>> + * Can't do emulation on an SEV guest and INVD is emulated
>> + * as a NOP, so just skip the instruction.
>> + */
>> + return (sev_guest(svm->vcpu.kvm))
>> + ? kvm_skip_emulated_instruction(&svm->vcpu)
>> + : kvm_emulate_instruction(&svm->vcpu, 0);
>
> Is there any reason not to do kvm_skip_emulated_instruction() for both SEV
> and legacy? VMX has the same odd kvm_emulate_instruction() call, but AFAICT
> that's completely unecessary, i.e. VMX can also convert to a straight skip.
You could, I just figured I'd leave the legacy behavior just in case. Not
that I can think of a reason that behavior would ever change.
Thanks,
Tom
>
>> +}
>> +
>> static int invlpg_interception(struct vcpu_svm *svm)
>> {
>> if (!static_cpu_has(X86_FEATURE_DECODEASSISTS))
>> @@ -2774,7 +2785,7 @@ static int (*const svm_exit_handlers[])(struct vcpu_svm *svm) = {
>> [SVM_EXIT_RDPMC] = rdpmc_interception,
>> [SVM_EXIT_CPUID] = cpuid_interception,
>> [SVM_EXIT_IRET] = iret_interception,
>> - [SVM_EXIT_INVD] = emulate_on_interception,
>> + [SVM_EXIT_INVD] = invd_interception,
>> [SVM_EXIT_PAUSE] = pause_interception,
>> [SVM_EXIT_HLT] = halt_interception,
>> [SVM_EXIT_INVLPG] = invlpg_interception,
>> --
>> 2.28.0
>>
