Re: [PATCH v3 5/7] KVM: SVM: Handle vectoring error in check_emulate_instruction
From: Sean Christopherson
Date: Wed Dec 18 2024 - 13:41:00 EST
On Tue, Dec 17, 2024, Ivan Orlov wrote:
> Detect unhandleable vectoring in check_emulate_instruction to prevent
> infinite loop on SVM and eliminate the difference in how intercepted #PF
> during vectoring is handled on SVM and VMX.
>
> Signed-off-by: Ivan Orlov <iorlov@xxxxxxxxxx>
> ---
> V1 -> V2:
> - Detect the unhandleable vectoring error in svm_check_emulate_instruction
> instead of handling it in the common MMU code (which is specific for
> cached MMIO)
> V2 -> V3:
> - Use more generic function to check if emulation is allowed when
> vectoring
>
> arch/x86/kvm/svm/svm.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index dd15cc635655..e89c6fc2c4e6 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -4802,6 +4802,12 @@ static int svm_check_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
> bool smep, smap, is_user;
> u64 error_code;
>
> + /* Check that emulation is possible during event vectoring */
> + if ((to_svm(vcpu)->vmcb->control.exit_int_info &
> + SVM_EXITINTINFO_TYPE_MASK) &&
Let this poke out. Alternatively, and probably preferably, capture "svm" locally
and it fits nicely on one line (there's an existing user of to_svm() in this
helper). My objection to a local variable was specifically about a local
"is_event_vectoring", not about local variables in general.
> + !kvm_can_emulate_event_vectoring(emul_type))
> + return X86EMUL_UNHANDLEABLE_VECTORING;
> +
> /* Emulation is always possible when KVM has access to all guest state. */
> if (!sev_guest(vcpu->kvm))
> return X86EMUL_CONTINUE;
> --
> 2.43.0
>