Re: [PATCH v2 2/3] KVM: x86: Virtualize AMD CPUID faulting

[Jim Mattson]

On Tue, May 12, 2026 at 2:33 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
> From: Sean Christopherson <seanjc@xxxxxxxxxx>
> Date: Tue, 12 May 2026 14:20:47 -0700
> Subject: [PATCH 1/3] KVM: x86: Consolidate CPUID fault handling for emulator
>  and interception logic
>
> Extract the logic for emulating CPUID faulting (where CPUID #GPs at CPL>0
> outside of SMM) into a dedicated helper and use the helper for both the
> full emulator and the intercepted-CPUID paths.
>
> Opportunistically drop kvm_require_cpl(), as kvm_require_cpl() was the one
> and only user.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---
>  arch/x86/include/asm/kvm_host.h |  1 -
>  arch/x86/kvm/cpuid.c            |  5 +++--
>  arch/x86/kvm/cpuid.h            |  8 ++++++++
>  arch/x86/kvm/emulate.c          |  6 +-----
>  arch/x86/kvm/kvm_emulate.h      |  1 +
>  arch/x86/kvm/x86.c              | 18 ++++++------------
>  6 files changed, 19 insertions(+), 20 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index c470e40a00aa..a9005c61619b 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -2285,7 +2285,6 @@ void kvm_requeue_exception(struct kvm_vcpu *vcpu, unsigned int nr,
>  void kvm_inject_page_fault(struct kvm_vcpu *vcpu, struct x86_exception *fault);
>  void kvm_inject_emulated_page_fault(struct kvm_vcpu *vcpu,
>                                     struct x86_exception *fault);
> -bool kvm_require_cpl(struct kvm_vcpu *vcpu, int required_cpl);
>  bool kvm_require_dr(struct kvm_vcpu *vcpu, int dr);
>
>  static inline int __kvm_irq_line_state(unsigned long *irq_state,
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index e69156b54cff..1c95d1fa3ead 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -2161,9 +2161,10 @@ int kvm_emulate_cpuid(struct kvm_vcpu *vcpu)
>  {
>         u32 eax, ebx, ecx, edx;
>
> -       if (!is_smm(vcpu) && cpuid_fault_enabled(vcpu) &&
> -           !kvm_require_cpl(vcpu, 0))
> +       if (!kvm_is_cpuid_allowed(vcpu)) {
> +               kvm_queue_exception_e(vcpu, GP_VECTOR, 0);
>                 return 1;
> +       }

That's so much better!

Will you drop this in when applying, or should I send a V3?