Re: [PATCH v15 04/14] KVM: x86: Add #CP support in guest exception dispatch

[Paolo Bonzini]

On 03/02/21 22:46, Sean Christopherson wrote:
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index dbca1687ae8e..0b6dab6915a3 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -2811,7 +2811,7 @@ static int nested_check_vm_entry_controls(struct kvm_vcpu *vcpu,
>                 /* VM-entry interruption-info field: deliver error code */
>                 should_have_error_code =
>                         intr_type == INTR_TYPE_HARD_EXCEPTION && prot_mode &&
> -                       x86_exception_has_error_code(vector);
> +                       x86_exception_has_error_code(vcpu, vector);
>                 if (CC(has_error_code != should_have_error_code))
>                         return -EINVAL;
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 28fea7ff7a86..0288d6a364bd 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -437,17 +437,20 @@ EXPORT_SYMBOL_GPL(kvm_spurious_fault);
>  #define EXCPT_CONTRIBUTORY     1
>  #define EXCPT_PF               2
>
> -static int exception_class(int vector)
> +static int exception_class(struct kvm_vcpu *vcpu, int vector)
>  {
>         switch (vector) {
>         case PF_VECTOR:
>                 return EXCPT_PF;
> +       case CP_VECTOR:
> +               if (vcpu->arch.cr4_guest_rsvd_bits & X86_CR4_CET)
> +                       return EXCPT_BENIGN;
> +               return EXCPT_CONTRIBUTORY;
>         case DE_VECTOR:
>         case TS_VECTOR:
>         case NP_VECTOR:
>         case SS_VECTOR:
>         case GP_VECTOR:
> -       case CP_VECTOR:
>                 return EXCPT_CONTRIBUTORY;
>         default:
>                 break;
> @@ -588,8 +591,8 @@ static void kvm_multiple_exception(struct kvm_vcpu *vcpu,
>                 kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
>                 return;
>         }
> -       class1 = exception_class(prev_nr);
> -       class2 = exception_class(nr);
> +       class1 = exception_class(vcpu, prev_nr);
> +       class2 = exception_class(vcpu, nr);
>         if ((class1 == EXCPT_CONTRIBUTORY && class2 == EXCPT_CONTRIBUTORY)
>                 || (class1 == EXCPT_PF && class2 != EXCPT_BENIGN)) {
>                 /*
> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
> index a14da36a30ed..dce756ffb577 100644
> --- a/arch/x86/kvm/x86.h
> +++ b/arch/x86/kvm/x86.h
> @@ -120,12 +120,16 @@ static inline bool is_la57_mode(struct kvm_vcpu *vcpu)
>  #endif
>  }
>
> -static inline bool x86_exception_has_error_code(unsigned int vector)
> +static inline bool x86_exception_has_error_code(struct kvm_vcpu *vcpu,
> +                                               unsigned int vector)
>  {
>         static u32 exception_has_error_code = BIT(DF_VECTOR) | BIT(TS_VECTOR) |
>                         BIT(NP_VECTOR) | BIT(SS_VECTOR) | BIT(GP_VECTOR) |
>                         BIT(PF_VECTOR) | BIT(AC_VECTOR) | BIT(CP_VECTOR);
>
> +       if (vector == CP_VECTOR && (vcpu->arch.cr4_guest_rsvd_bits & X86_CR4_CET))
> +               return false;
> +
>         return (1U << vector) & exception_has_error_code;
>  }

Squashed, thanks.  I made a small change to the last hunk:

        if (!((1U << vector) & exception_has_error_code))
                return false;

        if (vector == CP_VECTOR)
                return !(vcpu->arch.cr4_guest_rsvd_bits & X86_CR4_CET);

        return true;