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

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Date:   Thu, 4 Feb 2021 08:42:23 -0800
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Yang Weijiang <weijiang.yang@...el.com>, jmattson@...gle.com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        yu.c.zhang@...ux.intel.com
Subject: Re: [PATCH v15 04/14] KVM: x86: Add #CP support in guest exception
 dispatch

On Thu, Feb 04, 2021, Paolo Bonzini wrote:
> 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:

This removal got lost when squasing.

arch/x86/kvm/x86.c: In function ‘exception_class’:
arch/x86/kvm/x86.c:455:2: error: duplicate case value
  455 |  case CP_VECTOR:
      |  ^~~~
arch/x86/kvm/x86.c:446:2: note: previously used here
  446 |  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;

Ha, I guessed wrong, that was my first pass at it :-)