Re: [PATCH v2 10/21] KVM:x86: Add #CP support in guest exception classification

[Yang, Weijiang]

On 4/28/2023 2:09 PM, Binbin Wu wrote:
> On 4/21/2023 9:46 PM, Yang Weijiang wrote:
> > Add handling for Control Protection (#CP) exceptions(vector 21).
> > The new vector is introduced for Intel's Control-Flow Enforcement
> > Technology (CET) relevant violation cases.
> > See Intel's SDM for details.
[...]
> >   -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;
> By definition, #CP is Contributory.
> Can you explain more about this change here which treats #CP as 
> EXCPT_BENIGN when CET is not enabled in guest?

I check the history of this patch, found maintainer modified the patch 
due to some unit test issue in L1. You can check the

details here:

Re: [PATCH v15 04/14] KVM: x86: Add #CP support in guest exception 
dispatch - Sean Christopherson (kernel.org) 
<https://lore.kernel.org/all/YBsZwvwhshw+s7yQ@xxxxxxxxxx/>


> In current KVM code, there is suppose no #CP triggered in guest if CET 
> is not enalbed in guest, right?

Yes.

> >       case DE_VECTOR:
> >       case TS_VECTOR:
> >       case NP_VECTOR:


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