Re: [PATCH] KVM: SVM: Make sure GHCB is mapped before updating

[Paolo Bonzini]

On 08/04/21 18:04, Tom Lendacky wrote:
> > > > +       if (!err || !sev_es_guest(vcpu->kvm) || !WARN_ON_ONCE(svm->ghcb))
> > > This should be WARN_ON_ONCE(!svm->ghcb), otherwise you'll get the right
> > > result, but get a stack trace immediately.
> > Doh, yep.
> Actually, because of the "or's", this needs to be:
>
> if (!err || !sev_es_guest(vcpu->kvm) || (sev_es_guest(vcpu->kvm) && WARN_ON_ONCE(!svm->ghcb)))

No, || cuts the right-hand side if the left-hand side is true.  So:

- if err == 0, the rest is not evaluated

- if !sev_es_guest(vcpu->kvm), WARN_ON_ONCE(!svm->ghcb) is not evaluated

Paolo