linux-kernel - Re: [PATCH] Add KVM_EXIT_SHUTDOWN metadata for SEV-ES

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Date:   Mon, 21 Mar 2022 12:08:08 -0600
From:   Peter Gonda <pgonda@...gle.com>
To:     Marc Orr <marcorr@...gle.com>
Cc:     kvm list <kvm@...r.kernel.org>, Borislav Petkov <bp@...en8.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        Brijesh Singh <brijesh.singh@....com>,
        Joerg Roedel <jroedel@...e.de>,
        Sean Christopherson <seanjc@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Add KVM_EXIT_SHUTDOWN metadata for SEV-ES

> > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> > index 75fa6dd268f0..5f9d37dd3f6f 100644
> > --- a/arch/x86/kvm/svm/sev.c
> > +++ b/arch/x86/kvm/svm/sev.c
> > @@ -2735,8 +2735,13 @@ static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
> >                 pr_info("SEV-ES guest requested termination: %#llx:%#llx\n",
> >                         reason_set, reason_code);
> >
> > -               ret = -EINVAL;
> > -               break;
> > +               vcpu->run->exit_reason = KVM_EXIT_SHUTDOWN;
> > +               vcpu->run->shutdown.reason = KVM_SHUTDOWN_SEV_TERM;
> > +               vcpu->run->shutdown.ndata = 2;
> > +               vcpu->run->shutdown.data[0] = reason_set;
> > +               vcpu->run->shutdown.data[1] = reason_code;
> > +
> > +               return 0;
>
> Maybe I'm missing something, but don't we want to keep returning an error?
>
> rationale: Current behavior: return -EINVAL to userpsace, but
> userpsace cannot infer where the -EINVAL came from. After this patch:
> We should still return -EINVAL to userspace, but now userspace can
> parse this new info in the KVM run struct to properly terminate.
>

I removed the error return code here since an SEV guest may request a
termination due to no fault of the host at all. This is now inline
with any other shutdown requested by the guest. I don't have a strong
preference here but EINVAL doesn't seem correct in all cases, do
others have any thoughts on this?