From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
srutherford@google.com, joro@8bytes.org, brijesh.singh@amd.com,
thomas.lendacky@amd.com, venu.busireddy@oracle.com,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Borislav Petkov <bp@suse.de>,
x86@kernel.org, Ashish Kalra <ashish.kalra@amd.com>
Subject: Re: [PATCH 0/3] KVM: x86: guest interface for SEV live migration
Date: Tue, 20 Apr 2021 22:49:51 +0000 [thread overview]
Message-ID: <YH9aj8FLQ4z4Po/x@google.com> (raw)
In-Reply-To: <4b96c4fc-23a4-0bd2-ea58-fa6d81e50b15@redhat.com>
On Tue, Apr 20, 2021, Paolo Bonzini wrote:
> On 20/04/21 22:16, Sean Christopherson wrote:
> > On Tue, Apr 20, 2021, Sean Christopherson wrote:
> > > On Tue, Apr 20, 2021, Paolo Bonzini wrote:
> > > > In this particular case, if userspace sets the bit in CPUID2 but doesn't
> > > > handle KVM_EXIT_HYPERCALL, the guest will probably trigger some kind of
> > > > assertion failure as soon as it invokes the HC_PAGE_ENC_STATUS hypercall.
> >
> > Oh! Almost forgot my hail mary idea. Instead of a new capability, can we
> > reject the hypercall if userspace has _not_ set KVM_CAP_ENFORCE_PV_FEATURE_CPUID?
> >
> > if (vcpu->arch.pv_cpuid.enforce &&
> > !guest_pv_has(vcpu, KVM_FEATURE_HC_PAGE_ENC_STATUS)
> > break;
>
> Couldn't userspace enable that capability and _still_ copy the supported
> CPUID blindly to the guest CPUID, without supporting the hypercall?
Yes. I was going to argue that we get to define the behavior, but that's not
true because it would break existing VMMs that blindly copy. Capability it is...
next prev parent reply other threads:[~2021-04-20 22:50 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-20 11:20 [PATCH 0/3] KVM: x86: guest interface for SEV live migration Paolo Bonzini
2021-04-20 15:15 ` Sean Christopherson
2021-04-20 18:27 ` Paolo Bonzini
2021-04-20 17:31 ` Sean Christopherson
2021-04-20 18:11 ` Ashish Kalra
2021-04-20 18:40 ` Sean Christopherson
2021-04-20 18:58 ` Sean Christopherson
2021-04-20 18:39 ` Paolo Bonzini
2021-04-20 19:02 ` Sean Christopherson
2021-04-20 20:16 ` Sean Christopherson
2021-04-20 20:58 ` Paolo Bonzini
2021-04-20 22:49 ` Sean Christopherson [this message]
2021-04-20 23:20 ` Sean Christopherson
2021-04-21 12:03 ` Paolo Bonzini
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