Re: [PATCH 1/4 V8] KVM: SEV: Add support for SEV intra host migration

From: Peter Gonda <pgonda@google.com>
To: Joerg Roedel <joro@8bytes.org>
Cc: kvm list <kvm@vger.kernel.org>,
	Sean Christopherson <seanjc@google.com>,
	Marc Orr <marcorr@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	David Rientjes <rientjes@google.com>,
	"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
	Brijesh Singh <brijesh.singh@amd.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/4 V8] KVM: SEV: Add support for SEV intra host migration
Date: Tue, 28 Sep 2021 09:30:08 -0600	[thread overview]
Message-ID: <CAMkAt6q5YbZpnDeFXeQsZcK6WtxdAuMoWqqUwURZ9KLz692MEQ@mail.gmail.com> (raw)
In-Reply-To: <YVMNq4wwjYZ8F7N8@8bytes.org>

On Tue, Sep 28, 2021 at 6:42 AM Joerg Roedel <joro@8bytes.org> wrote:
>
> On Tue, Sep 14, 2021 at 09:47:24AM -0700, Peter Gonda wrote:
> > +static int sev_lock_vcpus_for_migration(struct kvm *kvm)
> > +{
> > +     struct kvm_vcpu *vcpu;
> > +     int i, j;
> > +
> > +     kvm_for_each_vcpu(i, vcpu, kvm) {
> > +             if (mutex_lock_killable(&vcpu->mutex))
> > +                     goto out_unlock;
> > +     }
> > +
> > +     return 0;
> > +
> > +out_unlock:
> > +     kvm_for_each_vcpu(j, vcpu, kvm) {
> > +             mutex_unlock(&vcpu->mutex);
> > +             if (i == j)
> > +                     break;
>
> Hmm, doesn't the mutex_unlock() need to happen after the check?
>

Ah good catch, thanks for the review Joerg! Yes you are right this
results in calling mutex_unlock on a mutex we didn't successfully
lock. I'll fix it in the next version.