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

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Message-ID: <CAMkAt6q5YbZpnDeFXeQsZcK6WtxdAuMoWqqUwURZ9KLz692MEQ@mail.gmail.com>
Date:   Tue, 28 Sep 2021 09:30:08 -0600
From:   Peter Gonda <pgonda@...gle.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     kvm list <kvm@...r.kernel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Marc Orr <marcorr@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        David Rientjes <rientjes@...gle.com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4 V8] KVM: SEV: Add support for SEV intra host migration

On Tue, Sep 28, 2021 at 6:42 AM Joerg Roedel <joro@...tes.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.