From: Sean Christopherson <seanjc@google.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] KVM: x86: Identify vCPU0 by its vcpu_idx instead of walking vCPUs array
Date: Mon, 20 Sep 2021 14:57:15 +0000 [thread overview]
Message-ID: <YUihS9CcTh9m53J6@google.com> (raw)
In-Reply-To: <87czpd2bsi.fsf@vitty.brq.redhat.com>
On Mon, Sep 13, 2021, Vitaly Kuznetsov wrote:
> Sean Christopherson <seanjc@google.com> writes:
>
> > Use vcpu_idx to identify vCPU0 when updating HyperV's TSC page, which is
> > shared by all vCPUs and "owned" by vCPU0 (because vCPU0 is the only vCPU
> > that's guaranteed to exist). Using kvm_get_vcpu() to find vCPU works,
> > but it's a rather odd and suboptimal method to check the index of a given
> > vCPU.
> >
> > No functional change intended.
> >
> > Signed-off-by: Sean Christopherson <seanjc@google.com>
> > ---
> > arch/x86/kvm/x86.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 86539c1686fa..6ab851df08d1 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -2969,7 +2969,7 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
> > offsetof(struct compat_vcpu_info, time));
> > if (vcpu->xen.vcpu_time_info_set)
> > kvm_setup_pvclock_page(v, &vcpu->xen.vcpu_time_info_cache, 0);
> > - if (v == kvm_get_vcpu(v->kvm, 0))
> > + if (!v->vcpu_idx)
> > kvm_hv_setup_tsc_page(v->kvm, &vcpu->hv_clock);
> > return 0;
> > }
>
> " ... instead of walking vCPUs array" in the Subject line is a bit
> confusing because kvm_get_vcpu() doesn't actually walk anything, it just
> returns 'kvm->vcpus[i]' after checking that we actually have that many
> vCPUs. The patch itself is OK, so
Argh, yes, I have a feeling I wrote the changelog after digging into the history
of kvm_get_vcpu().
Paolo, can you tweak the shortlog to:
KVM: x86: Identify vCPU0 by its vcpu_idx instead of its vCPUs array entry
next prev parent reply other threads:[~2021-09-20 14:57 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-10 18:32 [PATCH 0/2] KVM: x86: vcpu_idx related cleanups Sean Christopherson
2021-09-10 18:32 ` [PATCH 1/2] KVM: x86: Query vcpu->vcpu_idx directly and drop its accessor Sean Christopherson
2021-09-12 10:49 ` Maxim Levitsky
2021-09-13 7:02 ` Vitaly Kuznetsov
2021-09-10 18:32 ` [PATCH 2/2] KVM: x86: Identify vCPU0 by its vcpu_idx instead of walking vCPUs array Sean Christopherson
2021-09-10 21:46 ` Jim Mattson
2021-09-12 10:52 ` Maxim Levitsky
2021-09-13 7:07 ` Vitaly Kuznetsov
2021-09-20 14:57 ` Sean Christopherson [this message]
2021-09-22 7:41 ` Paolo Bonzini
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