From: Maxim Levitsky <mlevitsk@redhat.com>
To: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
Paolo Bonzini <pbonzini@redhat.com>,
kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Subject: Re: AVIC related warning in enable_irq_window
Date: Mon, 04 May 2020 12:13:47 +0300 [thread overview]
Message-ID: <159382e7fdf0f9b50d79e29554842289e92e1ed7.camel@redhat.com> (raw)
In-Reply-To: <c5c32371-4b4e-1382-c616-3830ba46bf85@amd.com>
On Mon, 2020-05-04 at 15:46 +0700, Suravee Suthikulpanit wrote:
> Paolo / Maxim,
>
> On 5/2/20 11:42 PM, Paolo Bonzini wrote:
> > On 02/05/20 15:58, Maxim Levitsky wrote:
> > > The AVIC is disabled by svm_toggle_avic_for_irq_window, which calls
> > > kvm_request_apicv_update, which broadcasts the KVM_REQ_APICV_UPDATE vcpu request,
> > > however it doesn't broadcast it to CPU on which now we are running, which seems OK,
> > > because the code that handles that broadcast runs on each VCPU entry, thus
> > > when this CPU will enter guest mode it will notice and disable the AVIC.
> > >
> > > However later in svm_enable_vintr, there is test 'WARN_ON(kvm_vcpu_apicv_active(&svm->vcpu));'
> > > which is still true on current CPU because of the above.
> >
> > Good point! We can just remove the WARN_ON I think. Can you send a patch?
>
> Instead, as an alternative to remove the WARN_ON(), would it be better to just explicitly
> calling kvm_vcpu_update_apicv(vcpu) to update the apicv_active flag right after
> kvm_request_apicv_update()?
>
> Thanks,
> Suravee
>
This should work IMHO, other that the fact kvm_vcpu_update_apicv will be called again,
when this vcpu is entered since the KVM_REQ_APICV_UPDATE will still be pending on it.
It shoudn't be a problem, and we can even add a check to do nothing when it is called
while avic is already in target enable state.
Best regards,
Maxim Levitsky
next prev parent reply other threads:[~2020-05-04 9:13 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-02 13:58 AVIC related warning in enable_irq_window Maxim Levitsky
2020-05-02 16:42 ` Paolo Bonzini
2020-05-02 16:43 ` Maxim Levitsky
2020-05-03 19:18 ` Suravee Suthikulpanit
2020-05-04 8:46 ` Suravee Suthikulpanit
2020-05-04 9:13 ` Maxim Levitsky [this message]
2020-05-04 9:25 ` Paolo Bonzini
2020-05-04 10:37 ` Suravee Suthikulpanit
2020-05-04 10:49 ` Paolo Bonzini
2020-05-05 7:55 ` Suravee Suthikulpanit
2020-05-05 11:40 ` Maxim Levitsky
2020-05-05 12:12 ` Paolo Bonzini
2020-05-06 0:42 ` Suravee Suthikulpanit
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