Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: AVIC related warning in enable_irq_window
To:     Maxim Levitsky <mlevitsk@redhat.com>, kvm@vger.kernel.org
Cc:     Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
        linux-kernel@vger.kernel.org
References: <9ce7bb5c4fb8bcc4ac21103f7534a6edfcbe195d.camel@redhat.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <758b27a8-74c0-087d-d90b-d95faee2f561@redhat.com>
Date:   Sat, 2 May 2020 18:42:03 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.6.0
MIME-Version: 1.0
In-Reply-To: <9ce7bb5c4fb8bcc4ac21103f7534a6edfcbe195d.camel@redhat.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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?

svm_set_vintr also has a rather silly

static void svm_set_vintr(struct vcpu_svm *svm)
{
       set_intercept(svm, INTERCEPT_VINTR);
       if (is_intercept(svm, INTERCEPT_VINTR))
               svm_enable_vintr(svm);
}

so I'm thinking of just inlining svm_enable_vintr and renaming
svm_{set,clear}_vintr to svm_{enable,disable}_vintr_window.  Would you
like to send two patches for this, the first to remove the WARN_ON and
the second to do the cleanup?

Thanks,

Paolo

> The code containing this warning was added in commit
> 
> 64b5bd27042639dfcc1534f01771b7b871a02ffe
> KVM: nSVM: ignore L1 interrupt window while running L2 with V_INTR_MASKING=1