linux-kernel - Re: AVIC related warning in enable_irq

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <758b27a8-74c0-087d-d90b-d95faee2f561@redhat.com>
Date:   Sat, 2 May 2020 18:42:03 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>, kvm@...r.kernel.org
Cc:     Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: AVIC related warning in enable_irq_window

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