linux-kernel - Re: The vcpu won't be wakened for a long time

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: Windows password security audit tool. GUI, reports in PDF.

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

Date:   Tue, 14 Dec 2021 17:36:21 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     "Longpeng (Mike, Cloud Infrastructure Service Product Dept.)" 
        <longpeng2@...wei.com>
Cc:     "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "Gonglei (Arei)" <arei.gonglei@...wei.com>,
        Huangzhichao <huangzhichao@...wei.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: The vcpu won't be wakened for a long time

On Tue, Dec 14, 2021, Longpeng (Mike, Cloud Infrastructure Service Product Dept.) wrote:
> Hi guys,
> 
> We find a problem in kvm_vcpu_block().
> 
> The testcase is:
>  - VM configured with 1 vcpu and 1 VF (using vfio-pci passthrough)
>  - the vfio interrupt and the vcpu are bound to the same pcpu
>  - using remapped mode IRTE, NOT posted mode

What exactly is configured to force remapped mode?

> The bug was triggered when the vcpu executed HLT instruction:
> 
> kvm_vcpu_block:
>     prepare_to_rcuwait(&vcpu->wait);
>     for (;;) {
>         set_current_state(TASK_INTERRUPTIBLE);
> 
>         if (kvm_vcpu_check_block(vcpu) < 0)
>             break;
> 					<------------ (*)
>         waited = true;
>         schedule();
>     }
>     finish_rcuwait(&vcpu->wait);
> 
> The vcpu will go to sleep even if an interrupt from the VF is fired at (*) and
> the PIR and ON bit will be set ( in vmx_deliver_posted_interrupt ), so the vcpu
> won't be wakened by subsequent interrupts.
> 
> Any suggestions ? Thanks.

What kernel version?  There have been a variety of fixes/changes in the area in
recent kernels.