linux-kernel - Re: [RFC PATCH 0/2] Mitigating Excessive Pause-Loop Exiting in VM-Agnostic KVM

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-next>] [day] [month] [year] [list]

Date:   Mon, 26 Apr 2021 11:02:19 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Kenta Ishiguro <kentaishiguro@...ab.ics.keio.ac.jp>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        David Hildenbrand <david@...hat.com>,
        kvm <kvm@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        Pierre-Louis Aublin <pl@...ab.ics.keio.ac.jp>,
        河野健二 <kono@...ab.ics.keio.ac.jp>
Subject: Re: [RFC PATCH 0/2] Mitigating Excessive Pause-Loop Exiting in
 VM-Agnostic KVM

On Mon, 26 Apr 2021 at 10:56, Kenta Ishiguro
<kentaishiguro@...ab.ics.keio.ac.jp> wrote:
>
> Dear all,
>
> Thank you for the insightful feedback.
>
> Does Sean's suggested version of Wanpeng's patch mark a running vCPU as an IPI
> receiver? If it's right, I think the candidate set of vCPUs for boost is
> slightly different between using kvm_arch_interrupt_delivery and using boolean
> ipi_received. In the version of using boolean ipi_received, vCPUs which
> receive IPI while running are also candidates for a boost.
> However, they likely have already responded to their IPI before they exit.

             if (READ_ONCE(vcpu->preempted) && yield_to_kernel_mode &&
+                !READ_ONCE(vcpu->ipi_received) &&

There is a vcpu->preempted checking here.

    Wanpeng