linux-kernel - Re: [PATCH] KVM: Boost vCPU candidiate in user mode which is delivering interrupt

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:   Mon, 19 Apr 2021 18:59:13 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <kernellwp@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH] KVM: Boost vCPU candidiate in user mode which is
 delivering interrupt

On 19/04/21 18:32, Sean Christopherson wrote:
> If false positives are a big concern, what about adding another pass to the loop
> and only yielding to usermode vCPUs with interrupts in the second full pass?
> I.e. give vCPUs that are already in kernel mode priority, and only yield to
> handle an interrupt if there are no vCPUs in kernel mode.
> 
> kvm_arch_dy_runnable() pulls in pv_unhalted, which seems like a good thing.

pv_unhalted won't help if you're waiting for a kernel spinlock though, 
would it?  Doing two passes (or looking for a "best" candidate that 
prefers kernel mode vCPUs to user mode vCPUs waiting for an interrupt) 
seems like the best choice overall.

Paolo