linux-kernel - Re: [PATCH RESEND] KVM: Boosting vCPUs that are delivering interrupts

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]

Message-ID: <CANRm+Cw43DKqD17U+7-OPX3BmeNBThSe9-uWP2Atob+A0ApzLA@mail.gmail.com>
Date:   Thu, 18 Jul 2019 16:43:28 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Christian Borntraeger <borntraeger@...ibm.com>,
        LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Radim Krčmář <rkrcmar@...hat.com>
Subject: Re: [PATCH RESEND] KVM: Boosting vCPUs that are delivering interrupts

On Thu, 18 Jul 2019 at 16:34, Paolo Bonzini <pbonzini@...hat.com> wrote:
>
> On 18/07/19 10:15, Christian Borntraeger wrote:
> >
> >
> > On 18.07.19 09:59, Paolo Bonzini wrote:
> >> On 12/07/19 09:15, Wanpeng Li wrote:
> >>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> >>> index b4ab59d..2c46705 100644
> >>> --- a/virt/kvm/kvm_main.c
> >>> +++ b/virt/kvm/kvm_main.c
> >>> @@ -2404,8 +2404,10 @@ void kvm_vcpu_kick(struct kvm_vcpu *vcpu)
> >>>     int me;
> >>>     int cpu = vcpu->cpu;
> >>>
> >>> -   if (kvm_vcpu_wake_up(vcpu))
> >>> +   if (kvm_vcpu_wake_up(vcpu)) {
> >>> +           vcpu->preempted = true;
> >>>             return;
> >>> +   }
> >>>
> >>>     me = get_cpu();
> >>>     if (cpu != me && (unsigned)cpu < nr_cpu_ids && cpu_online(cpu))
> >>>
> >>
> >> Who is resetting vcpu->preempted to false in this case?  This also
> >> applies to s390 in fact.
> >
> > Isnt that done by the sched_in handler?
>
> I am a bit confused because, if it is done by the sched_in later, I
> don't understand why the sched_out handler hasn't set vcpu->preempted
> already.
>
> The s390 commit message is not very clear, but it talks about "a former
> sleeping cpu" that "gave up the cpu voluntarily".  Does "voluntarily"
> that mean it is in kvm_vcpu_block?  But then at least for x86 it would

see the prepare_to_swait_exlusive() in kvm_vcpu_block(), the task will
be set in TASK_INTERRUPTIBLE state, kvm_sched_out will set
vcpu->preempted to true iff current->state == TASK_RUNNING.

Regards,
Wanpeng Li