linux-kernel - Re: [PATCH v2 2/3] KVM: VMX: Do not change PID.NDST when loading a blocked vCPU

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Message-ID: <CANRm+CyrbiJ068zLRH8ZMttqjnEG38qb1W1SMND+H-D=8N8tVw@mail.gmail.com>
Date:   Tue, 19 Nov 2019 19:36:19 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Joao Martins <joao.m.martins@...cle.com>
Cc:     kvm <kvm@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Liran Alon <liran.alon@...cle.com>,
        Jag Raman <jag.raman@...cle.com>
Subject: Re: [PATCH v2 2/3] KVM: VMX: Do not change PID.NDST when loading a
 blocked vCPU

On Tue, 12 Nov 2019 at 01:23, Joao Martins <joao.m.martins@...cle.com> wrote:
>
> While vCPU is blocked (in kvm_vcpu_block()), it may be preempted which
> will cause vmx_vcpu_pi_put() to set PID.SN.  If later the vCPU will be

How can this happen? 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.

    Wanpeng