Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <20191111172012.28356-1-joao.m.martins@oracle.com> <20191111172012.28356-3-joao.m.martins@oracle.com>
In-Reply-To: <20191111172012.28356-3-joao.m.martins@oracle.com>
From:   Wanpeng Li <kernellwp@gmail.com>
Date:   Tue, 19 Nov 2019 19:36:19 +0800
Message-ID: <CANRm+CyrbiJ068zLRH8ZMttqjnEG38qb1W1SMND+H-D=8N8tVw@mail.gmail.com>
Subject: Re: [PATCH v2 2/3] KVM: VMX: Do not change PID.NDST when loading a
 blocked vCPU
To:     Joao Martins <joao.m.martins@oracle.com>
Cc:     kvm <kvm@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        Liran Alon <liran.alon@oracle.com>,
        Jag Raman <jag.raman@oracle.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Tue, 12 Nov 2019 at 01:23, Joao Martins <joao.m.martins@oracle.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