From: Paolo Bonzini <pbonzini@redhat.com>
To: asmetanin@virtuozzo.com, kvm@vger.kernel.org
Cc: Gleb Natapov <gleb@kernel.org>,
Roman Kagan <rkagan@virtuozzo.com>,
"Denis V. Lunev" <den@openvz.org>,
qemu-devel@nongnu.org
Subject: Re: [PATCH v1] kvm/x86: Remove Hyper-V SynIC timer stopping
Date: Wed, 16 Dec 2015 18:54:05 +0100 [thread overview]
Message-ID: <5671A53D.2070501@redhat.com> (raw)
In-Reply-To: <566EF5E3.7060000@virtuozzo.com>
On 14/12/2015 18:01, Andrey Smetanin wrote:
> host guest
> start periodic stimer
> start periodic timer
> timer expires after 15ms
> send expiration message into guest
> restart periodic timer
> ....doing something....
> timer expires again after 15 ms
> msg slot is still not cleared so
> setup ->msg_pending
> restart periodic timer
> ....doing something....
> process timer msg and clear slot
> so ->msg_pending was set:
> send EOM into host
> received EOM
> queued call of kvm_hv_process_stimers()
> by KVM_REQ_HV_STIMER
>
> kvm_hv_process_stimers():
> ...
> stimer_stop()
> if (time_now >= stimer->exp_time)
> stimer_expiration(stimer);
> But time_now < stimer->exp_time, so stimer_expiration is not called
> in this case and timer is not restarted. so guest lose timer.
Great, this explains it.
Paolo
WARNING: multiple messages have this Message-ID (diff)
From: Paolo Bonzini <pbonzini@redhat.com>
To: asmetanin@virtuozzo.com, kvm@vger.kernel.org
Cc: Gleb Natapov <gleb@kernel.org>, "Denis V. Lunev" <den@openvz.org>,
Roman Kagan <rkagan@virtuozzo.com>,
qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH v1] kvm/x86: Remove Hyper-V SynIC timer stopping
Date: Wed, 16 Dec 2015 18:54:05 +0100 [thread overview]
Message-ID: <5671A53D.2070501@redhat.com> (raw)
In-Reply-To: <566EF5E3.7060000@virtuozzo.com>
On 14/12/2015 18:01, Andrey Smetanin wrote:
> host guest
> start periodic stimer
> start periodic timer
> timer expires after 15ms
> send expiration message into guest
> restart periodic timer
> ....doing something....
> timer expires again after 15 ms
> msg slot is still not cleared so
> setup ->msg_pending
> restart periodic timer
> ....doing something....
> process timer msg and clear slot
> so ->msg_pending was set:
> send EOM into host
> received EOM
> queued call of kvm_hv_process_stimers()
> by KVM_REQ_HV_STIMER
>
> kvm_hv_process_stimers():
> ...
> stimer_stop()
> if (time_now >= stimer->exp_time)
> stimer_expiration(stimer);
> But time_now < stimer->exp_time, so stimer_expiration is not called
> in this case and timer is not restarted. so guest lose timer.
Great, this explains it.
Paolo
next prev parent reply other threads:[~2015-12-16 17:54 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-14 15:33 [PATCH v1] kvm/x86: Remove Hyper-V SynIC timer stopping Andrey Smetanin
2015-12-14 15:33 ` [Qemu-devel] " Andrey Smetanin
2015-12-14 16:09 ` Paolo Bonzini
2015-12-14 16:09 ` [Qemu-devel] " Paolo Bonzini
2015-12-14 16:48 ` Andrey Smetanin
2015-12-14 16:48 ` [Qemu-devel] " Andrey Smetanin
2015-12-14 17:01 ` Andrey Smetanin
2015-12-14 17:01 ` [Qemu-devel] " Andrey Smetanin
2015-12-16 17:54 ` Paolo Bonzini [this message]
2015-12-16 17:54 ` Paolo Bonzini
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