From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59112) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cj3S5-0006v2-4N for qemu-devel@nongnu.org; Wed, 01 Mar 2017 07:33:54 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cj3S1-0003IO-TA for qemu-devel@nongnu.org; Wed, 01 Mar 2017 07:33:53 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:33730 helo=mx0a-001b2d01.pphosted.com) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cj3S1-00032v-Nj for qemu-devel@nongnu.org; Wed, 01 Mar 2017 07:33:49 -0500 Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v21CXAO0028538 for ; Wed, 1 Mar 2017 07:33:13 -0500 Received: from e06smtp12.uk.ibm.com (e06smtp12.uk.ibm.com [195.75.94.108]) by mx0b-001b2d01.pphosted.com with ESMTP id 28wxd7r05r-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Wed, 01 Mar 2017 07:33:10 -0500 Received: from localhost by e06smtp12.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 1 Mar 2017 12:25:30 -0000 From: Halil Pasic Date: Wed, 1 Mar 2017 12:50:04 +0100 Message-Id: <20170301115004.96073-1-pasic@linux.vnet.ibm.com> Subject: [Qemu-devel] [PATCH 1/1] virtio: fallback from irqfd to non-irqfd notify List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org, "Michael S. Tsirkin" Cc: Paolo Bonzini , Stefan Hajnoczi , Cornelia Huck , Halil Pasic The commits 03de2f527 "virtio-blk: do not use vring in dataplane" and 9ffe337c08 "virtio-blk: always use dataplane path if ioeventfd is active" changed how notifications are done for virtio-blk substantially. Due to a race condition interrupts are lost when irqfd is torn down after notify_guest_bh was scheduled but before it actually runs. Furthermore virtio_notify_irqfd ignores the value returned by event_notifier_set which correctly indicates that notification has failed due to bad file descriptor. Let's fix this by making virtio_notify_irqfd fall back to the non-irqfd notification mechanism if event_notifier_set fails. Signed-off-by: Halil Pasic --- This is probably not the only way to fix this: suggestions welcome. I did not use a fixes tag because I'm not sure yet where exactly things got broken. Maybe guys more familiar with dataplane an coroutines can help (Paolo, Stefan). --- hw/virtio/virtio.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 23483c7..8e1c1e9 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -1581,7 +1581,9 @@ void virtio_notify_irqfd(VirtIODevice *vdev, VirtQueue *vq) * to an atomic operation. */ virtio_set_isr(vq->vdev, 0x1); - event_notifier_set(&vq->guest_notifier); + if (event_notifier_set(&vq->guest_notifier)) { + virtio_notify_vector(vdev, vq->vector); + } } static void virtio_irq(VirtQueue *vq) -- 2.8.4