From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38424) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1c7eKl-00027y-TQ for qemu-devel@nongnu.org; Fri, 18 Nov 2016 03:15:45 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1c7eKg-0005uW-Ub for qemu-devel@nongnu.org; Fri, 18 Nov 2016 03:15:43 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:47253 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 1c7eKg-0005sW-O2 for qemu-devel@nongnu.org; Fri, 18 Nov 2016 03:15:38 -0500 Received: from pps.filterd (m0098417.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.17/8.16.0.17) with SMTP id uAI8DfBb107832 for ; Fri, 18 Nov 2016 03:15:37 -0500 Received: from e06smtp10.uk.ibm.com (e06smtp10.uk.ibm.com [195.75.94.106]) by mx0a-001b2d01.pphosted.com with ESMTP id 26sqw9y027-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Fri, 18 Nov 2016 03:15:36 -0500 Received: from localhost by e06smtp10.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 18 Nov 2016 08:15:35 -0000 Received: from b06cxnps3075.portsmouth.uk.ibm.com (d06relay10.portsmouth.uk.ibm.com [9.149.109.195]) by d06dlp01.portsmouth.uk.ibm.com (Postfix) with ESMTP id 3FDA417D805D for ; Fri, 18 Nov 2016 08:17:58 +0000 (GMT) Received: from d06av08.portsmouth.uk.ibm.com (d06av08.portsmouth.uk.ibm.com [9.149.37.249]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id uAI8FWiB37486668 for ; Fri, 18 Nov 2016 08:15:32 GMT Received: from d06av08.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av08.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id uAI8FWAI006847 for ; Fri, 18 Nov 2016 01:15:32 -0700 References: <20161116180551.9611-1-pbonzini@redhat.com> <20161116180551.9611-2-pbonzini@redhat.com> From: Christian Borntraeger Date: Fri, 18 Nov 2016 09:15:32 +0100 MIME-Version: 1.0 In-Reply-To: <20161116180551.9611-2-pbonzini@redhat.com> Content-Type: text/plain; charset=iso-8859-15 Content-Transfer-Encoding: 7bit Message-Id: <32da704e-4472-2afa-109f-185575d9f39f@de.ibm.com> Subject: Re: [Qemu-devel] [PATCH 1/3] virtio: introduce grab/release_ioeventfd to fix vhost List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini , qemu-devel@nongnu.org Cc: mst@redhat.com, alex.williamson@redhat.com, felipe@nutanix.com On 11/16/2016 07:05 PM, Paolo Bonzini wrote: > Following the recent refactoring of virtio notifiers [1], more specifically > the patch ed08a2a0b ("virtio: use virtio_bus_set_host_notifier to > start/stop ioeventfd") that uses virtio_bus_set_host_notifier [2] > by default, core virtio code requires 'ioeventfd_started' to be set > to true/false when the host notifiers are configured. > > When vhost is stopped and started, however, there is a stop followed by > another start. Since ioeventfd_started was never set to true, the 'stop' > operation triggered by virtio_bus_set_host_notifier() will not result > in a call to virtio_pci_ioeventfd_assign(assign=false). This leaves > the memory regions with stale notifiers and results on the next start > triggering the following assertion: > > kvm_mem_ioeventfd_add: error adding ioeventfd: File exists > Aborted > > This patch reintroduces (hopefully in a cleaner way) the concept > that was present with ioeventfd_disabled before the refactoring. > When ioeventfd_grabbed>0, ioeventfd_started tracks whether ioeventfd > should be enabled or not, but ioeventfd is actually not started at > all until vhost releases the host notifiers. > > [1] http://lists.nongnu.org/archive/html/qemu-devel/2016-10/msg07748.html > [2] http://lists.nongnu.org/archive/html/qemu-devel/2016-10/msg07760.html > > Reported-by: Felipe Franciosi > Reported-by: Christian Borntraeger > Reported-by: Alex Williamson > Fixes: ed08a2a0b ("virtio: use virtio_bus_set_host_notifier to start/stop ioeventfd") > Signed-off-by: Paolo Bonzini > Message-Id: <20161111192855.26350-1-pbonzini@redhat.com> > Signed-off-by: Paolo Bonzini > --- > v1->v2: more comments [Cornelia] As this seems to fix a functional issues, is there any chance to apply this patch now and not wait for the discussion about patch 2 and 3 to calm down?