From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by dpdk.org (Postfix) with ESMTP id A82021396; Thu, 3 Nov 2016 21:36:57 +0100 (CET) Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 922AF4E33D; Thu, 3 Nov 2016 20:36:56 +0000 (UTC) Received: from [10.36.6.90] (vpn1-6-90.ams2.redhat.com [10.36.6.90]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id uA3KaqxO024111 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Thu, 3 Nov 2016 16:36:55 -0400 To: Yuanhan Liu , dev@dpdk.org References: <1478189400-14606-1-git-send-email-yuanhan.liu@linux.intel.com> <1478189400-14606-2-git-send-email-yuanhan.liu@linux.intel.com> From: Maxime Coquelin Message-ID: <915489cd-7e1a-9a0c-ab9d-780f6103501b@redhat.com> Date: Thu, 3 Nov 2016 21:36:52 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <1478189400-14606-2-git-send-email-yuanhan.liu@linux.intel.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.68 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Thu, 03 Nov 2016 20:36:56 +0000 (UTC) Cc: Ilya Maximets , stable@dpdk.org Subject: Re: [dpdk-dev] [PATCH 1/8] net/virtio: revert "virtio: fix restart" X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 03 Nov 2016 20:36:57 -0000 Hi Yuanhan, On 11/03/2016 05:09 PM, Yuanhan Liu wrote: > This reverts commit 9a0615af7746 ("virtio: fix restart"); conflict is > manually addressed. > > Kyle reported an issue with above commit > > qemu-kvm: Guest moved used index from 5 to 1 > > with following steps, > > 1) Start my virtio interfaces > 2) Send some traffic into/out of the interfaces > 3) Stop the interfaces > 4) Start the interfaces > 5) Send some more traffic > > And here are some quotes from Kyle's analysis, > > Prior to the patch, if an interface were stopped then started, without > restarting the application, the queues would be left as-is, because > hw->started would be set to 1. Now, calling stop sets hw->started to 0, > which means the next call to start will "touch the queues". This is the > unintended side-effect that causes the problem. Maybe a good idea to explain what is the problem the revert aims to fix. It does not seem to be clearly stated in the commit message. > > Fixes: 9a0615af7746 ("virtio: fix restart") > > Cc: Jianfeng Tan > Cc: > Reported-by: Kyle Larose > Signed-off-by: Yuanhan Liu Thanks, Maxime