From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by dpdk.org (Postfix) with ESMTP id 4AB381DB1 for ; Thu, 2 Jul 2015 02:29:46 +0200 (CEST) Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga102.fm.intel.com with ESMTP; 01 Jul 2015 17:29:41 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.15,389,1432623600"; d="scan'208";a="517504349" Received: from pgsmsx108.gar.corp.intel.com ([10.221.44.103]) by FMSMGA003.fm.intel.com with ESMTP; 01 Jul 2015 17:29:40 -0700 Received: from shsmsx101.ccr.corp.intel.com (10.239.4.153) by PGSMSX108.gar.corp.intel.com (10.221.44.103) with Microsoft SMTP Server (TLS) id 14.3.224.2; Thu, 2 Jul 2015 08:29:39 +0800 Received: from shsmsx102.ccr.corp.intel.com ([169.254.2.165]) by SHSMSX101.ccr.corp.intel.com ([169.254.1.246]) with mapi id 14.03.0224.002; Thu, 2 Jul 2015 08:29:38 +0800 From: "Ouyang, Changchun" To: "Xie, Huawei" , "dev@dpdk.org" , Thomas Monjalon Thread-Topic: [dpdk-dev] [PATCH] virtio: fix the vq size issue Thread-Index: AQHQs9JlQEOaxBUIeEyxKL7zRjwCJJ3HUlRQ Date: Thu, 2 Jul 2015 00:29:37 +0000 Message-ID: References: <1435736930-26737-1-git-send-email-changchun.ouyang@intel.com> In-Reply-To: Accept-Language: zh-CN, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.239.127.40] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Subject: Re: [dpdk-dev] [PATCH] virtio: fix the vq size issue 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, 02 Jul 2015 00:29:46 -0000 Hi huawei, > -----Original Message----- > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Xie, Huawei > Sent: Wednesday, July 1, 2015 11:53 PM > To: dev@dpdk.org; Thomas Monjalon > Subject: Re: [dpdk-dev] [PATCH] virtio: fix the vq size issue >=20 > On 7/1/2015 3:49 PM, Ouyang Changchun wrote: > > This commit breaks virtio basic packets rx functionality: > > d78deadae4dca240e85054bf2d604a801676becc > > > > The QEMU use 256 as default vring size, also use this default value to > > calculate the virtio avail ring base address and used ring base > > address, and vhost in the backend use the ring base address to do packe= t > IO. > > > > Virtio spec also says the queue size in PCI configuration is > > read-only, so virtio front end can't change it. just need use the > > read-only value to allocate space for vring and calculate the avail > > and used ring base address. Otherwise, the avail and used ring base > address will be different between host and guest, accordingly, packet IO > can't work normally. > virtio driver could still use the vq_size to initialize avail ring and us= e ring so > that they still have the same base address. > The other issue is vhost use index & (vq->size -1) to index the ring. I am not sure what is your clear message here, Vhost has no choice but use vq->size -1 to index the ring,=20 It is qemu that always use 256 as the vq size, and set the avail and used r= ing base address, It also tells vhost the vq size is 256. >=20 >=20 > Thomas: > This fix works but introduces slight change with original code. Could we = just > rollback that commit? What's your major concern for the slight change here? just removing the unnecessary check for nb_desc itself. So I think no issue for the slight change. =20 Thanks Changchun