From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45448) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dGK9m-0001lV-Dy for qemu-devel@nongnu.org; Thu, 01 Jun 2017 03:04:31 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dGK9i-0003f4-5x for qemu-devel@nongnu.org; Thu, 01 Jun 2017 03:04:30 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47394) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dGK9h-0003ek-WA for qemu-devel@nongnu.org; Thu, 01 Jun 2017 03:04:26 -0400 References: <20170526142858.19931-1-maxime.coquelin@redhat.com> <20170530211819-mutt-send-email-mst@kernel.org> <7d4af4dd-270b-605f-9535-7bf8323e74c2@redhat.com> From: Jason Wang Message-ID: <477d61d4-6654-b1fa-fd86-1876737c886e@redhat.com> Date: Thu, 1 Jun 2017 15:04:10 +0800 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v2 0/6] vhost-user: Specify and implement device IOTLB support List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Maxime Coquelin , "Michael S. Tsirkin" Cc: yuanhan.liu@linux.intel.com, qemu-devel@nongnu.org, peterx@redhat.com, marcandre.lureau@gmail.com, wexu@redhat.com, vkaplans@redhat.com, jfreiman@redhat.com On 2017=E5=B9=B405=E6=9C=8831=E6=97=A5 23:32, Maxime Coquelin wrote: >>>> [0]:https://gitlab.com/mcoquelin/dpdk-next-virtio/commits/vhost_iotl= b_proto_v2=20 >>>> >>>> [1]:https://lists.gnu.org/archive/html/qemu-devel/2016-04/msg00095.h= tml=20 >>>> >>> Overall, this looks good to me. I do think patch 3 isn't a good idea >>> though, if slave wants something let it request it. >>> >>> Need to find out why does vhost in kernel want the used ring iotlb at >>> start time - especially considering we aren't even guaranteed one ent= ry >>> covers the whole ring, and invalidates should affect all addresses at >>> least in theory. >>> >>> >> >> The reason is probably we want to verify whether or not we could=20 >> correctly access used ring in vhost_vq_init_access(). It was there=20 >> since vhost_net is introduced. We can think to remove this limitation=20 >> maybe. > > Even if we remove the limitation on Kernel side, we will still have to > keep this workaround for compatibility with older kernels. Having done=20 > the test, I can confirm it is currently necessary. > > Thanks, > Maxime=20 Right, it was probably too late for the change. Thanks