From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57205) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1f6G1N-000447-DK for qemu-devel@nongnu.org; Wed, 11 Apr 2018 09:42:49 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1f6G1K-0000aI-8O for qemu-devel@nongnu.org; Wed, 11 Apr 2018 09:42:45 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:37380 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1f6G1K-0000a0-3t for qemu-devel@nongnu.org; Wed, 11 Apr 2018 09:42:42 -0400 References: <20180411072027.5656-1-tiwei.bie@intel.com> <20180411161926-mutt-send-email-mst@kernel.org> From: Jason Wang Message-ID: Date: Wed, 11 Apr 2018 21:42:36 +0800 MIME-Version: 1.0 In-Reply-To: <20180411161926-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [RFC] vhost-user: introduce F_NEED_ALL_IOTLB protocol feature List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" , Tiwei Bie Cc: peterx@redhat.com, qemu-devel@nongnu.org, dan.daly@intel.com, cunming.liang@intel.com, zhihong.wang@intel.com On 2018=E5=B9=B404=E6=9C=8811=E6=97=A5 21:22, Michael S. Tsirkin wrote: > On Wed, Apr 11, 2018 at 03:20:27PM +0800, Tiwei Bie wrote: >> This patch introduces VHOST_USER_PROTOCOL_F_NEED_ALL_IOTLB >> feature for vhost-user. By default, vhost-user backend needs >> to query the IOTLBs from QEMU after meeting unknown IOVAs. >> With this protocol feature negotiated, QEMU will provide all >> the IOTLBs to vhost-user backend without waiting for the >> queries from backend. This is helpful when using a hardware >> accelerator which is not able to handle unknown IOVAs at the >> vhost-user backend. >> >> Signed-off-by: Tiwei Bie > This is potentially a large amount of data to be sent > on a socket. > > I had an impression that a hardware accelerator was using > VFIO anyway. Given this, can't we have QEMU program > the shadow IOMMU tables into VFIO directly? > > So if we want to do this, my understanding is we need to implement the=20 driver inside qemu (or link it to qemu). Thanks