From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49691) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1f6AhD-0008MH-1k for qemu-devel@nongnu.org; Wed, 11 Apr 2018 04:01:35 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1f6Ah7-00089V-GZ for qemu-devel@nongnu.org; Wed, 11 Apr 2018 04:01:35 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:44476 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 1f6Ah7-00088n-CO for qemu-devel@nongnu.org; Wed, 11 Apr 2018 04:01:29 -0400 References: <20180411072027.5656-1-tiwei.bie@intel.com> From: Jason Wang Message-ID: Date: Wed, 11 Apr 2018 16:01:19 +0800 MIME-Version: 1.0 In-Reply-To: <20180411072027.5656-1-tiwei.bie@intel.com> 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: Tiwei Bie , mst@redhat.com, peterx@redhat.com, qemu-devel@nongnu.org Cc: dan.daly@intel.com, cunming.liang@intel.com, zhihong.wang@intel.com On 2018=E5=B9=B404=E6=9C=8811=E6=97=A5 15:20, 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 > --- > The idea of this patch is to let QEMU push all the IOTLBs > to vhost-user backend without waiting for the queries from > the backend. Because hardware accelerator at the vhost-user > backend may not be able to handle unknown IOVAs. > > This is just a RFC for now. It seems that, it doesn't work > as expected when guest is using kernel driver (To handle > this case, it seems that some RAM regions' events also need > to be listened). Any comments would be appreciated! Thanks! Interesting, a quick question is why this is needed? Can we just use=20 exist IOTLB update message? It looks to me at least kernel does not need this. Thanks