From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46107) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eevAp-0006MO-5x for qemu-devel@nongnu.org; Thu, 25 Jan 2018 22:59:32 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eevAm-0006U9-4k for qemu-devel@nongnu.org; Thu, 25 Jan 2018 22:59:31 -0500 Received: from mx1.redhat.com ([209.132.183.28]:59514) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eevAm-0006Te-0S for qemu-devel@nongnu.org; Thu, 25 Jan 2018 22:59:28 -0500 References: <20180125040328.22867-1-tiwei.bie@intel.com> <20180125040328.22867-7-tiwei.bie@intel.com> <20180126015553-mutt-send-email-mst@kernel.org> From: Jason Wang Message-ID: <28ab37d5-6cf6-866d-9167-e14e7441415f@redhat.com> Date: Fri, 26 Jan 2018 11:41:27 +0800 MIME-Version: 1.0 In-Reply-To: <20180126015553-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] [virtio-dev] Re: [PATCH v1 6/6] vhost-user: add VFIO based accelerators support List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" , Tiwei Bie Cc: qemu-devel@nongnu.org, virtio-dev@lists.oasis-open.org, alex.williamson@redhat.com, pbonzini@redhat.com, stefanha@redhat.com, cunming.liang@intel.com, dan.daly@intel.com, jianfeng.tan@intel.com, zhihong.wang@intel.com, xiao.w.wang@intel.com On 2018=E5=B9=B401=E6=9C=8826=E6=97=A5 07:59, Michael S. Tsirkin wrote: >> The virtual IOMMU isn't supported by the accelerators for now. >> Because vhost-user currently lacks of an efficient way to share >> the IOMMU table in VM to vhost backend. That's why the software >> implementation of virtual IOMMU support in vhost-user backend >> can't support dynamic mapping well. > What exactly is meant by that? vIOMMU seems to work for people, > it's not that fast if you change mappings all the time, > but e.g. dpdk within guest doesn't. Yes, software implementation support dynamic mapping for sure. I think=20 the point is, current vhost-user backend can not program hardware IOMMU.=20 So it can not let hardware accelerator to cowork with software vIOMMU. I=20 think that's another call to implement the offloaded path inside qemu=20 which has complete support for vIOMMU co-operated VFIO. Thanks > >> Once this problem is solved >> in vhost-user, virtual IOMMU can be supported by accelerators >> too, and the IOMMU feature bit checking in this patch can be >> removed. > Given it works with software backends right now, I suspect > this will be up to you guys to address. > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: virtio-dev-return-3077-cohuck=redhat.com@lists.oasis-open.org Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [66.179.20.138]) by lists.oasis-open.org (Postfix) with ESMTP id B4D9258191C4 for ; Thu, 25 Jan 2018 19:41:55 -0800 (PST) References: <20180125040328.22867-1-tiwei.bie@intel.com> <20180125040328.22867-7-tiwei.bie@intel.com> <20180126015553-mutt-send-email-mst@kernel.org> From: Jason Wang Message-ID: <28ab37d5-6cf6-866d-9167-e14e7441415f@redhat.com> Date: Fri, 26 Jan 2018 11:41:27 +0800 MIME-Version: 1.0 In-Reply-To: <20180126015553-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset="utf-8"; format="flowed" Content-Transfer-Encoding: 8bit Content-Language: en-US Subject: Re: [virtio-dev] Re: [PATCH v1 6/6] vhost-user: add VFIO based accelerators support To: "Michael S. Tsirkin" , Tiwei Bie Cc: qemu-devel@nongnu.org, virtio-dev@lists.oasis-open.org, alex.williamson@redhat.com, pbonzini@redhat.com, stefanha@redhat.com, cunming.liang@intel.com, dan.daly@intel.com, jianfeng.tan@intel.com, zhihong.wang@intel.com, xiao.w.wang@intel.com List-ID: On 2018年01月26日 07:59, Michael S. Tsirkin wrote: >> The virtual IOMMU isn't supported by the accelerators for now. >> Because vhost-user currently lacks of an efficient way to share >> the IOMMU table in VM to vhost backend. That's why the software >> implementation of virtual IOMMU support in vhost-user backend >> can't support dynamic mapping well. > What exactly is meant by that? vIOMMU seems to work for people, > it's not that fast if you change mappings all the time, > but e.g. dpdk within guest doesn't. Yes, software implementation support dynamic mapping for sure. I think the point is, current vhost-user backend can not program hardware IOMMU. So it can not let hardware accelerator to cowork with software vIOMMU. I think that's another call to implement the offloaded path inside qemu which has complete support for vIOMMU co-operated VFIO. Thanks > >> Once this problem is solved >> in vhost-user, virtual IOMMU can be supported by accelerators >> too, and the IOMMU feature bit checking in this patch can be >> removed. > Given it works with software backends right now, I suspect > this will be up to you guys to address. > --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org