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[79.179.71.128]) by smtp.gmail.com with ESMTPSA id e1sm3816141wrp.49.2020.09.30.08.34.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Sep 2020 08:34:15 -0700 (PDT) Date: Wed, 30 Sep 2020 11:34:12 -0400 From: "Michael S. Tsirkin" To: Stefan Hajnoczi Subject: Re: Outline for VHOST_USER_PROTOCOL_F_VDPA Message-ID: <20200930113129-mutt-send-email-mst@kernel.org> References: <20200928092537.GA44353@stefanha-x1.localdomain> <20200929020114-mutt-send-email-mst@kernel.org> <20200929085751.GA181609@stefanha-x1.localdomain> <20200929055110-mutt-send-email-mst@kernel.org> <20200929183824.GC191675@stefanha-x1.localdomain> <20200930034807-mutt-send-email-mst@kernel.org> <20200930145752.GB320669@stefanha-x1.localdomain> MIME-Version: 1.0 In-Reply-To: <20200930145752.GB320669@stefanha-x1.localdomain> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mst@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/30 00:26:33 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -25 X-Spam_score: -2.6 X-Spam_bar: -- X-Spam_report: (-2.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.469, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: lulu@redhat.com, tiwei.bie@intel.com, jasowang@redhat.com, qemu-devel@nongnu.org, raphael.norwitz@nutanix.com, maxime.coquelin@redhat.com, kraxel@redhat.com, Felipe Franciosi , marcandre.lureau@redhat.com, Nikos Dragazis , changpeng.liu@intel.com, Daniele Buono Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Sep 30, 2020 at 03:57:52PM +0100, Stefan Hajnoczi wrote: > > Architecturally, I think we can have 3 processes: > > > > > > VMM -- guest device emulation -- host backend > > > > > > to me this looks like increasing our defence in depth strength, > > as opposed to just shifting things around ... > > Cool idea. > > Performance will be hard because there is separation between the guest > device emulation and the host backend. Absolutely. As a tradeoff we could put some data path things in the backend, e.g. for virtio it is practical to have control path in emulation layer, data path in the backend. -- MST