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[79.176.118.93]) by smtp.gmail.com with ESMTPSA id x7sm13374114wrt.78.2020.10.31.14.49.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 31 Oct 2020 14:49:10 -0700 (PDT) Date: Sat, 31 Oct 2020 17:49:06 -0400 From: "Michael S. Tsirkin" To: Stefan Hajnoczi Subject: Re: Out-of-Process Device Emulation session at KVM Forum 2020 Message-ID: <20201031174726-mutt-send-email-mst@kernel.org> References: <20201029083130.0617a28f@w520.home> <20201029094603.15382476@w520.home> <20201029210407.33d6f008@x1.home> <04179584-3324-994e-d793-04be18d2dab2@redhat.com> MIME-Version: 1.0 In-Reply-To: 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=63.128.21.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/10/31 17:49:15 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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: Elena Ufimtseva , Janosch Frank , John G Johnson , Jason Wang , qemu-devel , Kirti Wankhede , Gerd Hoffmann , Yan Vugenfirer , Jag Raman , Eugenio =?iso-8859-1?Q?P=E9rez?= , Anup Patel , Claudio Imbrenda , Christian Borntraeger , Roman Kagan , Felipe Franciosi , =?iso-8859-1?Q?Marc-Andr=E9?= Lureau , Jens Freimann , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= , Stefano Garzarella , Eduardo Habkost , Sergio Lopez , Kashyap Chamarthy , Darren Kenny , Alex Williamson , Liran Alon , Stefan Hajnoczi , Thanos Makatos , Alex =?iso-8859-1?Q?Benn=E9e?= , David Gibson , Kevin Wolf , Halil Pasic , "Daniel P. Berrange" , Christophe de Dinechin , Paolo Bonzini , fam Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, Oct 30, 2020 at 11:13:59AM +0000, Stefan Hajnoczi wrote: > > > 3. The device can save/load opaque blobs. This is the initial VFIO > > > approach. > > > > > > I still don't get why it must be opaque. > > If the device state format needs to be in the VMM then each device > needs explicit enablement in each VMM (QEMU, cloud-hypervisor, etc). And QEMU cares why exactly? > Let's invert the question: why does the VMM need to understand the > device state of a _passthrough_ device? To support cross version migration and compatibility checks. This problem is harder than it appears, I don't think vendors will do a good job of it without any guidance and standards. -- MST