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Tsirkin" To: Thomas Huth Cc: Peter Xu , Yuri Benditovich , eduardo@habkost.net, marcel.apfelbaum@gmail.com, philmd@linaro.org, wangyanan55@huawei.com, dmitry.fleytman@gmail.com, akihiko.odaki@daynix.com, jasowang@redhat.com, sriram.yagnaraman@est.tech, sw@weilnetz.de, qemu-devel@nongnu.org, yan@daynix.com, Fabiano Rosas , Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , devel@lists.libvirt.org Subject: Re: [PATCH v2 4/4] virtio-net: Add support for USO features Message-ID: <20240726032520-mutt-send-email-mst@kernel.org> References: <20230731223148.1002258-1-yuri.benditovich@daynix.com> <20230731223148.1002258-5-yuri.benditovich@daynix.com> <20240726020656-mutt-send-email-mst@kernel.org> <775ff713-f7d3-4fdc-8ba0-4ebde577040d@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <775ff713-f7d3-4fdc-8ba0-4ebde577040d@redhat.com> Received-SPF: pass client-ip=170.10.129.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.144, 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_H3=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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Fri, Jul 26, 2024 at 09:03:24AM +0200, Thomas Huth wrote: > On 26/07/2024 08.08, Michael S. Tsirkin wrote: > > On Thu, Jul 25, 2024 at 06:18:20PM -0400, Peter Xu wrote: > > > On Tue, Aug 01, 2023 at 01:31:48AM +0300, Yuri Benditovich wrote: > > > > USO features of virtio-net device depend on kernel ability > > > > to support them, for backward compatibility by default the > > > > features are disabled on 8.0 and earlier. > > > > > > > > Signed-off-by: Yuri Benditovich > > > > Signed-off-by: Andrew Melnychecnko > > > > > > Looks like this patch broke migration when the VM starts on a host that has > > > USO supported, to another host that doesn't.. > > > > This was always the case with all offloads. The answer at the moment is, > > don't do this. > > May I ask for my understanding: > "don't do this" = don't automatically enable/disable virtio features in QEMU > depending on host kernel features, or "don't do this" = don't try to migrate > between machines that have different host kernel features? The later. > > Long term, we need to start exposing management APIs > > to discover this, and management has to disable unsupported features. > > Ack, this likely needs some treatments from the libvirt side, too. > > Thomas