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Tsirkin" Cc: Jason Wang , Yuri Benditovich , qemu-devel@nongnu.org, Andrew Melnychenko References: <20231030051356.33123-1-akihiko.odaki@daynix.com> <20231030051356.33123-12-akihiko.odaki@daynix.com> <58fb3b75-dd69-4715-a8ec-4c3df3b7e4c5@daynix.com> <8880b6f9-f556-46f7-a191-eeec0fe208b0@daynix.com> <20231101023805-mutt-send-email-mst@kernel.org> Content-Language: en-US From: Akihiko Odaki In-Reply-To: <20231101023805-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: none client-ip=2607:f8b0:4864:20::42f; envelope-from=akihiko.odaki@daynix.com; helo=mail-pf1-x42f.google.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_NONE=0.001, T_SCC_BODY_TEXT_LINE=-0.01 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 2023/11/01 15:38, Michael S. Tsirkin wrote: > On Wed, Nov 01, 2023 at 01:50:00PM +0900, Akihiko Odaki wrote: >> We had another discussion regarding migration for patch "virtio-net: Do not >> clear VIRTIO_NET_F_HASH_REPORT". It does change the runtime behavior so we >> need to take migration into account. I still think the patch does not >> require a compatibility flag since it only exposes a new feature and does >> not prevent migrating from old QEMU that exposes less features. It instead >> fixes the case where migrating between hosts with different tap feature >> sets. > > When in doubt, add a compat flag. Personally I'm confident about the migration compatibility with patch "virtio-net: Do not clear VIRTIO_NET_F_HASH_REPORT". virtio-net already does the same thing when the tap implementation on the destination implements virtio-net header support while the counterpart of the source does not.