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Wed, 03 Jun 2026 13:49:39 -0700 (PDT) X-Received: by 2002:a05:620a:6908:b0:912:c0b3:7d99 with SMTP id af79cd13be357-9158a674e2fmr865915185a.2.1780519778587; Wed, 03 Jun 2026 13:49:38 -0700 (PDT) Received: from x1.local ([142.189.10.167]) by smtp.gmail.com with ESMTPSA id af79cd13be357-9158a3e35dbsm351132085a.42.2026.06.03.13.49.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Jun 2026 13:49:37 -0700 (PDT) Date: Wed, 3 Jun 2026 16:49:36 -0400 From: Peter Xu To: Avihai Horon Cc: qemu-devel@nongnu.org, Alex Williamson , =?utf-8?Q?C=C3=A9dric?= Le Goater , Fabiano Rosas , Pierrick Bouvier , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Zhao Liu , Halil Pasic , Christian Borntraeger , Jason Herne , Richard Henderson , Ilya Leoshkevich , David Hildenbrand , Eric Farman , Matthew Rosato , Cornelia Huck , Eric Blake , Vladimir Sementsov-Ogievskiy , John Snow , Markus Armbruster , Maor Gottlieb Subject: Re: [PATCH v2 11/13] vfio/migration: Implement VFIO_PRECOPY_INFO_REINIT feature Message-ID: References: <20260602092621.382-1-avihaih@nvidia.com> <20260602092621.382-12-avihaih@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260602092621.382-12-avihaih@nvidia.com> Received-SPF: pass client-ip=170.10.133.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.445, 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_PASS=-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: qemu development 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 Tue, Jun 02, 2026 at 12:26:19PM +0300, Avihai Horon wrote: > According to VFIO uAPI, precopy initial_bytes is considered as critical > data that should be transferred and loaded prior to moving to STOP_COPY > state to ensure precopy phase would be effective. > > As currently defined, initial_bytes can only decrease as it's being read > from the data fd. However, there are cases where a new chunk of > initial_bytes should be transferred during precopy. > > The new VFIO_PRECOPY_INFO_REINIT feature addresses this and allows > reporting a new value for initial_bytes regardless of any previously > reported values. > > Implement VFIO_PRECOPY_INFO_REINIT feature: > 1. Opt-in for VFIO_DEVICE_FEATURE_MIG_PRECOPY_INFOv2 to make > VFIO_PRECOPY_INFO_REINIT available. > 2. Request a new switchover ACK if initial_bytes increases post of a > previous switchover ACK. This ensures the device is not moved to > STOP_COPY before initial_bytes has reached zero again. > > Signed-off-by: Avihai Horon Acked-by: Peter Xu -- Peter Xu