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Tsirkin" , yin31149@gmail.com, Jason Wang , Yajun Wu , Zhu Lingshan , Lei Yang , Dragos Tatulea , Juan Quintela , Laurent Vivier , si-wei.liu@oracle.com, Gautam Dawar Subject: [RFC PATCH 00/18] Map memory at destination .load_setup in vDPA-net migration Date: Thu, 19 Oct 2023 16:34:37 +0200 Message-Id: <20231019143455.2377694-1-eperezma@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.8 Received-SPF: pass client-ip=170.10.133.124; envelope-from=eperezma@redhat.com; helo=us-smtp-delivery-124.mimecast.com 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_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 Current memory operations like pinning may take a lot of time at the=0D destination. Currently they are done after the source of the migration is= =0D stopped, and before the workload is resumed at the destination. This is a= =0D period where neigher traffic can flow, nor the VM workload can continue=0D (downtime).=0D =0D We can do better as we know the memory layout of the guest RAM at the=0D destination from the moment the migration starts. Moving that operation al= lows=0D QEMU to communicate the kernel the maps while the workload is still running= in=0D the source, so Linux can start mapping them. Ideally, all IOMMU is configu= red,=0D but if the vDPA parent driver uses on-chip IOMMU and .set_map we're still=0D saving all the pinning time.=0D =0D Note that further devices setup at the end of the migration may alter the g= uest=0D memory layout. But same as the previous point, many operations are still do= ne=0D incrementally, like memory pinning, so we're saving time anyway.=0D =0D The first bunch of patches just reorganizes the code, so memory related=0D operation parameters are shared between all vhost_vdpa devices. This is=0D because the destination does not know what vhost_vdpa struct will have the= =0D registered listener member, so it is easier to place them in a shared struc= t=0D rather to keep them in vhost_vdpa struct. Future version may squash or omi= t=0D these patches.=0D =0D Only tested with vdpa_sim. I'm sending this before full benchmark, as some = work=0D like [1] can be based on it, and Si-Wei agreed on benchmark this series wit= h=0D his experience.=0D =0D Future directions on top of this series may include:=0D * Iterative migration of virtio-net devices, as it may reduce downtime per = [1].=0D vhost-vdpa net can apply the configuration through CVQ in the destination= =0D while the source is still migrating.=0D * Move more things ahead of migration time, like DRIVER_OK.=0D * Check that the devices of the destination are valid, and cancel the migra= tion=0D in case it is not.=0D =0D [1] https://lore.kernel.org/qemu-devel/6c8ebb97-d546-3f1c-4cdd-54e23a566f61= @nvidia.com/T/=0D =0D Eugenio P=C3=A9rez (18):=0D vdpa: add VhostVDPAShared=0D vdpa: move iova tree to the shared struct=0D vdpa: move iova_range to vhost_vdpa_shared=0D vdpa: move shadow_data to vhost_vdpa_shared=0D vdpa: use vdpa shared for tracing=0D vdpa: move file descriptor to vhost_vdpa_shared=0D vdpa: move iotlb_batch_begin_sent to vhost_vdpa_shared=0D vdpa: move backend_cap to vhost_vdpa_shared=0D vdpa: remove msg type of vhost_vdpa=0D vdpa: move iommu_list to vhost_vdpa_shared=0D vdpa: use VhostVDPAShared in vdpa_dma_map and unmap=0D vdpa: use dev_shared in vdpa_iommu=0D vdpa: move memory listener to vhost_vdpa_shared=0D vdpa: do not set virtio status bits if unneeded=0D vdpa: add vhost_vdpa_load_setup=0D vdpa: add vhost_vdpa_net_load_setup NetClient callback=0D vdpa: use shadow_data instead of first device v->shadow_vqs_enabled=0D virtio_net: register incremental migration handlers=0D =0D include/hw/virtio/vhost-vdpa.h | 43 +++++---=0D include/net/net.h | 4 +=0D hw/net/virtio-net.c | 23 +++++=0D hw/virtio/vdpa-dev.c | 7 +-=0D hw/virtio/vhost-vdpa.c | 183 ++++++++++++++++++---------------=0D net/vhost-vdpa.c | 127 ++++++++++++-----------=0D hw/virtio/trace-events | 14 +--=0D 7 files changed, 239 insertions(+), 162 deletions(-)=0D =0D -- =0D 2.39.3=0D =0D