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Tsirkin" , stefanha@redhat.com, Stefano Garzarella , slp@redhat.com, dbassey@redhat.com, Albert Esteve Subject: [PATCH v9 0/7] vhost-user: Add SHMEM_MAP/UNMAP requests Date: Wed, 15 Oct 2025 10:59:23 +0200 Message-ID: <20251015085930.1517330-1-aesteve@redhat.com> Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass client-ip=170.10.133.124; envelope-from=aesteve@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, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=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: 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 Hi all, v8->v9 - Fixed vhost-user new handlers to ensure that they always reply - Made MMAP request flags field u64 everywhere - Fixed double memory_region_del_subregion() on UNMAP - Add mappings cleaning on virtio_reset() - Some small typos and fixes - Fixed virtio pci bar mapping for vhost-user-test-device v7->v8 - Unified VhostUserShmemObject and VirtioSharedMemoryMapping - Refined shmem_obj lifecycle by transferring ownership - Other small improvements This patch series implements dynamic fd-backed memory mapping support for vhost-user backends, enabling backends to dynamically request memory mappings and unmappings during runtime through the new VHOST_USER_BACKEND_SHMEM_MAP/UNMAP protocol messages. This feature benefits various VIRTIO devices that require dynamic shared memory management, including virtiofs (for DAX mappings), virtio-gpu (for resource sharing), and the recently standardized virtio-media. The implementation introduces a QOM-based architecture for managing shared memory lifecycle: - VirtioSharedMemoryMapping: an intermediate object that manages individual memory mappings by acting as generic container for regions declared in any vhost-user device type - Dynamic Mapping: backends can request mappings via SHMEM_MAP messages, with the frontend creating MemoryRegions from the provided file descriptors and adding them as subregions When a SHMEM_MAP request is received, the frontend: 1. Creates VirtioSharedMemoryMapping to manage the mapping lifecycle 2. Maps the provided fd with memory_region_init_ram_from_fd() 3. Creates a MemoryRegion backed by the mapped memory 4. Adds it as a subregion of the appropiate VIRTIO Shared Memory Region The QOM reference counting ensures automatic cleanup when mappings are removed or the device is destroyed. This patch also includes: - VHOST_USER_GET_SHMEM_CONFIG: a new frontend request allowing generic vhost-user devices to query shared memory configuration from backends at device initialization, enabling the generic vhost-user-device frontend to work with any backend regardless of specific shared memory requirements. The implementation has been tested with rust-vmm based backends. Albert Esteve (7): vhost-user: Add VirtIO Shared Memory map request vhost_user.rst: Align VhostUserMsg excerpt members vhost_user.rst: Add SHMEM_MAP/_UNMAP to spec vhost_user: Add frontend get_shmem_config command vhost_user.rst: Add GET_SHMEM_CONFIG message qmp: add shmem feature map vhost-user-device: Add shared memory BAR docs/interop/vhost-user.rst | 101 +++++++++ hw/virtio/vhost-user-base.c | 47 +++- hw/virtio/vhost-user-test-device-pci.c | 35 ++- hw/virtio/vhost-user.c | 257 ++++++++++++++++++++++ hw/virtio/virtio-qmp.c | 3 + hw/virtio/virtio.c | 207 +++++++++++++++++ include/hw/virtio/vhost-backend.h | 10 + include/hw/virtio/vhost-user.h | 1 + include/hw/virtio/virtio.h | 138 ++++++++++++ subprojects/libvhost-user/libvhost-user.c | 70 ++++++ subprojects/libvhost-user/libvhost-user.h | 54 +++++ 11 files changed, 918 insertions(+), 5 deletions(-) -- 2.49.0