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Thu, 19 Feb 2026 13:03:43 +0000 (UTC) Received: from fedora.redhat.com (unknown [10.44.33.19]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 7609D1955F01; Thu, 19 Feb 2026 13:03:36 +0000 (UTC) From: Albert Esteve To: qemu-devel@nongnu.org Cc: Peter Xu , Pierrick Bouvier , mst@redhat.com, dbassey@redhat.com, =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , =?UTF-8?q?Alex=20Benn=C3=A9e?= , Paolo Bonzini , Fabiano Rosas , stefanha@redhat.com, manos.pitsidianakis@linaro.org, Stefano Garzarella , jasowang@redhat.com, Laurent Vivier , slp@redhat.com, hi@alyssa.is, stevensd@chromium.org Subject: [PATCH v13 0/7] vhost-user: Add SHMEM_MAP/UNMAP requests Date: Thu, 19 Feb 2026 14:03:27 +0100 Message-ID: <20260219130334.787858-1-aesteve@redhat.com> Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Received-SPF: pass client-ip=170.10.129.124; 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=-0.045, 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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_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: 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 Hi all, v12-v13 - SMEM_UNMAP spec update to explicitly state the use of VHOST_USER_PROTOCOL_F_REPLY_ACK for replies - Removed confusing remark for 0-sized regions in GET_SHMEM_CONFIG v11->v12 - Refined VIRTIO Shared Memory Region configuration mem size spec description - Removed unused name in vhost-user-base's vub_device_realize to avoid build error - Initialize shmem in vhost_user_backend_handle_shmem_unmap to avoid compiler being confused - Added stub for memory_region_init_ram_from_fd in memory.h for windows builds - Use memory_region_size for shmem_region handlers instead of accessing size member directly in shmem mrs v10->v11 - Rebase to grab commit fde5930cc37175cfcd0f03a089e26f4458a52311 and explicitly unset reply_ack on the SHMEM_MAP/UNMAP msg. - Mention mapping cleanup on device reset in the spec. v9->v10 - Fix transaction_commit invoked without transaction_begin on vhost_user_backend_handle_shmem_map() early errors - Removed fd tracking on VirtioSharedMemoryMapping, it is handled by the RAMBlock - Reject invalid BAR configurations when VIRTIO Shared Memory Regions are in use by vhost-user-test-device 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 | 104 +++++++++ hw/virtio/vhost-user-base.c | 46 +++- hw/virtio/vhost-user-test-device-pci.c | 38 ++- hw/virtio/vhost-user.c | 269 ++++++++++++++++++++++ hw/virtio/virtio-qmp.c | 3 + hw/virtio/virtio.c | 201 ++++++++++++++++ include/hw/virtio/vhost-backend.h | 10 + include/hw/virtio/vhost-user.h | 1 + include/hw/virtio/virtio.h | 137 +++++++++++ include/system/memory.h | 13 ++ subprojects/libvhost-user/libvhost-user.c | 70 ++++++ subprojects/libvhost-user/libvhost-user.h | 54 +++++ 12 files changed, 941 insertions(+), 5 deletions(-) -- 2.52.0