On Tue, Nov 11, 2025 at 10:10:51AM +0100, Albert Esteve wrote: > Hi all, > > 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 > 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.
Looks good, we are in freeze so will merge after 10.2. If it's not too much trouble, pls ping me after the release to help make sure it's not forgotten. > 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 | 102 ++++++++ > hw/virtio/vhost-user-base.c | 47 +++- > hw/virtio/vhost-user-test-device-pci.c | 39 +++- > hw/virtio/vhost-user.c | 269 ++++++++++++++++++++++ > hw/virtio/virtio-qmp.c | 3 + > hw/virtio/virtio.c | 199 ++++++++++++++++ > include/hw/virtio/vhost-backend.h | 10 + > include/hw/virtio/vhost-user.h | 1 + > include/hw/virtio/virtio.h | 137 +++++++++++ > subprojects/libvhost-user/libvhost-user.c | 70 ++++++ > subprojects/libvhost-user/libvhost-user.h | 54 +++++ > 11 files changed, 926 insertions(+), 5 deletions(-) > > -- > 2.49.0
