On Wed, Sep 10, 2025 at 1:54 PM Albert Esteve <[email protected]> wrote: > > Hi all, > > v7->v8 > - Unified VhostUserShmemObject and VirtioSharedMemoryMapping > - Refined shmem_obj lifecycle by transferring ownership > - Other small improvements > v6->v7 > - Fixed vhost_user_shmem_object_new to use > memory_region_init_ram_from_fd as before > v5->v6 > - Added intermediate QOM object to manage shared MemoryRegion lifecycle > with reference counting, and automatic cleanup > - Resolved BAR conflict, change from 2 to 3 to avoid conflict with > `modern-pio-notify=on` > - Added SHMEM_CONFIG validation in vhost-user-test > - Changed VirtSharedMemory -> VirtioSharedMemory > - Changed MappedMemoryRegion -> VirtioSharedMemoryMapping > - Changed from heap-allocated MemoryRegion *mr to embedded MemoryRegion > mr in VirtioSharedMemory structure to eliminate memory leaks and > simplify cleanup > - Fixed VirtioSharedMemory initialization and cleanup with > memory_region_init() and object_unparent() > - Other minor fixes, typos, and updates. > > 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.
Small bump to avoid this patch series falling too much. > > The implementation has been tested with rust-vmm based backends and > includes SHMEM_CONFIG QTest validation. > > 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-device-pci.c | 34 ++- > hw/virtio/vhost-user.c | 249 +++++++++++++++++++++- > hw/virtio/virtio-qmp.c | 3 + > hw/virtio/virtio.c | 198 +++++++++++++++++ > 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, 898 insertions(+), 7 deletions(-) > > -- > 2.49.0 >
