Hi all, 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 device. The implementation introduces a robust QOM-based architecture for managing shared memory lifecycle: - VhostUserShmemObject: an intermediate object that manages individual memory mappings - VIRTIO Shared Memory Regions: generic container regions declared in VirtIODevice to support 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 VhostUserShmemObject 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 and includes SHMEM_CONFIG QTest validation. Albert Esteve (8): 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 tests/qtest: Add GET_SHMEM validation test qmp: add shmem feature map vhost-user-device: Add shared memory BAR docs/interop/vhost-user.rst | 101 +++++++++ hw/virtio/meson.build | 1 + hw/virtio/vhost-user-base.c | 49 ++++- hw/virtio/vhost-user-device-pci.c | 34 ++- hw/virtio/vhost-user-shmem.c | 134 ++++++++++++ hw/virtio/vhost-user.c | 250 +++++++++++++++++++++- hw/virtio/virtio-qmp.c | 3 + hw/virtio/virtio.c | 109 ++++++++++ include/hw/virtio/vhost-backend.h | 10 + include/hw/virtio/vhost-user-shmem.h | 75 +++++++ include/hw/virtio/vhost-user.h | 1 + include/hw/virtio/virtio.h | 95 ++++++++ subprojects/libvhost-user/libvhost-user.c | 70 ++++++ subprojects/libvhost-user/libvhost-user.h | 54 +++++ tests/qtest/vhost-user-test.c | 91 ++++++++ 15 files changed, 1070 insertions(+), 7 deletions(-) create mode 100644 hw/virtio/vhost-user-shmem.c create mode 100644 include/hw/virtio/vhost-user-shmem.h -- 2.49.0
