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.

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

On Wed, Sep 10, 2025 at 1:54 PM Albert Esteve <aesteve@redhat.com> 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
>

On Fri, Sep 26, 2025 at 10:28:07AM +0200, Albert Esteve wrote:
> On Wed, Sep 10, 2025 at 1:54 PM Albert Esteve <aesteve@redhat.com> 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.

Sorry for the slow review. I've finished now.

Stefan