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.

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

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

On Tue, Dec 2, 2025 at 8:50 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> 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.

Release happened already iianm?
Sending the ping.

>
>
> > 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
>