Re: [PATCH v4 9/9] vhost_user.rst: Add MEM_READ/WRITE messages

[Stefan Hajnoczi]

On Mon, Feb 17, 2025 at 05:40:12PM +0100, Albert Esteve wrote:
> Add MEM_READ/WRITE request to the vhost-user
> spec documentation.
> 
> Signed-off-by: Albert Esteve <aest...@redhat.com>
> ---
>  docs/interop/vhost-user.rst | 33 +++++++++++++++++++++++++++++++++
>  1 file changed, 33 insertions(+)
> 
> diff --git a/docs/interop/vhost-user.rst b/docs/interop/vhost-user.rst
> index 96156f1900..9f7a2c4cf7 100644
> --- a/docs/interop/vhost-user.rst
> +++ b/docs/interop/vhost-user.rst
> @@ -391,6 +391,7 @@ In QEMU the vhost-user message is implemented with the 
> following struct:
>            VhostUserTransferDeviceState transfer_state;
>            VhostUserMMap mmap;
>            VhostUserShMemConfig shmem;
> +          VhostUserMemRWMsg mem_rw;

Is this struct defined anywhere in the spec?

>        };
>    } QEMU_PACKED VhostUserMsg;
>  
> @@ -1938,6 +1939,38 @@ is sent by the front-end.
>    given range shall correspond to the entirety of a valid mapped region.
>    A reply is generated indicating whether unmapping succeeded.
>  
> +``VHOST_USER_BACKEND_MEM_READ``
> +  :id: 11
> +  :equivalent ioctl: N/A
> +  :request payload: ``struct VhostUserMemRWMsg``
> +  :reply payload: N/A
> +
> +  When the ``VHOST_USER_PROTOCOL_F_SHMEM`` protocol feature has been
> +  successfully negotiated, this message can be submitted by the backends to
> +  read a memory region that has failed to resolve a translation due to an
> +  incomplete memory table, after another device called
> +  ``VHOST_USER_BACKEND_SHMEM_MAP`` for the same region on a shared
> +  descriptor file.
> +
> +  This mechanism works as a fallback for resolving those memory
> +  accesses and ensure that DMA works with Shared Memory Regions.
> +
> +``VHOST_USER_BACKEND_MEM_WRITE``
> +  :id: 12
> +  :equivalent ioctl: N/A
> +  :request payload: ``struct VhostUserMemRWMsg``
> +  :reply payload: N/A
> +
> +  When the ``VHOST_USER_PROTOCOL_F_SHMEM`` protocol feature has been
> +  successfully negotiated, this message can be submitted by the backends to
> +  write a memory region that has failed due to resolve a translation an
> +  incomplete memory table  after another device called
> +  ``VHOST_USER_BACKEND_SHMEM_MAP`` for the same region on a shared
> +  descriptor file.
> +
> +  This mechanism works as a fallback for resolving those memory
> +  accesses and ensure that DMA works with Shared Memory Regions.
> +
>  .. _reply_ack:
>  
>  VHOST_USER_PROTOCOL_F_REPLY_ACK
> -- 
> 2.48.1
> 

signature.asc
Description: PGP signature