Re: [PATCH v13 3/7] vhost_user.rst: Add SHMEM_MAP/_UNMAP to spec

[Stefano Garzarella <sgarzare@redhat.com>]

On Wed, Mar 04, 2026 at 11:23:42AM +0100, Albert Esteve wrote:
>On Wed, Mar 4, 2026 at 10:46 AM Albert Esteve <aesteve@redhat.com> wrote:
>>
>> On Thu, Feb 19, 2026 at 2:04 PM Albert Esteve <aesteve@redhat.com> wrote:
>> >
>> > Add SHMEM_MAP/_UNMAP request to the vhost-user
>> > spec documentation.
>> >
>> > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
>> > Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
>> > Signed-off-by: Albert Esteve <aesteve@redhat.com>
>> > ---
>> >  docs/interop/vhost-user.rst | 61 +++++++++++++++++++++++++++++++++++++
>> >  1 file changed, 61 insertions(+)
>> >
>> > diff --git a/docs/interop/vhost-user.rst b/docs/interop/vhost-user.rst
>> > index 17a68a62eb..ae4ad6f441 100644
>> > --- a/docs/interop/vhost-user.rst
>> > +++ b/docs/interop/vhost-user.rst
>> > @@ -350,6 +350,27 @@ Device state transfer parameters
>> >    In the future, additional phases might be added e.g. to allow
>> >    iterative migration while the device is running.
>> >
>> > +MMAP request
>> > +^^^^^^^^^^^^
>> > +
>> > ++-------+---------+-----------+------------+-----+-------+
>> > +| shmid | padding | fd_offset | shm_offset | len | flags |
>> > ++-------+---------+-----------+------------+-----+-------+
>> > +
>> > +:shmid: a 8-bit shared memory region identifier
>> > +
>> > +:fd_offset: a 64-bit offset of this area from the start
>> > +            of the supplied file descriptor
>> > +
>> > +:shm_offset: a 64-bit offset from the start of the
>> > +             pointed shared memory region
>> > +
>> > +:len: a 64-bit size of the memory to map
>> > +
>> > +:flags: a 64-bit value:
>> > +  - 0: Pages are mapped read-only
>> > +  - 1: Pages are mapped read-write
>> > +
>> >  C structure
>> >  -----------
>> >
>> > @@ -375,6 +396,7 @@ In QEMU the vhost-user message is implemented with the following struct:
>> >            VhostUserInflight inflight;
>> >            VhostUserShared object;
>> >            VhostUserTransferDeviceState transfer_state;
>> > +          VhostUserMMap mmap;
>> >        };
>> >    } QEMU_PACKED VhostUserMsg;
>> >
>> > @@ -1064,6 +1086,7 @@ Protocol features
>> >    #define VHOST_USER_PROTOCOL_F_XEN_MMAP             17
>> >    #define VHOST_USER_PROTOCOL_F_SHARED_OBJECT        18
>> >    #define VHOST_USER_PROTOCOL_F_DEVICE_STATE         19
>> > +  #define VHOST_USER_PROTOCOL_F_SHMEM                20
>>
>> Commit cda83adc62b6108afc8a82d0f54d9a9a861e7aa8 got upstream first and
>> took feature number 20, so this should be 21 now.
>>
>> @Michael Tsirkin Is it worth sending a new version or will you handle
>> the change?
>
>Sorry, I meant e0822e6085aecc15e2cfb2914d8cd827abae0249 (vhost-user:
>introduce protocol feature for skip drain on GET_VRING_BASE).
>
>But the question remains.

Maybe better to rebase to simplify Michael's life.

BTW this pach LGTM:

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>