[RFC PATCH 0/1] vhost-user: Add SHMEM_MAP/UNMAP requests

[Albert Esteve <aesteve@redhat.com>]

Hi all,

This is an early attempt to have backends
support dynamic fd mapping into shared
memory regions. As such, there are a few
things that need settling, so I wanted to
post this first to have some early feedback.

The usecase for this is, e.g., to support
vhost-user-gpu RESOURCE_BLOB operations,
or DAX Window request for virtio-fs. In
general, any operation where a backend
would need to mmap an fd to a shared
memory so that the guest can access it.
The request will be processed by the VMM,
that will, in turn, trigger a mmap with
the instructed parameters (i.e., shmid,
shm_offset, fd_offset, fd, lenght).

As there are already a couple devices
that could benefit of such a feature,
and more could require it in the future,
my intention was to make it generic.

To that end, I declared the shared
memory region list in `VirtIODevice`.
I could add a couple commodity
functions to add new regions to the list,
so that the devices can use them. But
I wanted to gather some feedback before
refining it further, as I am probably
missing some required steps/or security
concerns that I am not taking into account.

Albert Esteve (1):
  vhost-user: add shmem mmap request

 docs/interop/vhost-user.rst |  23 ++++++++
 hw/virtio/vhost-user.c      | 106 ++++++++++++++++++++++++++++++++++++
 hw/virtio/virtio.c          |   2 +
 include/hw/virtio/virtio.h  |   3 +
 4 files changed, 134 insertions(+)

-- 
2.44.0