[PATCH v2 0/3] drm/virtio: introduce F_BLOB_ALIGNMENT support

[Sergio Lopez <slp@redhat.com>]

There's an increasing number of machines supporting multiple page sizes
and on these machines the host and a guest can be running, each one,
with a different page size.

For what pertains to virtio-gpu, this is not a problem if the page size
of the guest happens to be bigger or equal than the host, but will
potentially lead to failures in memory allocations and/or mappings
otherwise.

To deal with this, the virtio-spec was extended to introduce with the
VIRTIO_GPU_F_BLOB_ALIGNMENT feature [1]. If this feature is negotiated,
we must use the "blob_alignment" field in the config to ensure every
CREATE_BLOB and MAP_BLOB is properly aligned before sending it to the
device.

We also introduce the VIRTGPU_PARAM_BLOB_ALIGNMENT parameter to allow
userspace to query the alignment restrictions for blobs.

This supersedes "drm/virtio: introduce the HOST_PAGE_SIZE feature" [2].

[1] https://github.com/oasis-tcs/virtio-spec/commit/f9abfd55cb663837dda1153b826216dcf4d25b84
[2] https://lkml.org/lkml/2024/7/23/438

Changes in v2:
- Rebased.
- Moved blob size alignment validation to verify_blob(), rejecting
misaligned sizes early in the ioctl path instead of checking in
virtio_gpu_cmd_resource_create_blob() and virtio_gpu_cmd_map()
(Dmitry Osipenko).

Sergio Lopez (3):
  drm/virtio: support VIRTIO_GPU_F_BLOB_ALIGNMENT
  drm/virtio: honor blob_alignment requirements
  drm/virtio: add VIRTGPU_PARAM_BLOB_ALIGNMENT to params

 drivers/gpu/drm/virtio/virtgpu_drv.c   |  1 +
 drivers/gpu/drm/virtio/virtgpu_drv.h   |  2 ++
 drivers/gpu/drm/virtio/virtgpu_ioctl.c | 10 ++++++++++
 drivers/gpu/drm/virtio/virtgpu_kms.c   | 14 +++++++++++---
 include/uapi/drm/virtgpu_drm.h         |  1 +
 include/uapi/linux/virtio_gpu.h        |  9 +++++++++
 6 files changed, 34 insertions(+), 3 deletions(-)

-- 
2.53.0