Re: [PATCH v2 0/2] drm/virtio: introduce the HOST_PAGE_SIZE feature

[Dmitry Osipenko <dmitry.osipenko@collabora.com>]

On 4/2/25 20:45, Sergio Lopez wrote:
> There's an incresing 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 improve this situation, we introduce here the HOST_PAGE_SIZE feature.
> This feature indicates that the host has an extended virtio_gpu_config
> structure that include it's own page size a new field.
> 
> On the second commit, we also add a new param that can be read with
> VIRTGPU_GETPARAM by userspace applications running in the guest to
> obtain the host's page size and find out the right alignment to be used
> in shared memory allocations.
> 
> There has been a discussion in virtio-comments about whether the
> information about alignment restrictions must be shared in a generic or
> in a device-specific way, favoring the latter:
> 
> https://lore.kernel.org/virtio-comment/CY8PR12MB7195B5E575099CD9CA1F2F39DCAF2@CY8PR12MB7195.namprd12.prod.outlook.com/T/#t
> 
> v2:
>  - Rebase on top of current upstream.
>  - Make a reference in the cover to the discussion about how device
>    page alignment restrictions should be shared with the driver.
> 
> Signed-off-by: Sergio Lopez <slp@redhat.com>
> ---
> Sergio Lopez (2):
>       drm/virtio: introduce the HOST_PAGE_SIZE feature
>       drm/virtio: add VIRTGPU_PARAM_HOST_PAGE_SIZE 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 |  5 +++++
>  drivers/gpu/drm/virtio/virtgpu_kms.c   | 13 ++++++++++---
>  include/uapi/drm/virtgpu_drm.h         |  1 +
>  include/uapi/linux/virtio_gpu.h        |  5 +++++
>  6 files changed, 24 insertions(+), 3 deletions(-)
> ---
> base-commit: acc4d5ff0b61eb1715c498b6536c38c1feb7f3c1
> change-id: 20250402-virtio-gpu-host-page-size-282c99dfe44c
> 
> Best regards,

Hi Sergio,

Curious if this feature still wanted. The protocol was updated many
months ago with the VIRTIO_GPU_F_BLOB_ALIGNMENT addition.

-- 
Best regards,
Dmitry