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@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/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@xxxxxxxxxx> --- 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, -- Sergio Lopez <slp@xxxxxxxxxx>
