linux-kernel - [PATCH 0/3] drm/virtio: introduce F_BLOB

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Message-ID: <20251110125213.12633-1-slp@redhat.com>
Date: Mon, 10 Nov 2025 13:52:10 +0100
From: Sergio Lopez <slp@...hat.com>
To: David Airlie <airlied@...hat.com>,
	Gerd Hoffmann <kraxel@...hat.com>,
	Dmitry Osipenko <dmitry.osipenko@...labora.com>,
	Gurchetan Singh <gurchetansingh@...omium.org>,
	Chia-I Wu <olvaffe@...il.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	Simona Vetter <simona@...ll.ch>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Jason Wang <jasowang@...hat.com>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Eugenio Pérez <eperezma@...hat.com>,
	dri-devel@...ts.freedesktop.org,
	virtualization@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Cc: Sergio Lopez <slp@...hat.com>
Subject: [PATCH 0/3] drm/virtio: introduce F_BLOB_ALIGNMENT support

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 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

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    |  4 +++-
 drivers/gpu/drm/virtio/virtgpu_ioctl.c  |  5 +++++
 drivers/gpu/drm/virtio/virtgpu_kms.c    | 14 +++++++++++---
 drivers/gpu/drm/virtio/virtgpu_object.c |  6 ++++--
 drivers/gpu/drm/virtio/virtgpu_prime.c  |  7 +++++--
 drivers/gpu/drm/virtio/virtgpu_vq.c     | 12 +++++++++++-
 drivers/gpu/drm/virtio/virtgpu_vram.c   | 10 ++++++++--
 include/uapi/drm/virtgpu_drm.h          |  1 +
 include/uapi/linux/virtio_gpu.h         |  9 +++++++++
 10 files changed, 58 insertions(+), 11 deletions(-)

-- 
2.51.0