linux-kernel - [PATCH 1/3] drm/virtio: support VIRTIO_GPU_F_BLOB

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Message-ID: <20251110125213.12633-2-slp@redhat.com>
Date: Mon, 10 Nov 2025 13:52:11 +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 1/3] drm/virtio: support VIRTIO_GPU_F_BLOB_ALIGNMENT

Support VIRTIO_GPU_F_BLOB_ALIGNMENT, a feature that indicates the device
provides a valid blob_alignment field in its configuration, and that
both RESOURCE_CREATE_BLOB and RESOURCE_MAP_BLOB requests must be aligned
to that value.

Signed-off-by: Sergio Lopez <slp@...hat.com>
---
 drivers/gpu/drm/virtio/virtgpu_drv.c |  1 +
 drivers/gpu/drm/virtio/virtgpu_drv.h |  2 ++
 drivers/gpu/drm/virtio/virtgpu_kms.c | 14 +++++++++++---
 include/uapi/linux/virtio_gpu.h      |  9 +++++++++
 4 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.c b/drivers/gpu/drm/virtio/virtgpu_drv.c
index 71c6ccad4b99..ad675ee18b01 100644
--- a/drivers/gpu/drm/virtio/virtgpu_drv.c
+++ b/drivers/gpu/drm/virtio/virtgpu_drv.c
@@ -162,6 +162,7 @@ static unsigned int features[] = {
 	VIRTIO_GPU_F_RESOURCE_UUID,
 	VIRTIO_GPU_F_RESOURCE_BLOB,
 	VIRTIO_GPU_F_CONTEXT_INIT,
+	VIRTIO_GPU_F_BLOB_ALIGNMENT,
 };
 static struct virtio_driver virtio_gpu_driver = {
 	.feature_table = features,
diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h
index f17660a71a3e..d1fa386a5a99 100644
--- a/drivers/gpu/drm/virtio/virtgpu_drv.h
+++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
@@ -257,6 +257,7 @@ struct virtio_gpu_device {
 	bool has_resource_blob;
 	bool has_host_visible;
 	bool has_context_init;
+	bool has_blob_alignment;
 	struct virtio_shm_region host_visible_region;
 	struct drm_mm host_visible_mm;
 
@@ -270,6 +271,7 @@ struct virtio_gpu_device {
 	uint32_t num_capsets;
 	uint64_t capset_id_mask;
 	struct list_head cap_cache;
+	uint32_t blob_alignment;
 
 	/* protects uuid state when exporting */
 	spinlock_t resource_export_lock;
diff --git a/drivers/gpu/drm/virtio/virtgpu_kms.c b/drivers/gpu/drm/virtio/virtgpu_kms.c
index 1c15cbf326b7..a20b62041f03 100644
--- a/drivers/gpu/drm/virtio/virtgpu_kms.c
+++ b/drivers/gpu/drm/virtio/virtgpu_kms.c
@@ -123,7 +123,7 @@ int virtio_gpu_init(struct virtio_device *vdev, struct drm_device *dev)
 	struct virtio_gpu_device *vgdev;
 	/* this will expand later */
 	struct virtqueue *vqs[2];
-	u32 num_scanouts, num_capsets;
+	u32 num_scanouts, num_capsets, blob_alignment;
 	int ret = 0;
 
 	if (!virtio_has_feature(vdev, VIRTIO_F_VERSION_1))
@@ -197,14 +197,22 @@ int virtio_gpu_init(struct virtio_device *vdev, struct drm_device *dev)
 	if (virtio_has_feature(vgdev->vdev, VIRTIO_GPU_F_CONTEXT_INIT))
 		vgdev->has_context_init = true;
 
+	if (virtio_has_feature(vgdev->vdev, VIRTIO_GPU_F_BLOB_ALIGNMENT)) {
+		vgdev->has_blob_alignment = true;
+		virtio_cread_le(vgdev->vdev, struct virtio_gpu_config,
+				blob_alignment, &blob_alignment);
+		vgdev->blob_alignment = blob_alignment;
+	}
+
 	DRM_INFO("features: %cvirgl %cedid %cresource_blob %chost_visible",
 		 vgdev->has_virgl_3d    ? '+' : '-',
 		 vgdev->has_edid        ? '+' : '-',
 		 vgdev->has_resource_blob ? '+' : '-',
 		 vgdev->has_host_visible ? '+' : '-');
 
-	DRM_INFO("features: %ccontext_init\n",
-		 vgdev->has_context_init ? '+' : '-');
+	DRM_INFO("features: %ccontext_init %cblob_alignment\n",
+		 vgdev->has_context_init ? '+' : '-',
+		 vgdev->has_blob_alignment ? '+' : '-');
 
 	ret = virtio_find_vqs(vgdev->vdev, 2, vqs, vqs_info, NULL);
 	if (ret) {
diff --git a/include/uapi/linux/virtio_gpu.h b/include/uapi/linux/virtio_gpu.h
index be109777d10d..4f530d90058c 100644
--- a/include/uapi/linux/virtio_gpu.h
+++ b/include/uapi/linux/virtio_gpu.h
@@ -64,6 +64,14 @@
  * context_init and multiple timelines
  */
 #define VIRTIO_GPU_F_CONTEXT_INIT        4
+/*
+ * The device provides a valid blob_alignment
+ * field in its configuration and both
+ * VIRTIO_GPU_CMD_RESOURCE_CREATE_BLOB and
+ * VIRTIO_GPU_CMD_RESOURCE_MAP_BLOB requests
+ * must be aligned to that value.
+ */
+#define VIRTIO_GPU_F_BLOB_ALIGNMENT      5
 
 enum virtio_gpu_ctrl_type {
 	VIRTIO_GPU_UNDEFINED = 0,
@@ -365,6 +373,7 @@ struct virtio_gpu_config {
 	__le32 events_clear;
 	__le32 num_scanouts;
 	__le32 num_capsets;
+	__le32 blob_alignment;
 };
 
 /* simple formats for fbcon/X use */
-- 
2.51.0