Add VIRTGPU_PARAM_HOST_PAGE_SIZE as a 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.

Signed-off-by: Sergio Lopez <slp@redhat.com>
---
 drivers/gpu/drm/virtio/virtgpu_ioctl.c | 5 +++++
 include/uapi/drm/virtgpu_drm.h         | 1 +
 2 files changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
index c33c057365f85a2ace536f91655c903036827312..405203b3c3847a8b318a7118aa34356c839d249e 100644
--- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
+++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
@@ -117,6 +117,11 @@ static int virtio_gpu_getparam_ioctl(struct drm_device *dev, void *data,
 	case VIRTGPU_PARAM_EXPLICIT_DEBUG_NAME:
 		value = vgdev->has_context_init ? 1 : 0;
 		break;
+	case VIRTGPU_PARAM_HOST_PAGE_SIZE:
+		if (!vgdev->has_host_page_size)
+			return -EINVAL;
+		value = vgdev->host_page_size;
+		break;
 	default:
 		return -EINVAL;
 	}
diff --git a/include/uapi/drm/virtgpu_drm.h b/include/uapi/drm/virtgpu_drm.h
index c2ce71987e9bb816d13a300679336cb756f1cbcf..505f87263a15f55302d7134335bebd91ff4cdae3 100644
--- a/include/uapi/drm/virtgpu_drm.h
+++ b/include/uapi/drm/virtgpu_drm.h
@@ -98,6 +98,7 @@ struct drm_virtgpu_execbuffer {
 #define VIRTGPU_PARAM_CONTEXT_INIT 6 /* DRM_VIRTGPU_CONTEXT_INIT */
 #define VIRTGPU_PARAM_SUPPORTED_CAPSET_IDs 7 /* Bitmask of supported capability set ids */
 #define VIRTGPU_PARAM_EXPLICIT_DEBUG_NAME 8 /* Ability to set debug name from userspace */
+#define VIRTGPU_PARAM_HOST_PAGE_SIZE 9 /* Host's page size */
 
 struct drm_virtgpu_getparam {
 	__u64 param;

-- 
2.48.1

On 4/2/25 20:46, Sergio Lopez wrote:
> diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> index c33c057365f85a2ace536f91655c903036827312..405203b3c3847a8b318a7118aa34356c839d249e 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> @@ -117,6 +117,11 @@ static int virtio_gpu_getparam_ioctl(struct drm_device *dev, void *data,
>  	case VIRTGPU_PARAM_EXPLICIT_DEBUG_NAME:
>  		value = vgdev->has_context_init ? 1 : 0;
>  		break;
> +	case VIRTGPU_PARAM_HOST_PAGE_SIZE:
> +		if (!vgdev->has_host_page_size)
> +			return -EINVAL;

ENOENT

-- 
Best regards,
Dmitry