Re: [PATCH] drm/msm/gem: Add metadata

Dmitry Baryshkov
2023-10-28T01:16:58Z

On Fri, 27 Oct 2023 at 22:45, Rob Clark <robdclark@gmail.com> wrote:
>
> From: Rob Clark <robdclark@chromium.org>
>
> The EXT_external_objects extension is a bit awkward as it doesn't pass
> explicit modifiers, leaving the importer to guess with incomplete
> information. In the case of vk (turnip) exporting and gl (freedreno)
> importing, the "OPTIMAL_TILING_EXT" layout depends on VkImageCreateInfo
> flags (among other things), which the importer does not know. Which
> unfortunately leaves us with the need for a metadata back-channel.
>
> The contents of the metadata are defined by userspace. The
> EXT_external_objects extension is only required to work between
> compatible versions of gl and vk drivers, as defined by device and
> driver UUIDs.
>
> Signed-off-by: Rob Clark <robdclark@chromium.org>
> ---
> drivers/gpu/drm/msm/msm_drv.c | 59 +++++++++++++++++++++++++++++++++--
> drivers/gpu/drm/msm/msm_gem.h | 4 +++
> include/uapi/drm/msm_drm.h | 2 ++
> 3 files changed, 63 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
> index b61ccea05327..8fe2677ea37a 100644
> --- a/drivers/gpu/drm/msm/msm_drv.c
> +++ b/drivers/gpu/drm/msm/msm_drv.c
> @@ -37,9 +37,10 @@
> * - 1.9.0 - Add MSM_SUBMIT_FENCE_SN_IN
> * - 1.10.0 - Add MSM_SUBMIT_BO_NO_IMPLICIT
> * - 1.11.0 - Add wait boost (MSM_WAIT_FENCE_BOOST, MSM_PREP_BOOST)
> + * - 1.12.0 - Add MSM_INFO_SET_METADATA and MSM_INFO_GET_METADATA
> */
> #define MSM_VERSION_MAJOR 1
> -#define MSM_VERSION_MINOR 10
> +#define MSM_VERSION_MINOR 12
> #define MSM_VERSION_PATCHLEVEL 0
>
> static void msm_deinit_vram(struct drm_device *ddev);
> @@ -566,6 +567,8 @@ static int msm_ioctl_gem_info(struct drm_device *dev, void *data,
> break;
> case MSM_INFO_SET_NAME:
> case MSM_INFO_GET_NAME:
> + case MSM_INFO_SET_METADATA:
> + case MSM_INFO_GET_METADATA:
> break;
> default:
> return -EINVAL;
> @@ -618,7 +621,7 @@ static int msm_ioctl_gem_info(struct drm_device *dev, void *data,
> break;
> case MSM_INFO_GET_NAME:
> if (args->value && (args->len < strlen(msm_obj->name))) {
> - ret = -EINVAL;
> + ret = -ETOOSMALL;

This is unrelated and it also slightly changes user interface, so it
IMO should come as a separate commit/

> break;
> }
> args->len = strlen(msm_obj->name);
> @@ -627,6 +630,58 @@ static int msm_ioctl_gem_info(struct drm_device *dev, void *data,
> msm_obj->name, args->len))
> ret = -EFAULT;
> }
> + break;
> + case MSM_INFO_SET_METADATA:
> + /* Impose a moderate upper bound on metadata size: */
> + if (args->len > 128) {
> + ret = -EOVERFLOW;
> + break;
> + }
> +
> + ret = msm_gem_lock_interruptible(obj);
> + if (ret)
> + break;
> +
> + msm_obj->metadata =
> + krealloc(msm_obj->metadata, args->len, GFP_KERNEL);
> + msm_obj->metadata_size = args->len;
> +
> + if (copy_from_user(msm_obj->metadata, u64_to_user_ptr(args->value),
> + args->len)) {
> + msm_obj->metadata_size = 0;
> + ret = -EFAULT;
> + }
> +
> + msm_gem_unlock(obj);
> +
> + break;
> + case MSM_INFO_GET_METADATA:
> + if (!args->value) {
> + /*
> + * Querying the size is inherently racey, but
> + * EXT_external_objects expects the app to confirm
> + * via device and driver UUIDs that the exporter and
> + * importer versions match. All we can do from the
> + * kernel side is check the length under obj lock
> + * when userspace tries to retrieve the metadata
> + */
> + args->len = msm_obj->metadata_size;
> + break;
> + }
> +
> + ret = msm_gem_lock_interruptible(obj);
> + if (ret)
> + break;
> +
> + if (args->len < msm_obj->metadata_size) {
> + ret = -ETOOSMALL;
> + } else if (copy_to_user(u64_to_user_ptr(args->value),
> + msm_obj->metadata, args->len)) {
> + ret = -EFAULT;
> + }

Doesn't checkpwatch warn here about extra curly brackets?

> +
> + msm_gem_unlock(obj);
> +
> break;
> }
>
> diff --git a/drivers/gpu/drm/msm/msm_gem.h b/drivers/gpu/drm/msm/msm_gem.h
> index 7f34263048a3..8d414b072c29 100644
> --- a/drivers/gpu/drm/msm/msm_gem.h
> +++ b/drivers/gpu/drm/msm/msm_gem.h
> @@ -109,6 +109,10 @@ struct msm_gem_object {
>
> char name[32]; /* Identifier to print for the debugfs files */
>
> + /* userspace metadata backchannel */
> + void *metadata;
> + u32 metadata_size;
> +
> /**
> * pin_count: Number of times the pages are pinned
> *
> diff --git a/include/uapi/drm/msm_drm.h b/include/uapi/drm/msm_drm.h
> index 6c34272a13fd..6f2a7ad04aa4 100644
> --- a/include/uapi/drm/msm_drm.h
> +++ b/include/uapi/drm/msm_drm.h
> @@ -139,6 +139,8 @@ struct drm_msm_gem_new {
> #define MSM_INFO_GET_NAME 0x03 /* get debug name, returned by pointer */
> #define MSM_INFO_SET_IOVA 0x04 /* set the iova, passed by value */
> #define MSM_INFO_GET_FLAGS 0x05 /* get the MSM_BO_x flags */
> +#define MSM_INFO_SET_METADATA 0x06 /* set userspace metadata */
> +#define MSM_INFO_GET_METADATA 0x07 /* get userspace metadata */
>
> struct drm_msm_gem_info {
> __u32 handle; /* in */
> --
> 2.41.0
>

--
With best wishes
Dmitry