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

From: Rob Clark
Date: Sat Oct 28 2023 - 11:36:14 EST

On Fri, Oct 27, 2023 at 6:16 PM Dmitry Baryshkov
<dmitry.baryshkov@xxxxxxxxxx> wrote:
>
> On Fri, 27 Oct 2023 at 22:45, Rob Clark <robdclark@xxxxxxxxx> wrote:
> >
> > From: Rob Clark <robdclark@xxxxxxxxxxxx>
> >
> > 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.

jfyi, userspace side of this at:
https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25945

> >
> > Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
> > ---
> > 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/

fair, although it was changed for consistency with GET_METADATA

> > 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?

It might.. it is one of the many checkpatch warnings that I dutifully ignore ;-)

BR,
-R

> > +
> > + 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