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From:   Rob Clark <robdclark@gmail.com>
Date:   Sat, 28 Oct 2023 08:35:54 -0700
Message-ID: <CAF6AEGswNUH6e8HNHMquyv__6kM9Xz39SaZ9n5c4ydrxJz_sig@mail.gmail.com>
Subject: Re: [PATCH] drm/msm/gem: Add metadata
To:     Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc:     dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org,
        linux-arm-msm@vger.kernel.org, Rob Clark <robdclark@chromium.org>,
        Abhinav Kumar <quic_abhinavk@quicinc.com>,
        Sean Paul <sean@poorly.run>,
        Marijn Suijten <marijn.suijten@somainline.org>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        open list <linux-kernel@vger.kernel.org>
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On Fri, Oct 27, 2023 at 6:16=E2=80=AFPM Dmitry Baryshkov
<dmitry.baryshkov@linaro.org> wrote:
>
> 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.

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

> >
> > 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_dr=
v.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 *de=
v, 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 *de=
v, void *data,
> >                 break;
> >         case MSM_INFO_GET_NAME:
> >                 if (args->value && (args->len < strlen(msm_obj->name)))=
 {
> > -                       ret =3D -EINVAL;
> > +                       ret =3D -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 =3D strlen(msm_obj->name);
> > @@ -627,6 +630,58 @@ static int msm_ioctl_gem_info(struct drm_device *d=
ev, void *data,
> >                                          msm_obj->name, args->len))
> >                                 ret =3D -EFAULT;
> >                 }
> > +               break;
> > +       case MSM_INFO_SET_METADATA:
> > +               /* Impose a moderate upper bound on metadata size: */
> > +               if (args->len > 128) {
> > +                       ret =3D -EOVERFLOW;
> > +                       break;
> > +               }
> > +
> > +               ret =3D msm_gem_lock_interruptible(obj);
> > +               if (ret)
> > +                       break;
> > +
> > +               msm_obj->metadata =3D
> > +                       krealloc(msm_obj->metadata, args->len, GFP_KERN=
EL);
> > +               msm_obj->metadata_size =3D args->len;
> > +
> > +               if (copy_from_user(msm_obj->metadata, u64_to_user_ptr(a=
rgs->value),
> > +                                  args->len)) {
> > +                       msm_obj->metadata_size =3D 0;
> > +                       ret =3D -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 conf=
irm
> > +                        * via device and driver UUIDs that the exporte=
r and
> > +                        * importer versions match.  All we can do from=
 the
> > +                        * kernel side is check the length under obj lo=
ck
> > +                        * when userspace tries to retrieve the metadat=
a
> > +                        */
> > +                       args->len =3D msm_obj->metadata_size;
> > +                       break;
> > +               }
> > +
> > +               ret =3D msm_gem_lock_interruptible(obj);
> > +               if (ret)
> > +                       break;
> > +
> > +               if (args->len < msm_obj->metadata_size) {
> > +                       ret =3D -ETOOSMALL;
> > +               } else if (copy_to_user(u64_to_user_ptr(args->value),
> > +                                       msm_obj->metadata, args->len)) =
{
> > +                       ret =3D -EFAULT;
> > +               }
>
> Doesn't checkpwatch warn here about extra curly brackets?

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

BR,
-R

> > +
> > +               msm_gem_unlock(obj);
> > +
> >                 break;
> >         }
> >
> > diff --git a/drivers/gpu/drm/msm/msm_gem.h b/drivers/gpu/drm/msm/msm_ge=
m.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 p=
ointer */
> >  #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