Re: [PATCH v2 1/1] drm/syncobj: add sideband payload

[Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>]

On 08/08/2019 12:42, Lionel Landwerlin wrote:
> On 08/08/2019 12:32, Koenig, Christian wrote:
> > Am 08.08.19 um 11:04 schrieb Lionel Landwerlin:
> > > The Vulkan timeline semaphores allow signaling to happen on the point
> > > of the timeline without all of the its dependencies to be created.
> > >
> > > The current 2 implementations (AMD/Intel) of the Vulkan spec on top of
> > > the Linux kernel are using a thread to wait on the dependencies of a
> > > given point to materialize and delay actual submission to the kernel
> > > driver until the wait completes.
> > >
> > > If a binary semaphore is submitted for signaling along the side of a
> > > timeline semaphore waiting for completion that means that the drm
> > > syncobj associated with that binary semaphore will not have a DMA
> > > fence associated with it by the time vkQueueSubmit() returns. This and
> > > the fact that a binary semaphore can be signaled and unsignaled as
> > > before its DMA fences materialize mean that we cannot just rely on the
> > > fence within the syncobj but we also need a sideband payload verifying
> > > that the fence in the syncobj matches the last submission from the
> > > Vulkan API point of view.
> > >
> > > This change adds a sideband payload that is incremented with signaled
> > > syncobj when vkQueueSubmit() is called. The next vkQueueSubmit()
> > > waiting on a the syncobj will read the sideband payload and wait for a
> > > fence chain element with a seqno superior or equal to the sideband
> > > payload value to be added into the fence chain and use that fence to
> > > trigger the submission on the kernel driver.
> > >
> > > v2: Use a separate ioctl to get/set the sideband value (Christian)
> > >
> > > Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>
> > > Cc: Christian Koenig <Christian.Koenig@xxxxxxx>
> > > Cc: Jason Ekstrand <jason@xxxxxxxxxxxxxx>
> > > Cc: David(ChunMing) Zhou <David1.Zhou@xxxxxxx>
> > > ---
> > >    drivers/gpu/drm/drm_internal.h |  2 ++
> > >    drivers/gpu/drm/drm_ioctl.c    |  3 ++
> > >    drivers/gpu/drm/drm_syncobj.c  | 63 
> > > +++++++++++++++++++++++++++++++---
> > >    include/drm/drm_syncobj.h      |  9 +++++
> > >    include/uapi/drm/drm.h         |  5 ++-
> > >    5 files changed, 77 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/drm_internal.h 
> > > b/drivers/gpu/drm/drm_internal.h
> > > index 51a2055c8f18..de5267711a7c 100644
> > > --- a/drivers/gpu/drm/drm_internal.h
> > > +++ b/drivers/gpu/drm/drm_internal.h
> > > @@ -208,6 +208,8 @@ int drm_syncobj_timeline_signal_ioctl(struct 
> > > drm_device *dev, void *data,
> > >                          struct drm_file *file_private);
> > >    int drm_syncobj_query_ioctl(struct drm_device *dev, void *data,
> > >                    struct drm_file *file_private);
> > > +int drm_syncobj_sideband_ioctl(struct drm_device *dev, void *data,
> > > +                   struct drm_file *file_private);
> > >       /* drm_framebuffer.c */
> > >    void drm_framebuffer_print_info(struct drm_printer *p, unsigned 
> > > int indent,
> > > diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
> > > index f675a3bb2c88..7fd99533f78f 100644
> > > --- a/drivers/gpu/drm/drm_ioctl.c
> > > +++ b/drivers/gpu/drm/drm_ioctl.c
> > > @@ -703,6 +703,9 @@ static const struct drm_ioctl_desc drm_ioctls[] = {
> > >                  DRM_RENDER_ALLOW),
> > >        DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_QUERY, drm_syncobj_query_ioctl,
> > >                  DRM_RENDER_ALLOW),
> > > +    DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_SIDEBAND, 
> > > drm_syncobj_sideband_ioctl,
> > > +              DRM_RENDER_ALLOW),
> > > +
> > >        DRM_IOCTL_DEF(DRM_IOCTL_CRTC_GET_SEQUENCE, 
> > > drm_crtc_get_sequence_ioctl, 0),
> > >        DRM_IOCTL_DEF(DRM_IOCTL_CRTC_QUEUE_SEQUENCE, 
> > > drm_crtc_queue_sequence_ioctl, 0),
> > >        DRM_IOCTL_DEF(DRM_IOCTL_MODE_CREATE_LEASE, 
> > > drm_mode_create_lease_ioctl, DRM_MASTER),
> > > diff --git a/drivers/gpu/drm/drm_syncobj.c 
> > > b/drivers/gpu/drm/drm_syncobj.c
> > > index b927e482e554..66f4f91baa6d 100644
> > > --- a/drivers/gpu/drm/drm_syncobj.c
> > > +++ b/drivers/gpu/drm/drm_syncobj.c
> > > @@ -1150,8 +1150,10 @@ drm_syncobj_reset_ioctl(struct drm_device 
> > > *dev, void *data,
> > >        if (ret < 0)
> > >            return ret;
> > >    -    for (i = 0; i < args->count_handles; i++)
> > > +    for (i = 0; i < args->count_handles; i++) {
> > >            drm_syncobj_replace_fence(syncobjs[i], NULL);
> > > +        syncobjs[i]->sideband_payload = 0;
> > > +    }
> > >           drm_syncobj_array_free(syncobjs, args->count_handles);
> > >    @@ -1205,7 +1207,7 @@ drm_syncobj_timeline_signal_ioctl(struct 
> > > drm_device *dev, void *data,
> > >        if (!drm_core_check_feature(dev, DRIVER_SYNCOBJ_TIMELINE))
> > >            return -EOPNOTSUPP;
> > >    -    if (args->pad != 0)
> > > +    if (args->flags != 0)
> > >            return -EINVAL;
> > >           if (args->count_handles == 0)
> > > @@ -1276,7 +1278,7 @@ int drm_syncobj_query_ioctl(struct drm_device 
> > > *dev, void *data,
> > >        if (!drm_core_check_feature(dev, DRIVER_SYNCOBJ_TIMELINE))
> > >            return -EOPNOTSUPP;
> > >    -    if (args->pad != 0)
> > > +    if (args->flags != 0)
> > >            return -EINVAL;
> > >           if (args->count_handles == 0)
> > > @@ -1312,15 +1314,68 @@ int drm_syncobj_query_ioctl(struct 
> > > drm_device *dev, void *data,
> > >                point = dma_fence_is_signaled(last_signaled) ?
> > >                    last_signaled->seqno :
> > > to_dma_fence_chain(last_signaled)->prev_seqno;
> > > -            dma_fence_put(last_signaled);
> > > +                dma_fence_put(last_signaled);
>
>
> Whoops, I need to drop this.
>
>
> > >            } else {
> > >                point = 0;
> > >            }
> > >            ret = copy_to_user(&points[i], &point, sizeof(uint64_t));
> > >            ret = ret ? -EFAULT : 0;
> > >            if (ret)
> > > +            goto error;
> > > +        break;
> > > +    }
> > > +
> > > +error:
> > > +    drm_syncobj_array_free(syncobjs, args->count_handles);
> > > +
> > > +    return ret;
> > > +}
> > Those changes above to drm_syncobj_query now look completely unrelated
> > to me.
>
>
> The diff is really weird indeed but apart from the mistake above it's 
> right.


Arg no, it was wrong :(


> > > +
> > > +int drm_syncobj_sideband_ioctl(struct drm_device *dev, void *data,
> > > +                   struct drm_file *file_private)
> > > +{
> > > +    struct drm_syncobj_timeline_array *args = data;
> > > +    struct drm_syncobj **syncobjs;
> > > +    uint64_t __user *points = u64_to_user_ptr(args->points);
> > > +    uint32_t i;
> > > +    int ret;
> > > +
> > > +    if (!drm_core_check_feature(dev, DRIVER_SYNCOBJ_TIMELINE))
> > > +        return -EOPNOTSUPP;
> > > +
> > > +    if (args->flags != 
> > > DRM_SYNCOBJ_TIMELINE_ARRAY_GET_SIDEBAND_PAYLOAD &&
> > > +        args->flags != 
> > > DRM_SYNCOBJ_TIMELINE_ARRAY_SET_SIDEBAND_PAYLOAD)
> > > +        return -EINVAL;
> > > +
> > > +    if (args->count_handles == 0)
> > > +        return -EINVAL;
> > > +
> > > +    ret = drm_syncobj_array_find(file_private,
> > > +                     u64_to_user_ptr(args->handles),
> > > +                     args->count_handles,
> > > +                     &syncobjs);
> > > +    if (ret < 0)
> > > +        return ret;
> > > +
> > > +    for (i = 0; i < args->count_handles; i++) {
> > > +        switch (args->flags) {
> > > +        case DRM_SYNCOBJ_TIMELINE_ARRAY_GET_SIDEBAND_PAYLOAD:
> > > +            copy_to_user(&points[i], 
> > > &syncobjs[i]->sideband_payload, sizeof(uint64_t));
> > > +            ret = ret ? -EFAULT : 0;
> > > +            if (ret)
> > > +                goto error;
> > > +            break;
> > > +
> > > +        case DRM_SYNCOBJ_TIMELINE_ARRAY_SET_SIDEBAND_PAYLOAD:
> > > + copy_from_user(&syncobjs[i]->sideband_payload, &points[i], 
> > > sizeof(uint64_t));
> > > +            ret = ret ? -EFAULT : 0;
> > > +            if (ret)
> > > +                goto error;
> > >                break;
> > > +        }
> > >        }
> > > +
> > > +error:
> > >        drm_syncobj_array_free(syncobjs, args->count_handles);
> > >           return ret;
> > > diff --git a/include/drm/drm_syncobj.h b/include/drm/drm_syncobj.h
> > > index 6cf7243a1dc5..b587b8e07547 100644
> > > --- a/include/drm/drm_syncobj.h
> > > +++ b/include/drm/drm_syncobj.h
> > > @@ -61,6 +61,15 @@ struct drm_syncobj {
> > >         * @file: A file backing for this syncobj.
> > >         */
> > >        struct file *file;
> > > +    /**
> > > +     * @sideband_payload: A 64bit side band payload.
> > > +     *
> > > +     * We use the sideband payload value to wait on binary syncobj 
> > > fences
> > > +     * to materialize. It is a reservation mechanism for the 
> > > signaler to
> > > +     * express that at some point in the future a dma fence with 
> > > the same
> > > +     * seqno will be put into the syncobj.
> > > +     */
> > > +    u64 sideband_payload;
> > >    };
> > >       void drm_syncobj_free(struct kref *kref);
> > > diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
> > > index 8a5b2f8f8eb9..dfcbaf603aff 100644
> > > --- a/include/uapi/drm/drm.h
> > > +++ b/include/uapi/drm/drm.h
> > > @@ -782,7 +782,9 @@ struct drm_syncobj_timeline_array {
> > >        __u64 handles;
> > >        __u64 points;
> > >        __u32 count_handles;
> > > -    __u32 pad;
> > > +    __u32 flags;
> > > +#define DRM_SYNCOBJ_TIMELINE_ARRAY_GET_SIDEBAND_PAYLOAD (0)
> > > +#define DRM_SYNCOBJ_TIMELINE_ARRAY_SET_SIDEBAND_PAYLOAD (1)
> > >    };
> > >       @@ -946,6 +948,7 @@ extern "C" {
> > >    #define DRM_IOCTL_SYNCOBJ_QUERY        DRM_IOWR(0xCB, struct 
> > > drm_syncobj_timeline_array)
> > >    #define DRM_IOCTL_SYNCOBJ_TRANSFER    DRM_IOWR(0xCC, struct 
> > > drm_syncobj_transfer)
> > >    #define DRM_IOCTL_SYNCOBJ_TIMELINE_SIGNAL    DRM_IOWR(0xCD, 
> > > struct drm_syncobj_timeline_array)
> > > +#define DRM_IOCTL_SYNCOBJ_SIDEBAND    DRM_IOWR(0xCE, struct 
> > > drm_syncobj_timeline_array)
> > Maybe better add separate get/set IOCTLs, but just a suggestion.
> >
> > Regards,
> > Christian.
>
>
> Alright, I was worried about polluting the ioctl IDs.
>
>
> Did the new tests on the CTS helped reproduce on your side the issue 
> this is solving?
>
>
> Thanks,
>
>
> -Lionel
>
>
> > >       /**
> > >     * Device specific ioctls should only be in their respective headers
>
>
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