On Fri, Aug 9, 2019 at 8:43 AM Lionel Landwerlin <
lionel.g.landwer...@intel.com> wrote:
> 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)
>
> v3: Use 2 ioctls for get/set (Christian)
>
> v4: Use a single new ioctl
>
> v5: a bunch of blattant mistakes
> Store payload atomically (Chris)
>
> Signed-off-by: Lionel Landwerlin <lionel.g.landwer...@intel.com>
> Cc: Christian Koenig <christian.koe...@amd.com>
> Cc: Jason Ekstrand <ja...@jlekstrand.net>
> Cc: David(ChunMing) Zhou <david1.z...@amd.com>
> ---
> drivers/gpu/drm/drm_internal.h | 2 ++
> drivers/gpu/drm/drm_ioctl.c | 3 ++
> drivers/gpu/drm/drm_syncobj.c | 58 +++++++++++++++++++++++++++++++++-
> include/drm/drm_syncobj.h | 9 ++++++
> include/uapi/drm/drm.h | 17 ++++++++++
> 5 files changed, 88 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_internal.h
> b/drivers/gpu/drm/drm_internal.h
> index 51a2055c8f18..e297dfd85019 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_binary_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..644d0bc800a4 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_BINARY, drm_syncobj_binary_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..d2d3a8d1374d 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);
> + atomic64_set(&syncobjs[i]->binary_payload, 0);
> + }
>
> drm_syncobj_array_free(syncobjs, args->count_handles);
>
> @@ -1321,6 +1323,60 @@ int drm_syncobj_query_ioctl(struct drm_device *dev,
> void *data,
> if (ret)
> break;
> }
> +
> + drm_syncobj_array_free(syncobjs, args->count_handles);
> +
> + return ret;
> +}
> +
> +int drm_syncobj_binary_ioctl(struct drm_device *dev, void *data,
> + struct drm_file *file_private)
> +{
> + struct drm_syncobj_binary_array *args = data;
> + struct drm_syncobj **syncobjs;
> + u32 __user *access_flags = u64_to_user_ptr(args->access_flags);
> + u64 __user *values = u64_to_user_ptr(args->values);
> + u32 i;
> + int ret;
> +
> + if (!drm_core_check_feature(dev, DRIVER_SYNCOBJ_TIMELINE))
> + return -EOPNOTSUPP;
> +
> + if (args->pad != 0)
> + 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++) {
> + u32 flags;
> +
> + if (get_user(flags, &access_flags[i])) {
> + ret = -EFAULT;
> + break;
> + }
> +
> +
> + if (flags & DRM_SYNCOBJ_BINARY_VALUE_READ) {
> + u64 value =
> atomic64_read(&syncobjs[i]->binary_payload);
> +
> + if (put_user(value, &values[i])) {
> + ret = -EFAULT;
> + break;
> + }
> + }
> +
> + if (flags & DRM_SYNCOBJ_BINARY_VALUE_INC)
> + atomic64_inc(&syncobjs[i]->binary_payload);
>
You go out of your way to use atomics but then don't bother to do the read
and increment atomically. Maybe something like
u64 value = 0;
if (flags & DRM_SYNCOBJ_BINARY_VALUE_INC)
value = atomic64_inc(...);
else if (flags & DRM_SYNCOBJ_BINARY_VALUE_READ)
value = atomic64_read(...);
if (flags & DRM_SYNCOBJ_BINARY_VALUE_READ)
put_user(...)
--Jason
> + }
> +
> 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..aa76cb3f9107 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;
> + /**
> + * @binary_payload: A 64bit payload for binary syncobjs.
> + *
> + * We use the 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.
> + */
> + atomic64_t binary_payload;
> };
>
> void drm_syncobj_free(struct kref *kref);
> diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
> index 8a5b2f8f8eb9..78a0a413b788 100644
> --- a/include/uapi/drm/drm.h
> +++ b/include/uapi/drm/drm.h
> @@ -785,6 +785,22 @@ struct drm_syncobj_timeline_array {
> __u32 pad;
> };
>
> +struct drm_syncobj_binary_array {
> + /* A pointer to an array of u32 syncobj handles. */
> + __u64 handles;
> + /* A pointer to an array of u32 access flags for each handle. */
> + __u64 access_flags;
> + /* The binary value of a syncobj is read before it is incremented.
> */
> +#define DRM_SYNCOBJ_BINARY_VALUE_READ (1u << 0)
> +#define DRM_SYNCOBJ_BINARY_VALUE_INC (1u << 1)
> + /* A pointer to an array of u64 values written to by the kernel if
> the
> + * handle is flagged for reading.
> + */
> + __u64 values;
> + /* The length of the 3 arrays above. */
> + __u32 count_handles;
> + __u32 pad;
> +};
>
> /* Query current scanout sequence number */
> struct drm_crtc_get_sequence {
> @@ -946,6 +962,7 @@ 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_BINARY DRM_IOWR(0xCE, struct
> drm_syncobj_binary_array)
>
> /**
> * Device specific ioctls should only be in their respective headers
> --
> 2.23.0.rc1
>
>
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