[PATCH] drm/syncobj: add DRM_IOCTL_SYNCOBJ_IMPORT/EXPORT_SYNC_FILE
Erik Kurzinger
ekurzinger at nvidia.com
Thu Jul 20 17:40:08 UTC 2023
On 7/20/23 02:43, Simon Ser wrote:
> On Wednesday, July 19th, 2023 at 19:05, Erik Kurzinger <ekurzinger at nvidia.com> wrote:
>
>> These new ioctls perform a task similar to
>> DRM_IOCTL_SYNCOBJ_HANDLE_TO_FD/FD_TO_HANDLE with the
>> IMPORT/EXPORT_SYNC_FILE flag set, except that they allow specifying the
>> timeline point to import or export the fence to or from on a timeline
>> syncobj.
>>
>> This eliminates the need to use a temporary binary syncobj along with
>> DRM_IOCTL_SYNCOBJ_TRANSFER to achieve such a thing, which is the
>> technique userspace has had to employ up to this point. While that does
>> work, it is rather awkward from the programmer's perspective. Since DRM
>> syncobjs have been proposed as the basis for display server explicit
>> synchronization protocols, e.g. [1] and [2], providing a more
>> streamlined interface now seems worthwhile.
>
> This looks like a good idea to me! The patch looks good as well, apart
> from one tricky issue, see below...
>
>> [1] https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/90
>> [2] https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/967
>>
>> Accompanying userspace patches...
>> IGT: https://gitlab.freedesktop.org/ekurzinger/igt-gpu-tools/-/commit/241e7f379aeaa9b22a32277e77ad4011c8717a57
>> libdrm: https://gitlab.freedesktop.org/ekurzinger/drm/-/commit/b3961a592fc6f8b05f7e3a12413fb58eca2dbfa2
>
> (Unfortunately this isn't enough when it comes to user-space patches: the
> kernel rules require a "real" user of the new IOCTL, not just a libdr IOCTL
> wrapper. I will post a patch to make use of this from wlroots if that helps.)
>
Thanks for taking a look, Simon. If that's the case I could also update my Xwayland MR to use the new functions.
>> Signed-off-by: Erik Kurzinger <ekurzinger at nvidia.com>
>> ---
>> drivers/gpu/drm/drm_internal.h | 4 +++
>> drivers/gpu/drm/drm_ioctl.c | 4 +++
>> drivers/gpu/drm/drm_syncobj.c | 60 ++++++++++++++++++++++++++++++----
>> include/uapi/drm/drm.h | 9 +++++
>> 4 files changed, 71 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h
>> index d7e023bbb0d5..64a28ed26a16 100644
>> --- a/drivers/gpu/drm/drm_internal.h
>> +++ b/drivers/gpu/drm/drm_internal.h
>> @@ -253,6 +253,10 @@ 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_import_sync_file_ioctl(struct drm_device *dev, void *data,
>> + struct drm_file *file_private);
>> +int drm_syncobj_export_sync_file_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 7c9d66ee917d..0344e8e447bc 100644
>> --- a/drivers/gpu/drm/drm_ioctl.c
>> +++ b/drivers/gpu/drm/drm_ioctl.c
>> @@ -710,6 +710,10 @@ 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_IMPORT_SYNC_FILE, drm_syncobj_import_sync_file_ioctl,
>> + DRM_RENDER_ALLOW),
>> + DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_EXPORT_SYNC_FILE, drm_syncobj_export_sync_file_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 0c2be8360525..bf0c1eae353a 100644
>> --- a/drivers/gpu/drm/drm_syncobj.c
>> +++ b/drivers/gpu/drm/drm_syncobj.c
>> @@ -181,6 +181,13 @@
>> * Note that if you want to transfer a struct &dma_fence_chain from a given
>> * point on a timeline syncobj from/into a binary syncobj, you can use the
>> * point 0 to mean take/replace the fence in the syncobj.
>> + *
>> + * &DRM_IOCTL_SYNCOBJ_IMPORT_SYNC_FILE and &DRM_IOCTL_SYNCOBJ_EXPORT_SYNC_FILE
>> + * let the client import or export the struct &dma_fence_chain of a syncobj
>> + * at a particular timeline point from or to a sync file.
>> + * These behave similarly to &DRM_SYNCOBJ_FD_TO_HANDLE_FLAGS_IMPORT_SYNC_FILE
>> + * and &DRM_SYNCOBJ_HANDLE_TO_FD_FLAGS_EXPORT_SYNC_FILE described above, except
>> + * that they accommodate timeline syncobjs in addition to binary syncobjs.
>> */
>>
>> #include <linux/anon_inodes.h>
>> @@ -682,10 +689,11 @@ static int drm_syncobj_fd_to_handle(struct drm_file *file_private,
>> }
>>
>> static int drm_syncobj_import_sync_file_fence(struct drm_file *file_private,
>> - int fd, int handle)
>> + int fd, u64 point, int handle)
>
> Nit: can we specify the point after the handle, for consistency with
> drm_syncobj_export_sync_file()? It's pretty easy to mix up these two arguments.
>
>> {
>> struct dma_fence *fence = sync_file_get_fence(fd);
>> struct drm_syncobj *syncobj;
>> + int ret = 0;
>>
>> if (!fence)
>> return -EINVAL;
>> @@ -696,14 +704,23 @@ static int drm_syncobj_import_sync_file_fence(struct drm_file *file_private,
>> return -ENOENT;
>> }
>>
>> - drm_syncobj_replace_fence(syncobj, fence);
>> + if (point == 0) {
>> + drm_syncobj_replace_fence(syncobj, fence);
>> + } else {
>> + struct dma_fence_chain *chain = dma_fence_chain_alloc();
>> + if (chain) {
>> + drm_syncobj_add_point(syncobj, chain, fence, point);
>> + } else {
>> + ret = -ENOMEM;
>> + }
>> + }
>> dma_fence_put(fence);
>> drm_syncobj_put(syncobj);
>> - return 0;
>> + return ret;
>> }
>>
>> static int drm_syncobj_export_sync_file(struct drm_file *file_private,
>> - int handle, int *p_fd)
>> + int handle, u64 point, int *p_fd)
>> {
>> int ret;
>> struct dma_fence *fence;
>> @@ -713,7 +730,7 @@ static int drm_syncobj_export_sync_file(struct drm_file *file_private,
>> if (fd < 0)
>> return fd;
>>
>> - ret = drm_syncobj_find_fence(file_private, handle, 0, 0, &fence);
>> + ret = drm_syncobj_find_fence(file_private, handle, point, 0, &fence);
>> if (ret)
>> goto err_put_fd;
>>
>> @@ -823,7 +840,7 @@ drm_syncobj_handle_to_fd_ioctl(struct drm_device *dev, void *data,
>>
>> if (args->flags & DRM_SYNCOBJ_HANDLE_TO_FD_FLAGS_EXPORT_SYNC_FILE)
>> return drm_syncobj_export_sync_file(file_private, args->handle,
>> - &args->fd);
>> + 0 /* binary */, &args->fd);
>>
>> return drm_syncobj_handle_to_fd(file_private, args->handle,
>> &args->fd);
>> @@ -848,6 +865,7 @@ drm_syncobj_fd_to_handle_ioctl(struct drm_device *dev, void *data,
>> if (args->flags & DRM_SYNCOBJ_FD_TO_HANDLE_FLAGS_IMPORT_SYNC_FILE)
>> return drm_syncobj_import_sync_file_fence(file_private,
>> args->fd,
>> + 0 /* binary */,
>> args->handle);
>>
>> return drm_syncobj_fd_to_handle(file_private, args->fd,
>> @@ -1515,3 +1533,33 @@ int drm_syncobj_query_ioctl(struct drm_device *dev, void *data,
>>
>> return ret;
>> }
>> +
>> +int drm_syncobj_import_sync_file_ioctl(struct drm_device *dev, void *data,
>> + struct drm_file *file_private)
>> +{
>> + struct drm_syncobj_sync_file *args = data;
>> +
>> + if (!drm_core_check_feature(dev, args->point == 0 ?
>> + DRIVER_SYNCOBJ :
>> + DRIVER_SYNCOBJ_TIMELINE))
>> + return -EOPNOTSUPP;
>> +
>> + return drm_syncobj_import_sync_file_fence(file_private,
>> + args->fd,
>> + args->point,
>> + args->handle);
>> +}
>> +
>> +int drm_syncobj_export_sync_file_ioctl(struct drm_device *dev, void *data,
>> + struct drm_file *file_private)
>> +{
>> + struct drm_syncobj_sync_file *args = data;
>> +
>> + if (!drm_core_check_feature(dev, args->point == 0 ?
>> + DRIVER_SYNCOBJ :
>> + DRIVER_SYNCOBJ_TIMELINE))
>> + return -EOPNOTSUPP;
>> +
>> + return drm_syncobj_export_sync_file(file_private, args->handle,
>> + args->point, &args->fd);
>> +}
>> diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
>> index a87bbbbca2d4..e1f045011c22 100644
>> --- a/include/uapi/drm/drm.h
>> +++ b/include/uapi/drm/drm.h
>> @@ -884,6 +884,12 @@ struct drm_syncobj_transfer {
>> __u32 pad;
>> };
>>
>> +struct drm_syncobj_sync_file {
>> + __u32 handle;
>> + __u32 fd;
>> + __u64 point;
>> +};
>> +
>> #define DRM_SYNCOBJ_WAIT_FLAGS_WAIT_ALL (1 << 0)
>> #define DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT (1 << 1)
>> #define DRM_SYNCOBJ_WAIT_FLAGS_WAIT_AVAILABLE (1 << 2) /* wait for time point to become available */
>> @@ -1139,6 +1145,9 @@ extern "C" {
>> #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_IMPORT_SYNC_FILE DRM_IOWR(0xCE, struct drm_syncobj_sync_file)
>> +#define DRM_IOCTL_SYNCOBJ_EXPORT_SYNC_FILE DRM_IOWR(0xCF, struct drm_syncobj_sync_file)
>
> So, there is a footgun here, one that I hit myself with before: 0xCE is already
> used by DRM_IOCTL_MODE_GETFB2. And there is no check whatsoever about
> conflicting IOCTL numbers. The only reason I noticed is that I got some pretty
> weird behavior when trying to detect for the IOCTL availability in IGT, and
> someone from AMD noticed some GETFB2 IGT test breakage when trying my patches.
>
>> /**
>> * DRM_IOCTL_MODE_GETFB2 - Get framebuffer metadata.
>> *
>> --
>> 2.41.0
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