Re: [PATCH v3 1/1] drm/syncobj: add sideband payload

[Chunming Zhou <zhoucm1@amd.com>]

No, I just see your comment "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. ".

In that, you mentioned wait for sideband.
So I want to know we how to use that, maybe I miss something in previous 
discussing thread.

-DAvid


在 2019/8/8 21:38, Lionel Landwerlin 写道:
> Interesting question :)
>
> I didn't see any usecase for that.
> This sideband payload value is used for a wait so waiting on the wait 
> value for another wait is bit meta :)
>
> Do you have a use case for that?
>
> -Lionel
>
> On 08/08/2019 16:23, Chunming Zhou wrote:
>> The propursal is fine with me.
>>
>> one question:
>>
>> how to wait sideband payload? Following patch will show that?
>>
>> -David
>>
>> 在 2019/8/8 21:14, Lionel Landwerlin 写道:
>>> 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)
>>>
>>> Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
>>> Cc: Christian Koenig <Christian.Koenig@amd.com>
>>> Cc: Jason Ekstrand <jason@jlekstrand.net>
>>> Cc: David(ChunMing) Zhou <David1.Zhou@amd.com>
>>> ---
>>>    drivers/gpu/drm/drm_internal.h |  4 ++
>>>    drivers/gpu/drm/drm_ioctl.c    |  5 +++
>>>    drivers/gpu/drm/drm_syncobj.c  | 79 
>>> +++++++++++++++++++++++++++++++++-
>>>    include/drm/drm_syncobj.h      |  9 ++++
>>>    include/uapi/drm/drm.h         |  2 +
>>>    5 files changed, 98 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/drm_internal.h 
>>> b/drivers/gpu/drm/drm_internal.h
>>> index 51a2055c8f18..0c9736199df0 100644
>>> --- a/drivers/gpu/drm/drm_internal.h
>>> +++ b/drivers/gpu/drm/drm_internal.h
>>> @@ -208,6 +208,10 @@ 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_get_sideband_ioctl(struct drm_device *dev, void *data,
>>> +                   struct drm_file *file_private);
>>> +int drm_syncobj_set_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..48500bf62801 100644
>>> --- a/drivers/gpu/drm/drm_ioctl.c
>>> +++ b/drivers/gpu/drm/drm_ioctl.c
>>> @@ -703,6 +703,11 @@ 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_GET_SIDEBAND, 
>>> drm_syncobj_get_sideband_ioctl,
>>> +              DRM_RENDER_ALLOW),
>>> +    DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_SET_SIDEBAND, 
>>> drm_syncobj_set_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..c90ef20b9242 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);
>>>    @@ -1321,6 +1323,81 @@ 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_get_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->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++) {
>>> +        copy_to_user(&points[i], &syncobjs[i]->sideband_payload, 
>>> sizeof(uint64_t));
>>> +        ret = ret ? -EFAULT : 0;
>>> +        if (ret)
>>> +            break;
>>> +    }
>>> +
>>> +    drm_syncobj_array_free(syncobjs, args->count_handles);
>>> +
>>> +    return ret;
>>> +}
>>> +
>>> +int drm_syncobj_set_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->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++) {
>>> +        copy_from_user(&syncobjs[i]->sideband_payload, &points[i], 
>>> sizeof(uint64_t));
>>> +        ret = ret ? -EFAULT : 0;
>>> +        if (ret)
>>> +            break;
>>> +    }
>>> +
>>>        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..cffdc6c9772c 100644
>>> --- a/include/uapi/drm/drm.h
>>> +++ b/include/uapi/drm/drm.h
>>> @@ -946,6 +946,8 @@ 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_GET_SIDEBAND    DRM_IOR(0xCE, struct 
>>> drm_syncobj_timeline_array)
>>> +#define DRM_IOCTL_SYNCOBJ_SET_SIDEBAND    DRM_IOWR(0xCF, struct 
>>> drm_syncobj_timeline_array)
>>>       /**
>>>     * Device specific ioctls should only be in their respective headers
>
>
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