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    Subject[PATCH AUTOSEL 5.2 005/171] drm/virtio: set seqno for dma-fence
    Date
    From: Chia-I Wu <olvaffe@gmail.com>

    [ Upstream commit efe2bf965522bf0796d413b47a2abbf81d471d6f ]

    This is motivated by having meaningful ftrace events, but it also
    fixes use cases where dma_fence_is_later is called, such as in
    sync_file_merge.

    In other drivers, fence creation and cmdbuf submission normally
    happen atomically,

    mutex_lock();
    fence = dma_fence_create(..., ++timeline->seqno);
    submit_cmdbuf();
    mutex_unlock();

    and have no such issue. But in our driver, because most ioctls
    queue commands into ctrlq, we do not want to grab a lock. Instead,
    we set seqno to 0 when a fence is created, and update it when the
    command is finally queued and the seqno is known.

    Signed-off-by: Chia-I Wu <olvaffe@gmail.com>
    Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
    Link: http://patchwork.freedesktop.org/patch/msgid/20190429220825.156644-1-olvaffe@gmail.com
    Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/gpu/drm/virtio/virtgpu_drv.h | 1 -
    drivers/gpu/drm/virtio/virtgpu_fence.c | 17 ++++++++++-------
    2 files changed, 10 insertions(+), 8 deletions(-)

    diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h
    index b69ae10ca238..d724fb3de44e 100644
    --- a/drivers/gpu/drm/virtio/virtgpu_drv.h
    +++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
    @@ -102,7 +102,6 @@ struct virtio_gpu_fence {
    struct dma_fence f;
    struct virtio_gpu_fence_driver *drv;
    struct list_head node;
    - uint64_t seq;
    };
    #define to_virtio_fence(x) \
    container_of(x, struct virtio_gpu_fence, f)
    diff --git a/drivers/gpu/drm/virtio/virtgpu_fence.c b/drivers/gpu/drm/virtio/virtgpu_fence.c
    index 87d1966192f4..72b4f7561432 100644
    --- a/drivers/gpu/drm/virtio/virtgpu_fence.c
    +++ b/drivers/gpu/drm/virtio/virtgpu_fence.c
    @@ -40,16 +40,14 @@ bool virtio_fence_signaled(struct dma_fence *f)
    {
    struct virtio_gpu_fence *fence = to_virtio_fence(f);

    - if (atomic64_read(&fence->drv->last_seq) >= fence->seq)
    + if (atomic64_read(&fence->drv->last_seq) >= fence->f.seqno)
    return true;
    return false;
    }

    static void virtio_fence_value_str(struct dma_fence *f, char *str, int size)
    {
    - struct virtio_gpu_fence *fence = to_virtio_fence(f);
    -
    - snprintf(str, size, "%llu", fence->seq);
    + snprintf(str, size, "%llu", f->seqno);
    }

    static void virtio_timeline_value_str(struct dma_fence *f, char *str, int size)
    @@ -76,6 +74,11 @@ struct virtio_gpu_fence *virtio_gpu_fence_alloc(struct virtio_gpu_device *vgdev)
    return fence;

    fence->drv = drv;
    +
    + /* This only partially initializes the fence because the seqno is
    + * unknown yet. The fence must not be used outside of the driver
    + * until virtio_gpu_fence_emit is called.
    + */
    dma_fence_init(&fence->f, &virtio_fence_ops, &drv->lock, drv->context, 0);

    return fence;
    @@ -89,13 +92,13 @@ int virtio_gpu_fence_emit(struct virtio_gpu_device *vgdev,
    unsigned long irq_flags;

    spin_lock_irqsave(&drv->lock, irq_flags);
    - fence->seq = ++drv->sync_seq;
    + fence->f.seqno = ++drv->sync_seq;
    dma_fence_get(&fence->f);
    list_add_tail(&fence->node, &drv->fences);
    spin_unlock_irqrestore(&drv->lock, irq_flags);

    cmd_hdr->flags |= cpu_to_le32(VIRTIO_GPU_FLAG_FENCE);
    - cmd_hdr->fence_id = cpu_to_le64(fence->seq);
    + cmd_hdr->fence_id = cpu_to_le64(fence->f.seqno);
    return 0;
    }

    @@ -109,7 +112,7 @@ void virtio_gpu_fence_event_process(struct virtio_gpu_device *vgdev,
    spin_lock_irqsave(&drv->lock, irq_flags);
    atomic64_set(&vgdev->fence_drv.last_seq, last_seq);
    list_for_each_entry_safe(fence, tmp, &drv->fences, node) {
    - if (last_seq < fence->seq)
    + if (last_seq < fence->f.seqno)
    continue;
    dma_fence_signal_locked(&fence->f);
    list_del(&fence->node);
    --
    2.20.1
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