[PATCH AUTOSEL 5.1 004/141] drm/virtio: set seqno for dma-fence

Sasha Levin
2019-07-19T04:03:05Z

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 d577cb76f5ad..eaa19c338f68 100644
--- a/drivers/gpu/drm/virtio/virtgpu_drv.h
+++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
@@ -85,7 +85,6 @@ 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 21bd4c4a32d1..216ab005e224 100644
--- a/drivers/gpu/drm/virtio/virtgpu_fence.c
+++ b/drivers/gpu/drm/virtio/virtgpu_fence.c
@@ -40,16 +40,14 @@ static bool virtio_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