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Subject[RFC PATCH] vhost: cache avail index in vhost_enable_notify()
Date
In vhost_enable_notify() we enable the notifications and we read
the avail index to check if new buffers have become available in
the meantime. In this case, the device would go to re-read avail
index to access the descriptor.

As we already do in other place, we can cache the value in `avail_idx`
and compare it with `last_avail_idx` to check if there are new
buffers available.

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
drivers/vhost/vhost.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 59edb5a1ffe2..07363dff559e 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -2543,8 +2543,9 @@ bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
&vq->avail->idx, r);
return false;
}
+ vq->avail_idx = vhost16_to_cpu(vq, avail_idx);

- return vhost16_to_cpu(vq, avail_idx) != vq->avail_idx;
+ return vq->avail_idx != vq->last_avail_idx;
}
EXPORT_SYMBOL_GPL(vhost_enable_notify);

--
2.31.1
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