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Commit c49e4e57 authored by Jason Wang's avatar Jason Wang Committed by David S. Miller
Browse files

vhost: switch to use vhost_add_used_n() 



Let vhost_add_used() to use vhost_add_used_n() to reduce the code
duplication. To avoid the overhead brought by __copy_to_user(). We will use
put_user() when one used need to be added.

Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c92112ae

drivers/vhost/vhost.c

+12 −42
Original line number Diff line number Diff line
@@ -1332,48 +1332,9 @@ EXPORT_SYMBOL_GPL(vhost_discard_vq_desc); 
 * want to notify the guest, using eventfd. */

int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)

{

	struct vring_used_elem __user *used;

	struct vring_used_elem heads = { head, len };



	/* The virtqueue contains a ring of used buffers.  Get a pointer to the

	 * next entry in that used ring. */

	used = &vq->used->ring[vq->last_used_idx % vq->num];

	if (__put_user(head, &used->id)) {

		vq_err(vq, "Failed to write used id");

		return -EFAULT;

	}

	if (__put_user(len, &used->len)) {

		vq_err(vq, "Failed to write used len");

		return -EFAULT;

	}

	/* Make sure buffer is written before we update index. */

	smp_wmb();

	if (__put_user(vq->last_used_idx + 1, &vq->used->idx)) {

		vq_err(vq, "Failed to increment used idx");

		return -EFAULT;

	}

	if (unlikely(vq->log_used)) {

		/* Make sure data is seen before log. */

		smp_wmb();

		/* Log used ring entry write. */

		log_write(vq->log_base,

			  vq->log_addr +

			   ((void __user *)used - (void __user *)vq->used),

			  sizeof *used);

		/* Log used index update. */

		log_write(vq->log_base,

			  vq->log_addr + offsetof(struct vring_used, idx),

			  sizeof vq->used->idx);

		if (vq->log_ctx)

			eventfd_signal(vq->log_ctx, 1);

	}

	vq->last_used_idx++;

	/* If the driver never bothers to signal in a very long while,

	 * used index might wrap around. If that happens, invalidate

	 * signalled_used index we stored. TODO: make sure driver

	 * signals at least once in 2^16 and remove this. */

	if (unlikely(vq->last_used_idx == vq->signalled_used))

		vq->signalled_used_valid = false;

	return 0;

	return vhost_add_used_n(vq, &heads, 1);

}

EXPORT_SYMBOL_GPL(vhost_add_used);
@@ -1387,7 +1348,16 @@ static int __vhost_add_used_n(struct vhost_virtqueue *vq, 


	start = vq->last_used_idx % vq->num;

	used = vq->used->ring + start;

	if (__copy_to_user(used, heads, count * sizeof *used)) {

	if (count == 1) {

		if (__put_user(heads[0].id, &used->id)) {

			vq_err(vq, "Failed to write used id");

			return -EFAULT;

		}

		if (__put_user(heads[0].len, &used->len)) {

			vq_err(vq, "Failed to write used len");

			return -EFAULT;

		}

	} else if (__copy_to_user(used, heads, count * sizeof *used)) {

		vq_err(vq, "Failed to write used");

		return -EFAULT;

	}