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Commit e93300b1 authored by Rusty Russell's avatar Rusty Russell
Browse files

virtio: add debugging if driver doesn't kick. 



Under the existing #ifdef DEBUG, check that they don't have more than
1/10 of a second between an add_buf() and a
virtqueue_notify()/virtqueue_kick_prepare() call.

We could get false positives on a really busy system, but good for
development.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent ee7cd898

drivers/virtio/virtio_ring.c

+31 −0
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ 
#include <linux/device.h>

#include <linux/slab.h>

#include <linux/module.h>

#include <linux/hrtimer.h>



/* virtio guest is communicating with a virtual "device" that actually runs on

 * a host processor.  Memory barriers are used to control SMP effects. */
@@ -108,6 +109,10 @@ struct vring_virtqueue 
#ifdef DEBUG

	/* They're supposed to lock for us. */

	unsigned int in_use;



	/* Figure out if their kicks are too delayed. */

	bool last_add_time_valid;

	ktime_t last_add_time;

#endif



	/* Tokens for callbacks. */
@@ -198,6 +203,19 @@ int virtqueue_add_buf(struct virtqueue *_vq, 


	BUG_ON(data == NULL);



#ifdef DEBUG

	{

		ktime_t now = ktime_get();



		/* No kick or get, with .1 second between?  Warn. */

		if (vq->last_add_time_valid)

			WARN_ON(ktime_to_ms(ktime_sub(now, vq->last_add_time))

					    > 100);

		vq->last_add_time = now;

		vq->last_add_time_valid = true;

	}

#endif



	/* If the host supports indirect descriptor tables, and we have multiple

	 * buffers, then go indirect. FIXME: tune this threshold */

	if (vq->indirect && (out + in) > 1 && vq->num_free) {
@@ -298,6 +316,14 @@ bool virtqueue_kick_prepare(struct virtqueue *_vq) 
	new = vq->vring.avail->idx;

	vq->num_added = 0;



#ifdef DEBUG

	if (vq->last_add_time_valid) {

		WARN_ON(ktime_to_ms(ktime_sub(ktime_get(),

					      vq->last_add_time)) > 100);

	}

	vq->last_add_time_valid = false;

#endif



	if (vq->event) {

		needs_kick = vring_need_event(vring_avail_event(&vq->vring),

					      new, old);
@@ -435,6 +461,10 @@ void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len) 
		virtio_mb(vq);

	}



#ifdef DEBUG

	vq->last_add_time_valid = false;

#endif



	END_USE(vq);

	return ret;

}
@@ -620,6 +650,7 @@ struct virtqueue *vring_new_virtqueue(unsigned int num, 
	list_add_tail(&vq->vq.list, &vdev->vqs);

#ifdef DEBUG

	vq->in_use = false;

	vq->last_add_time_valid = false;

#endif



	vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC);