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Commit d1f0132e authored by Mark McLoughlin's avatar Mark McLoughlin Committed by Rusty Russell
Browse files

lguest: add support for indirect ring entries 



Support the VIRTIO_RING_F_INDIRECT_DESC feature.

This is a simple matter of changing the descriptor walking
code to operate on a struct vring_desc* and supplying it
with an indirect table if detected.

Signed-off-by: default avatarMark McLoughlin <markmc@redhat.com>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent b60da13f

Documentation/lguest/lguest.c

+29 −12
Original line number Diff line number Diff line
@@ -536,20 +536,21 @@ static void *_check_pointer(unsigned long addr, unsigned int size, 
/* Each buffer in the virtqueues is actually a chain of descriptors.  This

 * function returns the next descriptor in the chain, or vq->vring.num if we're

 * at the end. */

static unsigned next_desc(struct virtqueue *vq, unsigned int i)

static unsigned next_desc(struct vring_desc *desc,

			  unsigned int i, unsigned int max)

{

	unsigned int next;



	/* If this descriptor says it doesn't chain, we're done. */

	if (!(vq->vring.desc[i].flags & VRING_DESC_F_NEXT))

		return vq->vring.num;

	if (!(desc[i].flags & VRING_DESC_F_NEXT))

		return max;



	/* Check they're not leading us off end of descriptors. */

	next = vq->vring.desc[i].next;

	next = desc[i].next;

	/* Make sure compiler knows to grab that: we don't want it changing! */

	wmb();



	if (next >= vq->vring.num)

	if (next >= max)

		errx(1, "Desc next is %u", next);



	return next;
@@ -585,7 +586,8 @@ static unsigned wait_for_vq_desc(struct virtqueue *vq, 
				 struct iovec iov[],

				 unsigned int *out_num, unsigned int *in_num)

{

	unsigned int i, head;

	unsigned int i, head, max;

	struct vring_desc *desc;

	u16 last_avail = lg_last_avail(vq);



	while (last_avail == vq->vring.avail->idx) {
@@ -630,15 +632,28 @@ static unsigned wait_for_vq_desc(struct virtqueue *vq, 
	/* When we start there are none of either input nor output. */

	*out_num = *in_num = 0;



	max = vq->vring.num;

	desc = vq->vring.desc;

	i = head;



	/* If this is an indirect entry, then this buffer contains a descriptor

	 * table which we handle as if it's any normal descriptor chain. */

	if (desc[i].flags & VRING_DESC_F_INDIRECT) {

		if (desc[i].len % sizeof(struct vring_desc))

			errx(1, "Invalid size for indirect buffer table");



		max = desc[i].len / sizeof(struct vring_desc);

		desc = check_pointer(desc[i].addr, desc[i].len);

		i = 0;

	}



	do {

		/* Grab the first descriptor, and check it's OK. */

		iov[*out_num + *in_num].iov_len = vq->vring.desc[i].len;

		iov[*out_num + *in_num].iov_len = desc[i].len;

		iov[*out_num + *in_num].iov_base

			= check_pointer(vq->vring.desc[i].addr,

					vq->vring.desc[i].len);

			= check_pointer(desc[i].addr, desc[i].len);

		/* If this is an input descriptor, increment that count. */

		if (vq->vring.desc[i].flags & VRING_DESC_F_WRITE)

		if (desc[i].flags & VRING_DESC_F_WRITE)

			(*in_num)++;

		else {

			/* If it's an output descriptor, they're all supposed
@@ -649,9 +664,9 @@ static unsigned wait_for_vq_desc(struct virtqueue *vq, 
		}



		/* If we've got too many, that implies a descriptor loop. */

		if (*out_num + *in_num > vq->vring.num)

		if (*out_num + *in_num > max)

			errx(1, "Looped descriptor");

	} while ((i = next_desc(vq, i)) != vq->vring.num);

	} while ((i = next_desc(desc, i, max)) != max);



	return head;

}
@@ -1331,6 +1346,8 @@ static void setup_tun_net(char *arg) 
	add_feature(dev, VIRTIO_NET_F_HOST_TSO4);

	add_feature(dev, VIRTIO_NET_F_HOST_TSO6);

	add_feature(dev, VIRTIO_NET_F_HOST_ECN);

	/* We handle indirect ring entries */

	add_feature(dev, VIRTIO_RING_F_INDIRECT_DESC);

	set_config(dev, sizeof(conf), &conf);



	/* We don't need the socket any more; setup is done. */