lguest: add support for indirect ring entries (d1f0132e) · Commits · 戴 / test

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. */

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