[dpdk-stable] patch 'vhost: fix Windows VM hang' has been queued to stable release 16.07.2

[Yuanhan Liu]

Hi,

FYI, your patch has been queued to stable release 16.07.2

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable
yet. It will be pushed if I get no objections before 11/06/16.
So please shout if anyone has objections.

Thanks.

	--yliu

---
>From d904373cd8c4f017cb25c19b16a6c36a902de984 Mon Sep 17 00:00:00 2001
From: Zhihong Wang <zhihong.wang at intel.com>
Date: Mon, 19 Sep 2016 22:00:12 -0400
Subject: [PATCH] vhost: fix Windows VM hang

[ backported from upstream commit f46f6551436a5a7c8509a4cbade1a7fda39905b3 ]

This patch fixes a Windows VM compatibility issue in DPDK 16.07 vhost code
which causes the guest to hang once any packets are enqueued when mrg_rxbuf
is turned on by setting the right id and len in the used ring.

As defined in virtio spec 0.95 and 1.0, in each used ring element, id means
index of start of used descriptor chain, and len means total length of the
descriptor chain which was written to. While in 16.07 code, index of the
last descriptor is assigned to id, and the length of the last descriptor is
assigned to len.

How to test?

 1. Start testpmd in the host with a vhost port.

 2. Start a Windows VM image with qemu and connect to the vhost port.

 3. Start io forwarding with tx_first in host testpmd.

For 16.07 code, the Windows VM will hang once any packets are enqueued.

Signed-off-by: Zhihong Wang <zhihong.wang at intel.com>
Acked-by: Yuanhan Liu <yuanhan.liu at linux.intel.com>
---
 lib/librte_vhost/vhost_rxtx.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
index 08a73fd..5806f99 100644
--- a/lib/librte_vhost/vhost_rxtx.c
+++ b/lib/librte_vhost/vhost_rxtx.c
@@ -384,6 +384,8 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq,
 	uint16_t start_idx = vq->last_used_idx;
 	uint16_t cur_idx = start_idx;
 	uint64_t desc_addr;
+	uint32_t desc_chain_head;
+	uint32_t desc_chain_len;
 	uint32_t mbuf_offset, mbuf_avail;
 	uint32_t desc_offset, desc_avail;
 	uint32_t cpy_len;
@@ -412,6 +414,8 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq,
 
 	desc_avail  = buf_vec[vec_idx].buf_len - dev->vhost_hlen;
 	desc_offset = dev->vhost_hlen;
+	desc_chain_head = buf_vec[vec_idx].desc_idx;
+	desc_chain_len = desc_offset;
 
 	mbuf_avail  = rte_pktmbuf_data_len(m);
 	mbuf_offset = 0;
@@ -419,19 +423,21 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq,
 		/* done with current desc buf, get the next one */
 		if (desc_avail == 0) {
 			desc_idx = buf_vec[vec_idx].desc_idx;
+			vec_idx++;
 
 			if (!(vq->desc[desc_idx].flags & VRING_DESC_F_NEXT)) {
 				/* Update used ring with desc information */
 				used_idx = cur_idx++ & (vq->size - 1);
-				vq->used->ring[used_idx].id  = desc_idx;
-				vq->used->ring[used_idx].len = desc_offset;
+				vq->used->ring[used_idx].id = desc_chain_head;
+				vq->used->ring[used_idx].len = desc_chain_len;
 				vhost_log_used_vring(dev, vq,
 					offsetof(struct vring_used,
 						 ring[used_idx]),
 					sizeof(vq->used->ring[used_idx]));
+				desc_chain_head = buf_vec[vec_idx].desc_idx;
+				desc_chain_len = 0;
 			}
 
-			vec_idx++;
 			desc_addr = gpa_to_vva(dev, buf_vec[vec_idx].buf_addr);
 			if (unlikely(!desc_addr))
 				return 0;
@@ -463,11 +469,12 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq,
 		mbuf_offset += cpy_len;
 		desc_avail  -= cpy_len;
 		desc_offset += cpy_len;
+		desc_chain_len += cpy_len;
 	}
 
 	used_idx = cur_idx & (vq->size - 1);
-	vq->used->ring[used_idx].id = buf_vec[vec_idx].desc_idx;
-	vq->used->ring[used_idx].len = desc_offset;
+	vq->used->ring[used_idx].id = desc_chain_head;
+	vq->used->ring[used_idx].len = desc_chain_len;
 	vhost_log_used_vring(dev, vq,
 		offsetof(struct vring_used, ring[used_idx]),
 		sizeof(vq->used->ring[used_idx]));
-- 
1.9.0