patch 'vhost: fix deadlock during vDPA SW live migration' has been queued to stable release 22.11.5

[luca.boccassi at gmail.com]

Hi,

FYI, your patch has been queued to stable release 22.11.5

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 03/09/24. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the
patch applied to the branch. This will indicate if there was any rebasing
needed to apply to the stable branch. If there were code changes for rebasing
(ie: not only metadata diffs), please double check that the rebase was
correctly done.

Queued patches are on a temporary branch at:
https://github.com/bluca/dpdk-stable

This queued commit can be viewed at:
https://github.com/bluca/dpdk-stable/commit/9b6bdd022bf51267805e5e252545979387be3f4d

Thanks.

Luca Boccassi

---
>From 9b6bdd022bf51267805e5e252545979387be3f4d Mon Sep 17 00:00:00 2001
From: Hao Chen <chenh at yusur.tech>
Date: Mon, 22 Jan 2024 11:27:44 +0800
Subject: [PATCH] vhost: fix deadlock during vDPA SW live migration

[ upstream commit 19639c3b693bcfdc941c56d9d5bd60f65a8eeecb ]

In a nested virtualization environment, running dpdk-vdpa
in QEMU-L1 for software live migration will result in a
deadlock between dpdk-vdpa and QEMU-L2 processes.
'rte_vdpa_relay_vring_used'->
'__vhost_iova_to_vva'->
'vhost_user_iotlb_rd_unlock(vq)'->
'vhost_user_iotlb_miss'-> send vhost message
'VHOST_USER_SLAVE_IOTLB_MSG' to QEMU-L2's vdpa socket, then
call 'vhost_user_iotlb_rd_lock(vq)' to hold the read lock
`iotlb_lock`.

But there is no place to release this read lock.

QEMU-L2 get the 'VHOST_USER_SLAVE_IOTLB_MSG', then call
'vhost_user_send_device_iotlb_msg' to send
'VHOST_USER_IOTLB_MSG' messages to dpdk-vdpa.

dpdk-vdpa will call vhost_user_iotlb_cache_insert and will
obtain the write lock `iotlb_lock`, but the read lock
`iotlb_lock` has not been released and will block here.

This patch add lock and unlock function to fix the deadlock.

Fixes: b13ad2decc83 ("vhost: provide helpers for virtio ring relay")

Signed-off-by: Hao Chen <chenh at yusur.tech>
Reviewed-by: Maxime Coquelin <maxime.coquelin at redhat.com>
---
 lib/vhost/vdpa.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/lib/vhost/vdpa.c b/lib/vhost/vdpa.c
index 577cb00a43..cf51ca957a 100644
--- a/lib/vhost/vdpa.c
+++ b/lib/vhost/vdpa.c
@@ -19,6 +19,7 @@
 #include "rte_vdpa.h"
 #include "vdpa_driver.h"
 #include "vhost.h"
+#include "iotlb.h"
 
 /** Double linked list of vDPA devices. */
 TAILQ_HEAD(vdpa_device_list, rte_vdpa_device);
@@ -191,17 +192,21 @@ rte_vdpa_relay_vring_used(int vid, uint16_t qid, void *vring_m)
 			if (unlikely(nr_descs > vq->size))
 				return -1;
 
+			vhost_user_iotlb_rd_lock(vq);
 			desc_ring = (struct vring_desc *)(uintptr_t)
 				vhost_iova_to_vva(dev, vq,
 						vq->desc[desc_id].addr, &dlen,
 						VHOST_ACCESS_RO);
+			vhost_user_iotlb_rd_unlock(vq);
 			if (unlikely(!desc_ring))
 				return -1;
 
 			if (unlikely(dlen < vq->desc[desc_id].len)) {
+				vhost_user_iotlb_rd_lock(vq);
 				idesc = vhost_alloc_copy_ind_table(dev, vq,
 						vq->desc[desc_id].addr,
 						vq->desc[desc_id].len);
+				vhost_user_iotlb_rd_unlock(vq);
 				if (unlikely(!idesc))
 					return -1;
 
@@ -218,9 +223,12 @@ rte_vdpa_relay_vring_used(int vid, uint16_t qid, void *vring_m)
 			if (unlikely(nr_descs-- == 0))
 				goto fail;
 			desc = desc_ring[desc_id];
-			if (desc.flags & VRING_DESC_F_WRITE)
+			if (desc.flags & VRING_DESC_F_WRITE) {
+				vhost_user_iotlb_rd_lock(vq);
 				vhost_log_write_iova(dev, vq, desc.addr,
 						     desc.len);
+				vhost_user_iotlb_rd_unlock(vq);
+			}
 			desc_id = desc.next;
 		} while (desc.flags & VRING_DESC_F_NEXT);
 
-- 
2.39.2

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2024-03-07 01:05:38.869547086 +0000
+++ 0046-vhost-fix-deadlock-during-vDPA-SW-live-migration.patch	2024-03-07 01:05:34.786939762 +0000
@@ -1 +1 @@
-From 19639c3b693bcfdc941c56d9d5bd60f65a8eeecb Mon Sep 17 00:00:00 2001
+From 9b6bdd022bf51267805e5e252545979387be3f4d Mon Sep 17 00:00:00 2001
@@ -5,0 +6,2 @@
+[ upstream commit 19639c3b693bcfdc941c56d9d5bd60f65a8eeecb ]
+
@@ -30 +31,0 @@
-Cc: stable at dpdk.org
@@ -35,2 +36,2 @@
- lib/vhost/vdpa.c | 11 +++++++++--
- 1 file changed, 9 insertions(+), 2 deletions(-)
+ lib/vhost/vdpa.c | 10 +++++++++-
+ 1 file changed, 9 insertions(+), 1 deletion(-)
@@ -39 +40 @@
-index 9776fc07a9..a1dd5a753b 100644
+index 577cb00a43..cf51ca957a 100644
@@ -50,9 +51 @@
-@@ -147,7 +148,6 @@ rte_vdpa_unregister_device(struct rte_vdpa_device *dev)
- 
- int
- rte_vdpa_relay_vring_used(int vid, uint16_t qid, void *vring_m)
--	__rte_no_thread_safety_analysis /* FIXME: requires iotlb_lock? */
- {
- 	struct virtio_net *dev = get_device(vid);
- 	uint16_t idx, idx_m, desc_id;
-@@ -193,17 +193,21 @@ rte_vdpa_relay_vring_used(int vid, uint16_t qid, void *vring_m)
+@@ -191,17 +192,21 @@ rte_vdpa_relay_vring_used(int vid, uint16_t qid, void *vring_m)
@@ -80 +73 @@
-@@ -220,9 +224,12 @@ rte_vdpa_relay_vring_used(int vid, uint16_t qid, void *vring_m)
+@@ -218,9 +223,12 @@ rte_vdpa_relay_vring_used(int vid, uint16_t qid, void *vring_m)