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From: Xueming Li <xuemingl@nvidia.com>
To: <qemu-devel@nongnu.org>
Cc: <xuemingl@nvidia.com>, <qemu-stable@nongnu.org>,
	<tiwei.bie@intel.com>,
	Yuwei Zhang <zhangyuwei.9149@bytedance.com>,
	"Michael S. Tsirkin" <mst@redhat.com>
Subject: [PATCH v2 1/2] vhost-user: fix VirtQ notifier cleanup
Date: Fri, 17 Sep 2021 20:26:15 +0800	[thread overview]
Message-ID: <20210917122616.6067-2-xuemingl@nvidia.com> (raw)
In-Reply-To: <20210917122616.6067-1-xuemingl@nvidia.com>

When vhost-user device stop and unmmap notifier address, vCPU thread
that writing the notifier via old flatview failed with accessing invalid
address.

To avoid this concurrent issue, wait memory flatview update by draining
rcu callbacks before unmaping notifiers.

Fixes: 44866521bd6e ("vhost-user: support registering external host notifiers")
Cc: tiwei.bie@intel.com
Cc: qemu-stable@nongnu.org
Cc: Yuwei Zhang <zhangyuwei.9149@bytedance.com>
Signed-off-by: Xueming Li <xuemingl@nvidia.com>
---
 hw/virtio/vhost-user.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 2c8556237f..08581e6711 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -1165,6 +1165,11 @@ static void vhost_user_host_notifier_remove(struct vhost_dev *dev,
 
     if (n->addr && n->set) {
         virtio_queue_set_host_notifier_mr(vdev, queue_idx, &n->mr, false);
+        if (!qemu_in_vcpu_thread())
+            /* Wait vCPU threads accessing notifier via old flatview. */
+            drain_call_rcu();
+        munmap(n->addr, qemu_real_host_page_size);
+        n->addr = NULL;
         n->set = false;
     }
 }
@@ -1502,12 +1507,7 @@ static int vhost_user_slave_handle_vring_host_notifier(struct vhost_dev *dev,
 
     n = &user->notifier[queue_idx];
 
-    if (n->addr) {
-        virtio_queue_set_host_notifier_mr(vdev, queue_idx, &n->mr, false);
-        object_unparent(OBJECT(&n->mr));
-        munmap(n->addr, page_size);
-        n->addr = NULL;
-    }
+    vhost_user_host_notifier_remove(dev, queue_idx);
 
     if (area->u64 & VHOST_USER_VRING_NOFD_MASK) {
         return 0;
@@ -2484,11 +2484,17 @@ void vhost_user_cleanup(VhostUserState *user)
     for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
         if (user->notifier[i].addr) {
             object_unparent(OBJECT(&user->notifier[i].mr));
+        }
+    }
+    memory_region_transaction_commit();
+    /* Wait VM threads accessing old flatview which contains notifier. */
+    drain_call_rcu();
+    for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
+        if (user->notifier[i].addr) {
             munmap(user->notifier[i].addr, qemu_real_host_page_size);
             user->notifier[i].addr = NULL;
         }
     }
-    memory_region_transaction_commit();
     user->chr = NULL;
 }
 
-- 
2.33.0



  reply	other threads:[~2021-09-17 12:28 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-12 16:20 [PATCH 0/2] Improve vhost-user VQ notifier unmap Xueming Li
2021-09-12 16:20 ` [PATCH 1/2] vhost-user: fix VirtQ notifier cleanup Xueming Li
2021-09-14  8:42   ` Xueming(Steven) Li
2021-09-12 16:20 ` [PATCH 2/2] vhost-user: remove VirtQ notifier restore Xueming Li
2021-09-17 12:26 ` [PATCH v2 0/2] Improve vhost-user VQ notifier unmap Xueming Li
2021-09-17 12:26   ` Xueming Li [this message]
2021-10-05 14:40     ` [PATCH v2 1/2] vhost-user: fix VirtQ notifier cleanup Michael S. Tsirkin
2021-10-08  8:00       ` Xueming(Steven) Li
2021-09-17 12:26   ` [PATCH v2 2/2] vhost-user: remove VirtQ notifier restore Xueming Li

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