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vhost_net: fix assertion triggered by batch of host notifiers processing 

When the backend of vhost_net restarts during the vm is running, vhost_net
is stopped and started. The virtio_device_grab_ioeventfd() fucntion in
vhost_net_enable_notifiers() will result in a call to
virtio_bus_set_host_notifier()(assign=false).

And now virtio_device_grab_ioeventfd() is batched in a single transaction
with virtio_bus_set_host_notifier()(assign=true).

This triggers the following assertion:

kvm_mem_ioeventfd_del: error deleting ioeventfd: Bad file descriptor

This patch moves virtio_device_grab_ioeventfd() out of the batch to fix
this problem.

To be noted that the for loop to release ioeventfd should start from i+1,
not i, because the i-th ioeventfd has already been released in
vhost_dev_disable_notifiers_nvqs().

Fixes: 6166799f6 ("vhost_net: configure all host notifiers in a single MR transaction")
Signed-off-by: Zuo Boqun <zuoboqun@baidu.com>
Reported-by: Gao Shiyuan <gaoshiyuan@baidu.com>

Message-Id: <20241115080312.3184-1-zuoboqun@baidu.com>
Acked-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
zuoboqun 2024-11-15 16:03:12 +08:00 committed by Michael S. Tsirkin
parent 34754a3a62
commit 16f6804c46
1 changed files with 24 additions and 11 deletions
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35
hw/net/vhost_net.c
View File

@ -229,9 +229,24 @@ static int vhost_net_enable_notifiers(VirtIODevice *dev,
int nvhosts = data_queue_pairs + cvq;
struct vhost_net *net;
struct vhost_dev *hdev;
int r, i, j;
int r, i, j, k;
NetClientState *peer;
/*
* We will pass the notifiers to the kernel, make sure that QEMU
* doesn't interfere.
*/
for (i = 0; i < nvhosts; i++) {
r = virtio_device_grab_ioeventfd(dev);
if (r < 0) {
error_report("vhost %d binding does not support host notifiers", i);
for (k = 0; k < i; k++) {
virtio_device_release_ioeventfd(dev);
}
return r;
}
}
/*
* Batch all the host notifiers in a single transaction to avoid
* quadratic time complexity in address_space_update_ioeventfds().
@ -247,16 +262,6 @@ static int vhost_net_enable_notifiers(VirtIODevice *dev,
net = get_vhost_net(peer);
hdev = &net->dev;
/*
* We will pass the notifiers to the kernel, make sure that QEMU
* doesn't interfere.
*/
r = virtio_device_grab_ioeventfd(dev);
if (r < 0) {
error_report("binding does not support host notifiers");
memory_region_transaction_commit();
goto fail_nvhosts;
}
for (j = 0; j < hdev->nvqs; j++) {
r = virtio_bus_set_host_notifier(VIRTIO_BUS(qbus),
@ -277,6 +282,14 @@ static int vhost_net_enable_notifiers(VirtIODevice *dev,
return 0;
fail_nvhosts:
vhost_net_disable_notifiers_nvhosts(dev, ncs, data_queue_pairs, i);
/*
* This for loop starts from i+1, not i, because the i-th ioeventfd
* has already been released in vhost_dev_disable_notifiers_nvqs().
*/
for (k = i + 1; k < nvhosts; k++) {
virtio_device_release_ioeventfd(dev);
}
return r;
}