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vhost: prevent features to be changed while device is running

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As section 2.2 of the Virtio spec states about features
negotiation:
"During device initialization, the driver reads this and tells
the device the subset that it accepts. The only way to
renegotiate is to reset the device."

This patch implements a check to prevent illegal features change
while the device is running.

One exception is the VHOST_F_LOG_ALL feature bit, which is enabled
when live-migration is initiated. But this feature is not negotiated
with the Virtio driver, but directly with the Vhost master.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Acked-by: Yuanhan Liu <yliu@fridaylinux.org>
This commit is contained in:
Maxime Coquelin 2017-12-13 09:51:06 +01:00 committed by Ferruh Yigit
parent 6d18505efa
commit 07f8db29b8
1 changed files with 16 additions and 1 deletions
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17
lib/librte_vhost/vhost_user.c
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@ -154,7 +154,22 @@ vhost_user_set_features(struct virtio_net *dev, uint64_t features)
return -1;
}
if ((dev->flags & VIRTIO_DEV_RUNNING) && dev->features != features) {
if (dev->flags & VIRTIO_DEV_RUNNING) {
if (dev->features == features)
return 0;
/*
* Error out if master tries to change features while device is
* in running state. The exception being VHOST_F_LOG_ALL, which
* is enabled when the live-migration starts.
*/
if ((dev->features ^ features) & ~(1ULL << VHOST_F_LOG_ALL)) {
RTE_LOG(ERR, VHOST_CONFIG,
"(%d) features changed while device is running.\n",
dev->vid);
return -1;
}
if (dev->notify_ops->features_changed)
dev->notify_ops->features_changed(dev->vid, features);
}