[PATCH v4 0/1] Memory hotplug fix

[Danylo Vodopianov]

Hi everyone.
We detected an issue with the memory hotplug feature and virtio devices while working with vitrio
in DPDK.In general, the issue is around the user request VHOST_USER_SET_MEM_TABLE and
locking queues for this request
(https://git.dpdk.org/dpdk-stable/tree/lib/vhost/vhost_user.c#n1512)
When the vhost_user receives the request VHOST_USER_SET_MEM_TABLE, it locks queues only
when the flag lock_all_qps is true(it is always true), AND the flag
VIRTIO_DEV_VDPA_CONFIGURED is not set.
https://git.dpdk.org/dpdk-stable/tree/lib/vhost/vhost_user.c#n3181
In the case of a memory hot plug, the flag VIRTIO_DEV_VDPA_CONFIGURED is always set,
and due to this, the queues are never locked while they are expected to be locked.
https://git.dpdk.org/dpdk-stable/tree/lib/vhost/vhost_user.c#n1512.
The quick solution is to add the check for request type and do lock queues always
if we have request VHOST_USER_SET_MEM_TABLE. Something like this, in general
https://git.dpdk.org/dpdk-stable/tree/lib/vhost/vhost_user.c#n3179

 if (!(dev->flags & VIRTIO_DEV_VDPA_CONFIGURED) ||
 request == VHOST_USER_SET_MEM_TABLE) {
 ...

Danylo Vodopianov (1):
  vhost: handle virtqueue locking for memory hotplug

 lib/vhost/vhost_user.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

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2.47.1