vhost/vsock: add VHOST_RESET_OWNER ioctl

This ioctl is needed for QEMU's CPR (checkpoint-restore) migration of
the guest with vhost-vsock device.  For this to work, we need to reset
the device ownership on the source side by calling RESET_OWNER, and then
claim it on the dest side by calling SET_OWNER.  We expect not to lose any
AF_VSOCK connection while this happens.

To that end, unlike the release path, RESET_OWNER keeps the guest CID
hashed: established connections survive, and host sends issued while
the device is between owners simply stay on send_pkt_queue until the
next device start drains them.

Since the device stays reachable through the CID hash, the lockless
send/cancel paths can race with the worker teardown in
vhost_workers_free().  The previous commit ("vhost: synchronize with
RCU readers when freeing workers") makes that safe.

Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Message-ID: <20260720102241.371610-6-andrey.drobyshev@virtuozzo.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

0 files changed, 0 insertions, 0 deletions