Re: [PATCH v6 5/5] vhost/vsock: add VHOST_RESET_OWNER ioctl

[Stefano Garzarella <sgarzare@redhat.com>]

On Fri, Jul 24, 2026 at 02:45:42PM +0300, Andrey Drobyshev wrote:
>From: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
>
>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>
>---
> drivers/vhost/vsock.c | 32 ++++++++++++++++++++++++++++++++
> 1 file changed, 32 insertions(+)

I thought I had already reviewed this, but anyway:

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>