Re: [PATCH v6 14/19] migration: add MIG_EVENT_PRE_INCOMING

[Peter Xu <peterx@redhat.com>]

On Tue, Sep 23, 2025 at 01:01:05PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> We are going to implement backend-transfer migration feature for
> virtio-net/tap. When it's enabled (by setting migration parameter), TAP
> device is passed through migration channel (which should be a unix
> socket to pass fds) to a new QEMU.
> 
> So we need to know during TAP initialization, should we open TAP
> device, or wait for incoming fds. But we can't check for migration
> parameter at TAP creation time, as use may set migration parameter
> later (especially when TAP is added by command line parameter).
> 
> To solve this, we have prepared TAP initialization code so that
> opening the device may be postponed to later point. And this later
> point is obviously the early beginning of qmp_migrate_incoming():
> here we already know all migration parameters and capabilities,
> but we are not in downtime, so we can continue initialization
> of TAP device.
> 
> This commit introduces MIG_EVENT_PRE_INCOMING, to be used by TAP
> code in following commit.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>

Acked-by: Peter Xu <peterx@redhat.com>

-- 
Peter Xu