Re: [PATCH V5 20/38] migration: close kvm after cpr

[Peter Xu <peterx@redhat.com>]

On Wed, Jul 02, 2025 at 03:41:08PM -0400, Steven Sistare wrote:
> The irq producer is not closed, but it is detached from the kvm consumer.
> It's eventfd is preserved in new QEMU, and interrupts that arrive during
> transition are pended there.

Ah I see, looks reasonable.

So can I understand the core issue here is about the irq consumer /
provider updates are atomic, meanwhile there's always the fallback paths
ready, so before / after the update the irq won't get lost?

E.g. in Post-Interrupt context of Intel's, the irte will be updated
atomically for these VFIO irqs, so that either it'll keep using the fast
path (provided by the irqbypass mechanism), or slow path (eventfd_signal),
so it's free of any kind of race that irq could trigger?

I saw that there's already a new version and Cedric queued it.  If possible
add some explanation into commit message, either when repost, or when
merge, would be nice, on explaning irq won't get lost.

Thanks,

-- 
Peter Xu