xen/events: Update virq_to_irq on migration

VIRQs come in 3 flavors, per-VPU, per-domain, and global, and the VIRQs
are tracked in per-cpu virq_to_irq arrays.

Per-domain and global VIRQs must be bound on CPU 0, and
bind_virq_to_irq() sets the per_cpu virq_to_irq at registration time
Later, the interrupt can migrate, and info->cpu is updated.  When
calling __unbind_from_irq(), the per-cpu virq_to_irq is cleared for a
different cpu.  If bind_virq_to_irq() is called again with CPU 0, the
stale irq is returned.  There won't be any irq_info for the irq, so
things break.

Make xen_rebind_evtchn_to_cpu() update the per_cpu virq_to_irq mappings
to keep them update to date with the current cpu.  This ensures the
correct virq_to_irq is cleared in __unbind_from_irq().

Fixes: e46cdb66 ("xen: event channels")
Cc: stable@vger.kernel.org
Signed-off-by: Jason Andryuk <jason.andryuk@amd.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Message-ID: <20250828003604.8949-4-jason.andryuk@amd.com>