Re: [PATCH v5] Drivers: hv: Avoid infinite retry loop in init_vp_index()

[Wei Liu]

On Mon, Aug 31, 2026 at 01:25:23AM +0000, Michael Kelley wrote:
> From: Waiman Long <longman@xxxxxxxxxx> Sent: Sunday, August 30, 2026 4:41 PM
> > 
> > There is a retry loop in init_vp_index() where the CPUs from a certain
> > node are stripped out if they have already been in the allocated cpumask
> > or not in HK_TYPE_MANAGED_IRQ housekeeping cpumask. If there is no
> > CPU left, the allocated cpumask is ignored and the process is retried
> > again. However, if the HK_TYPE_MANAGED_IRQ housekeeping cpumask turns
> > out not to contain any CPU in that particular node, that will become an
> > infinite retry loop.  This particular problem was reported by sashiko
> > [1]. This should rarely happen, but we still need to guard against this.
> > 
> > Fix this infinite loop problem by also skipping NUMA node that has no
> > housekeeping CPU in the inner while loop of init_vp_index(). Also update
> > the early abort check to check for the absence of online housekeeping
> > CPUs instead of just the emptiness of the cpumask. As the outer for
> > loop will only be reached if the housekeeping cpumask has at least one
> > online CPU, a NUMA node with housekeeping CPUs will eventually be found.
> > 
> > Link: https://sashiko.dev/#/message/20260422030903.E1BFCC2BCB0%40smtp.kernel.org [1]
> > Fixes: 6640b5df1a38 ("Drivers: hv: vmbus: Don't assign VMbus channel interrupts to isolated CPUs")
> > Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
> > ---
[...]
> 
> Looks good.
> 
> Reviewed-by: Michael Kelley <mhkelley@xxxxxxxxxxx>

Applied. Thank you both.

Wei

>