Re: [PATCH] cxl/events: Return IRQ_NONE when no event is pending

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] The `cxl_event_thread` can enter an infinite loop on device surprise removal or mailbox hardware failure, hanging the CPU and permanently masking a shared IRQ line.
--

commit f6cda8d59c7a077a8328222a63290241e9b118c0
Author: Shaikh Kamaluddin <shaikhkamal2012@gmail.com>
cxl/events: Return IRQ_NONE when no event is pending

This commit tracks whether at least one supported event status bit was observed
during interrupt handling. It returns IRQ_NONE when there was no event to
service, allowing the shared interrupt handler to behave correctly.

> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> index c7c91e8dc51dc..8b560cae91f2e 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/pci.c
> @@ -515,6 +515,7 @@ static irqreturn_t cxl_event_thread(int irq, void *id)

[ ... ]

>  		status &= CXLDEV_EVENT_STATUS_ALL;
>  		if (!status)
>  			break;
> +
> +		handled = true;
>  		cxl_mem_get_event_records(mds, status);
>  		cond_resched();
>  	} while (status);

[Severity: High]
This is a pre-existing issue, but can cxl_event_thread() get stuck in an
infinite loop here?

If a CXL device undergoes a surprise removal or a mailbox failure,
cxl_mem_get_records_log() can abort early without clearing the hardware
event status:

drivers/cxl/core/mbox.c:cxl_mem_get_records_log() {
    ...
		if (rc) {
			dev_err_ratelimited(dev,
				"Event log '%d': Failed to query event records : %d",
				type, rc);
			break;
		}
    ...
}

Because the local status variable evaluated in the while condition remains
non-zero, the loop will restart. If the memory-mapped read at the top of the
loop then returns 0xFFFFFFFF or the stuck status, the loop will spin endlessly,
permanently masking the shared interrupt line.

Should we add a mechanism to break out of this loop or track whether the
hardware status is actively being cleared?

>  
> -	return IRQ_HANDLED;
> +	return handled ? IRQ_HANDLED : IRQ_NONE;
>  }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260906155705.13252-1-shaikhkamal2012@gmail.com?part=1