Re: [PATCH v2 4/9] perf/cxl: Accept an overflow interrupt on MSI message number 0

[Jonathan Cameron <jic23@kernel.org>]

On Thu, 30 Jul 2026 13:18:42 +0100
Robin Murphy <robin.murphy@arm.com> wrote:

> On 29/07/2026 3:55 pm, Dave Jiang wrote:
> > cxl_pmu_probe() rejects the PMU with -EINVAL when info->irq <= 0, but
> > info->irq holds the MSI/MSI-X message number the device signals overflow
> > on (CXL_PMU_CAP_MSI_N_MSK, a 0-based 4-bit field), with -1 meaning "no
> > interrupt support". Message number 0 is valid and pci_irq_vector() takes
> > a 0-based index, so a compliant device signalling on the first vector is
> > wrongly refused and fails to probe.  
> 
> If info->irq is a PCI MSI vector index, not the Linux vIRQ number, then 
> surely that means the irq_set_affinity() calls are wrong as well?

yup.  I really messed this driver up :(

should rename this one and then have irq mean irq.


> 
> Thanks,
> Robin.
> 
> > Reject only the no-interrupt case (info->irq < 0), matching the sibling
> > CXL mailbox and event IRQ handling.
> > 
> > Fixes: 5d7107c72796 ("perf: CXL Performance Monitoring Unit driver")
> > Reported-by: sashiko-bot@kernel.org
> > Closes: https://sashiko.dev/#/patchset/20260715191454.459673-1-dave@stgolabs.net?part=1
> > Assisted-by: Claude:claude-opus-4-8
> > Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> > ---
> >   drivers/perf/cxl_pmu.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/perf/cxl_pmu.c b/drivers/perf/cxl_pmu.c
> > index 956da8202551..d1e810601e36 100644
> > --- a/drivers/perf/cxl_pmu.c
> > +++ b/drivers/perf/cxl_pmu.c
> > @@ -876,7 +876,7 @@ static int cxl_pmu_probe(struct device *dev)
> >   		.capabilities = PERF_PMU_CAP_NO_EXCLUDE,
> >   	};
> >   
> > -	if (info->irq <= 0)
> > +	if (info->irq < 0)
> >   		return -EINVAL;
> >   
> >   	rc = pci_irq_vector(pdev, info->irq);  
>