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

On 7/30/26 5:18 AM, Robin Murphy 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?

So info->irq reverts back to Linux vIRQ after the irq is requested. It's kind of messy. Maybe we should split it into two fields to remove the confusion? I can create a patch for that before this patch change.

DJ

> 
> 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: [email protected]
>> Closes: https://sashiko.dev/#/patchset/[email protected]?part=1
>> Assisted-by: Claude:claude-opus-4-8
>> Signed-off-by: Dave Jiang <[email protected]>
>> ---
>>   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);
>