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

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.

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 410c9162c824..7db858727ac6 100644
--- a/drivers/perf/cxl_pmu.c
+++ b/drivers/perf/cxl_pmu.c
@@ -864,7 +864,7 @@ 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);
-- 
2.55.0