[PATCH v3 1/9] perf/cxl: Program the requested event group on configurable counters

cxl_pmu_get_event_idx() sets *counter_idx for a configurable counter but
never *event_idx. hwc->event_base stays 0, so cxl_pmu_event_start()
programs event group 0 no matter which group the user asked for.

Return the matched capability's event_idx.

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
Reviewed-by: Jonathan Cameron <[email protected]>
Signed-off-by: Dave Jiang <[email protected]>
---
v3:
- Check event_idx alongside counter_idx at the top of the scope. (Jonathan)
---
 drivers/perf/cxl_pmu.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/perf/cxl_pmu.c b/drivers/perf/cxl_pmu.c
index 68a54d97d2a8..ff01b658e1b4 100644
--- a/drivers/perf/cxl_pmu.c
+++ b/drivers/perf/cxl_pmu.c
@@ -513,7 +513,10 @@ static const struct attribute_group *cxl_pmu_attr_groups[] = {
 	NULL
 };
 
-/* If counter_idx == NULL, don't try to allocate a counter. */
+/*
+ * If counter_idx == NULL, don't try to allocate a counter. Callers that
+ * allocate pass both counter_idx and event_idx.
+ */
 static int cxl_pmu_get_event_idx(struct perf_event *event, int *counter_idx,
 				 int *event_idx)
 {
@@ -541,7 +544,7 @@ static int cxl_pmu_get_event_idx(struct perf_event *event, int *counter_idx,
 
 	pmu_ev = cxl_pmu_find_config_counter_ev_cap(info, vid, gid, mask);
 	if (!IS_ERR(pmu_ev)) {
-		if (!counter_idx)
+		if (!counter_idx || !event_idx)
 			return 0;
 
 		bitmap_andnot(configurable_and_free, info->conf_counter_bm,
@@ -552,6 +555,7 @@ static int cxl_pmu_get_event_idx(struct perf_event *event, int *counter_idx,
 			return -EINVAL;
 
 		*counter_idx = i;
+		*event_idx = pmu_ev->event_idx;
 		return 0;
 	}
 
-- 
2.55.0