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[V2,2/2] powerpc/perf: Fix the power10 event alternatives array to have correct sort order

Message ID 20220418145520.85753-2-atrajeev@linux.vnet.ibm.com (mailing list archive)
State Changes Requested
Headers show
Series [V2,1/2] powerpc/perf: Fix the power9 event alternatives array to have correct sort order | expand

Commit Message

Athira Rajeev April 18, 2022, 2:55 p.m. UTC 
When scheduling a group of events, there are constraint checks
done to make sure all events can go in a group. Example, one of
the criteria is that events in a group cannot use same PMC.
But platform specific PMU supports alternative event for some
of the event codes. During perf_event_open, if any event
group doesn't match constraint check criteria, further lookup
is done to find alternative event.

By current design, the array of alternatives events in PMU 
code is expected to be sorted by column 0. This is because in
find_alternative() function, the return criteria is based on
event code comparison. ie "event < ev_alt[i][0])". This
optimisation is there since find_alternative() can get called
multiple times. In power10 PMU code, the alternative event array
is not sorted list and hence there is breakage in finding 
alternative event.

To work with existing logic, fix the alternative event array
to be sorted by column 0 for power10-pmu.c

Fixes: a64e697cef23 ("powerpc/perf: power10 Performance Monitoring support")
Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Reviewed-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
---
Changelog:
 Added Fixes tag and reworded commit message
 Added Reviewed-by from Maddy

 arch/powerpc/perf/power10-pmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/arch/powerpc/perf/power10-pmu.c b/arch/powerpc/perf/power10-pmu.c
index d3398100a60f..c6d51e7093cf 100644
--- a/arch/powerpc/perf/power10-pmu.c
+++ b/arch/powerpc/perf/power10-pmu.c
@@ -91,8 +91,8 @@  extern u64 PERF_REG_EXTENDED_MASK;
 
 /* Table of alternatives, sorted by column 0 */
 static const unsigned int power10_event_alternatives[][MAX_ALT] = {
-	{ PM_CYC_ALT,			PM_CYC },
 	{ PM_INST_CMPL_ALT,		PM_INST_CMPL },
+	{ PM_CYC_ALT,			PM_CYC },
 };
 
 static int power10_get_alternatives(u64 event, unsigned int flags, u64 alt[])