Patch "perf/x86: Fix n_pair for cancelled txn" has been added to the 5.9-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    perf/x86: Fix n_pair for cancelled txn

to the 5.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     perf-x86-fix-n_pair-for-cancelled-txn.patch
and it can be found in the queue-5.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 02a6d2f07c61e9fc7b999b18fb518c090723709e
Author: Sasha Levin <sashal@xxxxxxxxxx>
Date:   Mon Oct 12 23:28:52 2020 -0400

    perf/x86: Fix n_pair for cancelled txn
    
    [ Upstream commit 871a93b0aad65a7f44ee25f2d17932ef6d559850 ]
    
    Kan reported that n_metric gets corrupted for cancelled transactions;
    a similar issue exists for n_pair for AMD's Large Increment thing.
    
    The problem was confirmed and confirmed fixed by Kim using:
    
      sudo perf stat -e "{cycles,cycles,cycles,cycles}:D" -a sleep 10 &
    
      # should succeed:
      sudo perf stat -e "{fp_ret_sse_avx_ops.all}:D" -a workload
    
      # should fail:
      sudo perf stat -e "{fp_ret_sse_avx_ops.all,fp_ret_sse_avx_ops.all,cycles}:D" -a workload
    
      # previously failed, now succeeds with this patch:
      sudo perf stat -e "{fp_ret_sse_avx_ops.all}:D" -a workload
    
    Fixes: 5738891229a2 ("perf/x86/amd: Add support for Large Increment per Cycle Events")
    Reported-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
    Tested-by: Kim Phillips <kim.phillips@xxxxxxx>
    Link: https://lkml.kernel.org/r/20201005082516.GG2628@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 1cbf57dc2ac89..11bbc6590f904 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -1087,8 +1087,10 @@ static int collect_events(struct cpu_hw_events *cpuc, struct perf_event *leader,
 
 		cpuc->event_list[n] = event;
 		n++;
-		if (is_counter_pair(&event->hw))
+		if (is_counter_pair(&event->hw)) {
 			cpuc->n_pair++;
+			cpuc->n_txn_pair++;
+		}
 	}
 	return n;
 }
@@ -1962,6 +1964,7 @@ static void x86_pmu_start_txn(struct pmu *pmu, unsigned int txn_flags)
 
 	perf_pmu_disable(pmu);
 	__this_cpu_write(cpu_hw_events.n_txn, 0);
+	__this_cpu_write(cpu_hw_events.n_txn_pair, 0);
 }
 
 /*
@@ -1987,6 +1990,7 @@ static void x86_pmu_cancel_txn(struct pmu *pmu)
 	 */
 	__this_cpu_sub(cpu_hw_events.n_added, __this_cpu_read(cpu_hw_events.n_txn));
 	__this_cpu_sub(cpu_hw_events.n_events, __this_cpu_read(cpu_hw_events.n_txn));
+	__this_cpu_sub(cpu_hw_events.n_pair, __this_cpu_read(cpu_hw_events.n_txn_pair));
 	perf_pmu_enable(pmu);
 }
 
diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index 7b68ab5f19e76..0e74235cdac9e 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -210,6 +210,7 @@ struct cpu_hw_events {
 					     they've never been enabled yet */
 	int			n_txn;    /* the # last events in the below arrays;
 					     added in the current transaction */
+	int			n_txn_pair;
 	int			assign[X86_PMC_IDX_MAX]; /* event to counter assignment */
 	u64			tags[X86_PMC_IDX_MAX];