From 92ca7da4bdc24d63bb0bcd241c11441ddb63b80a Mon Sep 17 00:00:00 2001 From: Alexander Shishkin Date: Tue, 10 Dec 2019 12:51:01 +0200 Subject: perf/x86/intel: Fix PT PMI handling Commit: ccbebba4c6bf ("perf/x86/intel/pt: Bypass PT vs. LBR exclusivity if the core supports it") skips the PT/LBR exclusivity check on CPUs where PT and LBRs coexist, but also inadvertently skips the active_events bump for PT in that case, which is a bug. If there aren't any hardware events at the same time as PT, the PMI handler will ignore PT PMIs, as active_events reads zero in that case, resulting in the "Uhhuh" spurious NMI warning and PT data loss. Fix this by always increasing active_events for PT events. Fixes: ccbebba4c6bf ("perf/x86/intel/pt: Bypass PT vs. LBR exclusivity if the core supports it") Reported-by: Vitaly Slobodskoy Signed-off-by: Alexander Shishkin Signed-off-by: Peter Zijlstra (Intel) Acked-by: Alexey Budankov Cc: Jiri Olsa Cc: Ingo Molnar Cc: Arnaldo Carvalho de Melo Link: https://lkml.kernel.org/r/20191210105101.77210-1-alexander.shishkin@linux.intel.com --- arch/x86/events/core.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'arch/x86/events') diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c index 84fe1becbe26..f118af9f0718 100644 --- a/arch/x86/events/core.c +++ b/arch/x86/events/core.c @@ -376,7 +376,7 @@ int x86_add_exclusive(unsigned int what) * LBR and BTS are still mutually exclusive. */ if (x86_pmu.lbr_pt_coexist && what == x86_lbr_exclusive_pt) - return 0; + goto out; if (!atomic_inc_not_zero(&x86_pmu.lbr_exclusive[what])) { mutex_lock(&pmc_reserve_mutex); @@ -388,6 +388,7 @@ int x86_add_exclusive(unsigned int what) mutex_unlock(&pmc_reserve_mutex); } +out: atomic_inc(&active_events); return 0; @@ -398,11 +399,15 @@ fail_unlock: void x86_del_exclusive(unsigned int what) { + atomic_dec(&active_events); + + /* + * See the comment in x86_add_exclusive(). + */ if (x86_pmu.lbr_pt_coexist && what == x86_lbr_exclusive_pt) return; atomic_dec(&x86_pmu.lbr_exclusive[what]); - atomic_dec(&active_events); } int x86_setup_perfctr(struct perf_event *event) -- cgit v1.2.3