perf/x86/intel/bts: Check if bts_ctx is allocated when calling BTS functions

bts_ctx might not be allocated, for example if the CPU has X86_FEATURE_PTI,
but intel_bts_disable/enable_local() and intel_bts_interrupt() are called
unconditionally from intel_pmu_handle_irq() and crash on bts_ctx.

So check if bts_ctx is allocated when calling BTS functions.

Fixes: 3acfcefa795c ("perf/x86/intel/bts: Allocate bts_ctx only if necessary")
Reported-by: Jiri Olsa <olsajiri@gmail.com>
Tested-by: Jiri Olsa <jolsa@kernel.org>
Suggested-by: Adrian Hunter <adrian.hunter@intel.com>
Suggested-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250306051102.2642-1-lirongqing@baidu.com

diff --git a/arch/x86/events/intel/bts.c b/arch/x86/events/intel/bts.c
index 953868da82fb452d00db055d9082b4db905d7c2b..39a987d5eb6e06c262488650febf036041773886 100644 (file)
--- a/arch/x86/events/intel/bts.c
+++ b/arch/x86/events/intel/bts.c
@@ -338,9 +338,14 @@ static void bts_event_stop(struct perf_event *event, int flags)
 
 void intel_bts_enable_local(void)
 {
-       struct bts_ctx *bts = this_cpu_ptr(bts_ctx);
-       int state = READ_ONCE(bts->state);
+       struct bts_ctx *bts;
+       int state;
 
+       if (!bts_ctx)
+               return;
+
+       bts = this_cpu_ptr(bts_ctx);
+       state = READ_ONCE(bts->state);
        /*
         * Here we transition from INACTIVE to ACTIVE;
         * if we instead are STOPPED from the interrupt handler,
@@ -358,7 +363,12 @@ void intel_bts_enable_local(void)
 
 void intel_bts_disable_local(void)
 {
-       struct bts_ctx *bts = this_cpu_ptr(bts_ctx);
+       struct bts_ctx *bts;
+
+       if (!bts_ctx)
+               return;
+
+       bts = this_cpu_ptr(bts_ctx);
 
        /*
         * Here we transition from ACTIVE to INACTIVE;
@@ -450,12 +460,17 @@ bts_buffer_reset(struct bts_buffer *buf, struct perf_output_handle *handle)
 int intel_bts_interrupt(void)
 {
        struct debug_store *ds = this_cpu_ptr(&cpu_hw_events)->ds;
-       struct bts_ctx *bts = this_cpu_ptr(bts_ctx);
-       struct perf_event *event = bts->handle.event;
+       struct bts_ctx *bts;
+       struct perf_event *event;
        struct bts_buffer *buf;
        s64 old_head;
        int err = -ENOSPC, handled = 0;
 
+       if (!bts_ctx)
+               return 0;
+
+       bts = this_cpu_ptr(bts_ctx);
+       event = bts->handle.event;
        /*
         * The only surefire way of knowing if this NMI is ours is by checking
         * the write ptr against the PMI threshold.