linux-kernel - [PATCH] perf/x86/intel/cqm: Check cqm/mbm enabled state in event init

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Date:   Mon,  5 Sep 2016 17:30:07 +0200
From:   Jiri Olsa <jolsa@...nel.org>
To:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Yanqiu Zhang <yanqzhan@...hat.com>,
        Tony Luck <tony.luck@...el.com>,
        Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH] perf/x86/intel/cqm: Check cqm/mbm enabled state in event init

Yanqiu Zhang reported kernel panic when using mbm event
on system where CQM is detected but without mbm event
support, like with perf:

  # perf stat -e 'intel_cqm/event=3/' -a

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
  IP: [<ffffffff8100d64c>] update_sample+0xbc/0xe0
  ...
   <IRQ>
   [<ffffffff8100d688>] __intel_mbm_event_init+0x18/0x20
   [<ffffffff81113d6b>] flush_smp_call_function_queue+0x7b/0x160
   [<ffffffff81114853>] generic_smp_call_function_single_interrupt+0x13/0x60
   [<ffffffff81052017>] smp_call_function_interrupt+0x27/0x40
   [<ffffffff816fb06c>] call_function_interrupt+0x8c/0xa0
  ...

The reason is that we currently allow to init mbm event
even if mbm support is not detected.  Adding checks for
both cqm and mbm events and support into cqm's event_init.

Reported-by: Yanqiu Zhang <yanqzhan@...hat.com>
Signed-off-by: Jiri Olsa <jolsa@...hat.com>
---
 arch/x86/events/intel/cqm.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/x86/events/intel/cqm.c b/arch/x86/events/intel/cqm.c
index 783c49ddef29..8f82b02934fa 100644
--- a/arch/x86/events/intel/cqm.c
+++ b/arch/x86/events/intel/cqm.c
@@ -458,6 +458,11 @@ static void __intel_cqm_event_count(void *info);
 static void init_mbm_sample(u32 rmid, u32 evt_type);
 static void __intel_mbm_event_count(void *info);
 
+static bool is_cqm_event(int e)
+{
+	return (e == QOS_L3_OCCUP_EVENT_ID);
+}
+
 static bool is_mbm_event(int e)
 {
 	return (e >= QOS_MBM_TOTAL_EVENT_ID && e <= QOS_MBM_LOCAL_EVENT_ID);
@@ -1366,6 +1371,10 @@ static int intel_cqm_event_init(struct perf_event *event)
 	     (event->attr.config > QOS_MBM_LOCAL_EVENT_ID))
 		return -EINVAL;
 
+	if ((is_cqm_event(event->attr.config) && !cqm_enabled) ||
+	    (is_mbm_event(event->attr.config) && !mbm_enabled))
+		return -EINVAL;
+
 	/* unsupported modes and filters */
 	if (event->attr.exclude_user   ||
 	    event->attr.exclude_kernel ||
-- 
2.7.4