Commit 1d9d8639 authored by Stephane Eranian's avatar Stephane Eranian Committed by Linus Torvalds
Browse files

perf,x86: fix kernel crash with PEBS/BTS after suspend/resume 



This patch fixes a kernel crash when using precise sampling (PEBS)
after a suspend/resume. Turns out the CPU notifier code is not invoked
on CPU0 (BP). Therefore, the DS_AREA (used by PEBS) is not restored properly
by the kernel and keeps it power-on/resume value of 0 causing any PEBS
measurement to crash when running on CPU0.

The workaround is to add a hook in the actual resume code to restore
the DS Area MSR value. It is invoked for all CPUS. So for all but CPU0,
the DS_AREA will be restored twice but this is harmless.

Reported-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarStephane Eranian <eranian@google.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent a2362d24

arch/x86/kernel/cpu/perf_event_intel_ds.c

+8 −0
Original line number Diff line number Diff line
@@ -729,3 +729,11 @@ void intel_ds_init(void) 
		}

	}

}



void perf_restore_debug_store(void)

{

	if (!x86_pmu.bts && !x86_pmu.pebs)

		return;



	init_debug_store_on_cpu(smp_processor_id());

}

arch/x86/power/cpu.c

+2 −0
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ 
#include <linux/suspend.h>

#include <linux/export.h>

#include <linux/smp.h>

#include <linux/perf_event.h>



#include <asm/pgtable.h>

#include <asm/proto.h>
@@ -228,6 +229,7 @@ static void __restore_processor_state(struct saved_context *ctxt) 
	do_fpu_end();

	x86_platform.restore_sched_clock_state();

	mtrr_bp_restore();

	perf_restore_debug_store();

}



/* Needed by apm.c */

include/linux/perf_event.h

+2 −0
Original line number Diff line number Diff line
@@ -758,6 +758,7 @@ extern void perf_event_enable(struct perf_event *event); 
extern void perf_event_disable(struct perf_event *event);

extern int __perf_event_disable(void *info);

extern void perf_event_task_tick(void);

extern void perf_restore_debug_store(void);

#else

static inline void

perf_event_task_sched_in(struct task_struct *prev,
@@ -797,6 +798,7 @@ static inline void perf_event_enable(struct perf_event *event) { } 
static inline void perf_event_disable(struct perf_event *event)		{ }

static inline int __perf_event_disable(void *info)			{ return -1; }

static inline void perf_event_task_tick(void)				{ }

static inline void perf_restore_debug_store(void)			{ }

#endif



#define perf_output_put(handle, x) perf_output_copy((handle), &(x), sizeof(x))

CRA Git | Maintained and supported by SUSTech CRA and CCSE