Commit 1d9d8639 authored by Stephane Eranian's avatar Stephane Eranian Committed by Linus Torvalds
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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
......@@ -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());
}
......@@ -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 */
......
......@@ -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))
......
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