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s390/cpum_cf: prepare for in-kernel counter measurements

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Prepare the counter facility support to be used by other in-kernel
users.  The first step introduces the __kernel_cpumcf_begin() and
__kernel_cpumcf_end() functions to reserve the counter facility
for doing measurements and to release after the measurements are
done.

Signed-off-by: Hendrik Brueckner <brueckner@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Hendrik Brueckner 2018-08-06 17:43:07 +02:00 committed by Martin Schwidefsky
parent 30e145f811
commit 3d33345aa3
2 changed files with 29 additions and 6 deletions
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3
arch/s390/include/asm/cpu_mcf.h
View file

@ -49,4 +49,7 @@ static inline void ctr_set_stop(u64 *state, int ctr_set)
*state &= ~(cpumf_ctr_ctl[ctr_set] << CPUMF_LCCTL_ACTCTL_SHIFT);
}
int __kernel_cpumcf_begin(void);
void __kernel_cpumcf_end(void);
#endif /* _ASM_S390_CPU_MCF_H */

32
arch/s390/kernel/perf_cpum_cf.c
View file

@ -236,25 +236,45 @@ static void setup_pmc_cpu(void *flags)
lcctl(0);
}
/* Initialize the CPU-measurement facility */
static int reserve_pmc_hardware(void)
/* Reserve/release functions for sharing perf hardware */
static DEFINE_SPINLOCK(cpumcf_owner_lock);
static void *cpumcf_owner;
/* Initialize the CPU-measurement counter facility */
int __kernel_cpumcf_begin(void)
{
int flags = PMC_INIT;
int err = 0;
spin_lock(&cpumcf_owner_lock);
if (cpumcf_owner)
err = -EBUSY;
else
cpumcf_owner = __builtin_return_address(0);
spin_unlock(&cpumcf_owner_lock);
if (err)
return err;
on_each_cpu(setup_pmc_cpu, &flags, 1);
irq_subclass_register(IRQ_SUBCLASS_MEASUREMENT_ALERT);
return 0;
}
EXPORT_SYMBOL(__kernel_cpumcf_begin);
/* Release the CPU-measurement facility */
static void release_pmc_hardware(void)
/* Release the CPU-measurement counter facility */
void __kernel_cpumcf_end(void)
{
int flags = PMC_RELEASE;
on_each_cpu(setup_pmc_cpu, &flags, 1);
irq_subclass_unregister(IRQ_SUBCLASS_MEASUREMENT_ALERT);
spin_lock(&cpumcf_owner_lock);
cpumcf_owner = NULL;
spin_unlock(&cpumcf_owner_lock);
}
EXPORT_SYMBOL(__kernel_cpumcf_end);
/* Release the PMU if event is the last perf event */
static void hw_perf_event_destroy(struct perf_event *event)
@ -262,7 +282,7 @@ static void hw_perf_event_destroy(struct perf_event *event)
if (!atomic_add_unless(&num_events, -1, 1)) {
mutex_lock(&pmc_reserve_mutex);
if (atomic_dec_return(&num_events) == 0)
release_pmc_hardware();
__kernel_cpumcf_end();
mutex_unlock(&pmc_reserve_mutex);
}
}
@ -363,7 +383,7 @@ static int __hw_perf_event_init(struct perf_event *event)
/* Initialize for using the CPU-measurement counter facility */
if (!atomic_inc_not_zero(&num_events)) {
mutex_lock(&pmc_reserve_mutex);
if (atomic_read(&num_events) == 0 && reserve_pmc_hardware())
if (atomic_read(&num_events) == 0 && __kernel_cpumcf_begin())
err = -EBUSY;
else
atomic_inc(&num_events);