Commit d552a58d authored by Thomas Richter's avatar Thomas Richter Committed by Vasily Gorbik
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s390/cpumf: remove counter transaction call backs 



The command 'perf stat -e cycles ...' triggers the following function
sequence in the CPU Measurement Facility counter device driver:

perf_pmu_event_init()
  __hw_perf_event_init()
    validate_ctr_auth()
    validate_ctr_version()

During event creation, the counter number is checked in functions
validate_ctr_auth() and validate_ctr_version() to verify it is a valid
counter and supported by the hardware. If this is not the case, both
functions return an error and the event is not created. System call
perf_event_open() returns an error in this case.

Later on the event is installed in the kernel event subsystem and the
driver functions cpumf_pmu_add() and cpumf_pmu_commit_txn() are called
to install the counter event by the hardware.

Since both events have been verified at event creation, there is no need
to re-evaluate the authorization state. This can not change since on
 * LPARs the authorization change requires a restart of the LPAR (and
   thus a reboot of the kernel)
 * DPMs can not take resources away, just add them.

Also the sequence of CPU Measurement facility counter device driver
calls is
  cpumf_pmu_start_txn
  cpumf_pmu_add
  cpumf_pmu_start
  cpumf_pmu_commit_txn
for every single event. Which means the condition in cpumf_pmu_add()
is never met and validate_ctr_auth() is never called.

This leaves the counter device driver transaction functions with
just one task:
start_txn: Verify a transaction is not in flight and call
	perf_pmu_disable()
cancel_txn, commit_txn: Verify a transaction is in flight and call
	perf_pmu_enable()

The same functionality is provided by the default transaction handling
functions in kernel/events/core.c. Use those by removing the
counter device driver private call back functions.

Suggested-by: default avatarSumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: default avatarThomas Richter <tmricht@linux.ibm.com>
Reviewed-by: default avatarSumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent 614124be

arch/s390/include/asm/cpu_mcf.h

+1 −2
Original line number Diff line number Diff line
@@ -92,9 +92,8 @@ struct cpu_cf_events { 
	struct cpumf_ctr_info	info;

	atomic_t		ctr_set[CPUMF_CTR_SET_MAX];

	atomic64_t		alert;

	u64			state, tx_state;

	u64			state;

	unsigned int		flags;

	unsigned int		txn_flags;

};

DECLARE_PER_CPU(struct cpu_cf_events, cpu_cf_events);

arch/s390/kernel/perf_cpum_cf.c

+0 −84
Original line number Diff line number Diff line
@@ -413,15 +413,6 @@ static int cpumf_pmu_add(struct perf_event *event, int flags) 
{

	struct cpu_cf_events *cpuhw = this_cpu_ptr(&cpu_cf_events);



	/* Check authorization for the counter set to which this

	 * counter belongs.

	 * For group events transaction, the authorization check is

	 * done in cpumf_pmu_commit_txn().

	 */

	if (!(cpuhw->txn_flags & PERF_PMU_TXN_ADD))

		if (validate_ctr_auth(&event->hw))

			return -ENOENT;



	ctr_set_enable(&cpuhw->state, event->hw.config_base);

	event->hw.state = PERF_HES_UPTODATE | PERF_HES_STOPPED;
@@ -449,78 +440,6 @@ static void cpumf_pmu_del(struct perf_event *event, int flags) 
		ctr_set_disable(&cpuhw->state, event->hw.config_base);

}



/*

 * Start group events scheduling transaction.

 * Set flags to perform a single test at commit time.

 *

 * We only support PERF_PMU_TXN_ADD transactions. Save the

 * transaction flags but otherwise ignore non-PERF_PMU_TXN_ADD

 * transactions.

 */

static void cpumf_pmu_start_txn(struct pmu *pmu, unsigned int txn_flags)

{

	struct cpu_cf_events *cpuhw = this_cpu_ptr(&cpu_cf_events);



	WARN_ON_ONCE(cpuhw->txn_flags);		/* txn already in flight */



	cpuhw->txn_flags = txn_flags;

	if (txn_flags & ~PERF_PMU_TXN_ADD)

		return;



	perf_pmu_disable(pmu);

	cpuhw->tx_state = cpuhw->state;

}



/*

 * Stop and cancel a group events scheduling tranctions.

 * Assumes cpumf_pmu_del() is called for each successful added

 * cpumf_pmu_add() during the transaction.

 */

static void cpumf_pmu_cancel_txn(struct pmu *pmu)

{

	unsigned int txn_flags;

	struct cpu_cf_events *cpuhw = this_cpu_ptr(&cpu_cf_events);



	WARN_ON_ONCE(!cpuhw->txn_flags);	/* no txn in flight */



	txn_flags = cpuhw->txn_flags;

	cpuhw->txn_flags = 0;

	if (txn_flags & ~PERF_PMU_TXN_ADD)

		return;



	WARN_ON(cpuhw->tx_state != cpuhw->state);



	perf_pmu_enable(pmu);

}



/*

 * Commit the group events scheduling transaction.  On success, the

 * transaction is closed.   On error, the transaction is kept open

 * until cpumf_pmu_cancel_txn() is called.

 */

static int cpumf_pmu_commit_txn(struct pmu *pmu)

{

	struct cpu_cf_events *cpuhw = this_cpu_ptr(&cpu_cf_events);

	u64 state;



	WARN_ON_ONCE(!cpuhw->txn_flags);	/* no txn in flight */



	if (cpuhw->txn_flags & ~PERF_PMU_TXN_ADD) {

		cpuhw->txn_flags = 0;

		return 0;

	}



	/* check if the updated state can be scheduled */

	state = cpuhw->state & ~((1 << CPUMF_LCCTL_ENABLE_SHIFT) - 1);

	state >>= CPUMF_LCCTL_ENABLE_SHIFT;

	if ((state & cpuhw->info.auth_ctl) != state)

		return -ENOENT;



	cpuhw->txn_flags = 0;

	perf_pmu_enable(pmu);

	return 0;

}



/* Performance monitoring unit for s390x */

static struct pmu cpumf_pmu = {

	.task_ctx_nr  = perf_sw_context,
@@ -533,9 +452,6 @@ static struct pmu cpumf_pmu = { 
	.start	      = cpumf_pmu_start,

	.stop	      = cpumf_pmu_stop,

	.read	      = cpumf_pmu_read,

	.start_txn    = cpumf_pmu_start_txn,

	.commit_txn   = cpumf_pmu_commit_txn,

	.cancel_txn   = cpumf_pmu_cancel_txn,

};



static int __init cpumf_pmu_init(void)

arch/s390/kernel/perf_cpum_cf_common.c

+0 −1
Original line number Diff line number Diff line
@@ -30,7 +30,6 @@ DEFINE_PER_CPU(struct cpu_cf_events, cpu_cf_events) = { 
	.alert = ATOMIC64_INIT(0),

	.state = 0,

	.flags = 0,

	.txn_flags = 0,

};

/* Indicator whether the CPU-Measurement Counter Facility Support is ready */

static bool cpum_cf_initalized;