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s390/cpumf: remove counter transaction call backs

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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: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Reviewed-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Thomas Richter 2021-04-28 13:30:56 +02:00 committed by Vasily Gorbik
parent 614124bea7
commit d552a58d70
3 changed files with 1 additions and 87 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
arch/s390/include/asm/cpu_mcf.h
View File

@ -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);

84
arch/s390/kernel/perf_cpum_cf.c
View File

@ -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)

1
arch/s390/kernel/perf_cpum_cf_common.c
View File

@ -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;