Commit cf6acb8bdb ("s390/cpumf: Add support for complete counter set extraction")
allows access to the CPU Measurement Counter Facility via character
device /dev/hwctr. The access was exclusive via this device or
via perf_event_open() system call. Only one path at a time was
permitted. The CPU Measurement Counter Facility device driver blocked
access to other processes.
This patch removes this restriction and allows concurrent access to
the CPU Measurement Counter Facility from multiple processes at the same
time via perf_event_open() SVC and via /dev/hwctr device. The access
via /dev/hwctr device is still exclusive, only one process is allowed to
access this device.
This patch
- moves the /dev/hwctr device access from file perf_cpum_cf_diag.c.
to file perf_cpum_cf.c.
- use only one trace buffer .../s390dbf/cpum_cf.
- remove cfset_csd structure and includes its members it into the
structure cpu_cf_events. This results in one data structure and
simplifies the access.
- rework function familiy ctr_set_enable, ctr_set_disable, ctr_set_start
and ctr_set_stop which operate on a counter set number.
Now they operate on a counter set bit mask.
- move CF_DIAG event functionality to file perf_cpum_cf.c. It now
contains the complete functionality of the CPU Measurement Counter
Facility:
- Performance measurement support for counters using perf stat.
- Support for complete counter set extraction with device /dev/hwctr.
- Support for counter set extraction event CF_DIAG attached to
samples using perf record.
- removes file perf_cpum_cf_diag.c
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>
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>
The function to calculate the size of counter sets is renamed from
cf_diag_ctrset_size() to cpum_cf_ctrset_size() and moved to the file
containing common functions for the CPU Measurement Counter Facility.
No functional change.
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Acked-by : Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Move common functions of the couter facility support into a separate
file.
Signed-off-by: Hendrik Brueckner <brueckner@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Thomas Richter
Hendrik Brueckner