From cf6acb8bdb1d829b85a4daa2944bf9e71c93f4b9 Mon Sep 17 00:00:00 2001 From: Thomas Richter Date: Mon, 22 Feb 2021 18:01:54 +0100 Subject: s390/cpumf: Add support for complete counter set extraction Add support to the CPU Measurement counter facility device driver to extract complete counter sets per CPU and per counter set from user space. This includes a new device named /dev/hwctr and support for the device driver functions open, close and ioctl. Other functions are not supported. The ioctl command supports 3 subcommands: S390_HWCTR_START: enables counter sets on a list of CPUs. S390_HWCTR_STOP: disables counter sets on a list of CPUs. S390_HWCTR_READ: reads counter sets on a list of CPUs. The ioctl(..., S390_HWCTR_READ, ...) is the only subcommand which returns data. It requires member data_bytes to be positive and indicates the maximum amount of data available to store counter set data. The other ioctl() subcommands do not use this member and it should be set to zero. The S390_HWCTR_READ subcommand returns the following data: The cpuset data is flattened using the following scheme, stored in member data: 0x0 0x8 0xc 0x10 0x10 0x18 0x20 0x28 0xU-1 +---------+-----+---------+-----+---------+-----+-----+------+------+ | no_cpus | cpu | no_sets | set | no_cnts | cv1 | cv2 | .... | cv_n | +---------+-----+---------+-----+---------+-----+-----+------+------+ 0xU 0xU+4 0xU+8 0xU+10 0xV-1 +-----+---------+-----+-----+------+------+ | set | no_cnts | cv1 | cv2 | .... | cv_n | +-----+---------+-----+-----+------+------+ 0xV 0xV+4 0xV+8 0xV+c +-----+---------+-----+---------+-----+-----+------+------+ | cpu | no_sets | set | no_cnts | cv1 | cv2 | .... | cv_n | +-----+---------+-----+---------+-----+-----+------+------+ U and V denote arbitrary hexadezimal addresses. The first integer represents the number of CPUs data was extracted from. This is followed by CPU number and number of counter sets extracted. Both are two integer values. This is followed by the set identifer and number of counters extracted. Both are two integer values. This is followed by the counter values, each element is eight bytes in size. The S390_HWCTR_READ ioctl subcommand is also limited to one call per minute. This ensures that an application does not read out the counter sets too often and reduces the overall CPU performance. The complete counter set extraction is an expensive operation. Reviewed-by: Sumanth Korikkar Signed-off-by: Thomas Richter Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik --- include/linux/cpuhotplug.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include') diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h index ee09a39627d6..9129ba231423 100644 --- a/include/linux/cpuhotplug.h +++ b/include/linux/cpuhotplug.h @@ -168,6 +168,7 @@ enum cpuhp_state { CPUHP_AP_PERF_X86_CQM_ONLINE, CPUHP_AP_PERF_X86_CSTATE_ONLINE, CPUHP_AP_PERF_S390_CF_ONLINE, + CPUHP_AP_PERF_S390_CFD_ONLINE, CPUHP_AP_PERF_S390_SF_ONLINE, CPUHP_AP_PERF_ARM_CCI_ONLINE, CPUHP_AP_PERF_ARM_CCN_ONLINE, -- cgit v1.2.3-58-ga151