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powerpc/64s: Implement PMU override command line option

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It can be useful in simulators (with very constrained environments)
to allow some PMCs to run from boot so they can be sampled directly
by a test harness, rather than having to run perf.

A previous change freezes counters at boot by default, so provide
a boot time option to un-freeze (plus a bit more flexibility).

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211123095231.1036501-13-npiggin@gmail.com
This commit is contained in:
Nicholas Piggin 2021-11-23 19:51:50 +10:00 committed by Michael Ellerman
parent 245ebf8e73
commit 0a4b4327ce
2 changed files with 43 additions and 0 deletions
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8
Documentation/admin-guide/kernel-parameters.txt
View File

@ -4144,6 +4144,14 @@
Override pmtimer IOPort with a hex value.
e.g. pmtmr=0x508
pmu_override= [PPC] Override the PMU.
This option takes over the PMU facility, so it is no
longer usable by perf. Setting this option starts the
PMU counters by setting MMCR0 to 0 (the FC bit is
cleared). If a number is given, then MMCR1 is set to
that number, otherwise (e.g., 'pmu_override=on'), MMCR1
remains 0.
pm_debug_messages [SUSPEND,KNL]
Enable suspend/resume debug messages during boot up.

35
arch/powerpc/perf/core-book3s.c
View File

@ -2419,8 +2419,24 @@ int register_power_pmu(struct power_pmu *pmu)
}
#ifdef CONFIG_PPC64
static bool pmu_override = false;
static unsigned long pmu_override_val;
static void do_pmu_override(void *data)
{
ppc_set_pmu_inuse(1);
if (pmu_override_val)
mtspr(SPRN_MMCR1, pmu_override_val);
mtspr(SPRN_MMCR0, mfspr(SPRN_MMCR0) & ~MMCR0_FC);
}
static int __init init_ppc64_pmu(void)
{
if (cpu_has_feature(CPU_FTR_HVMODE) && pmu_override) {
pr_warn("disabling perf due to pmu_override= command line option.\n");
on_each_cpu(do_pmu_override, NULL, 1);
return 0;
}
/* run through all the pmu drivers one at a time */
if (!init_power5_pmu())
return 0;
@ -2442,4 +2458,23 @@ static int __init init_ppc64_pmu(void)
return init_generic_compat_pmu();
}
early_initcall(init_ppc64_pmu);
static int __init pmu_setup(char *str)
{
unsigned long val;
if (!early_cpu_has_feature(CPU_FTR_HVMODE))
return 0;
pmu_override = true;
if (kstrtoul(str, 0, &val))
val = 0;
pmu_override_val = val;
return 1;
}
__setup("pmu_override=", pmu_setup);
#endif