From c54b2bf1b5e99760d53ea0376e96a046f93df6ae Mon Sep 17 00:00:00 2001 From: Anton Blanchard Date: Thu, 9 Apr 2015 12:52:56 +1000 Subject: [PATCH] powerpc: Add ppc64 hard lockup detector support The hard lockup detector uses a PMU event as a periodic NMI to detect if we are stuck (where stuck means no timer interrupts have occurred). Ben's rework of the ppc64 soft disable code has made ppc64 PMU exceptions a partial NMI. They can get disabled if an external interrupt comes in, but otherwise PMU interrupts will fire in interrupt disabled regions. We disable the hard lockup detector by default for a few reasons: - It breaks userspace event based branches on POWER8. - It is likely to produce false positives on KVM guests. - Since PMCs can only count to 2^31, counting cycles means we might take multiple PMU exceptions per second per hardware thread even if our hard lockup timeout is 10 seconds. It can be enabled via a boot option, or via procfs. Signed-off-by: Anton Blanchard Signed-off-by: Michael Ellerman --- arch/powerpc/Kconfig | 1 + arch/powerpc/include/asm/nmi.h | 4 ++++ arch/powerpc/kernel/setup_64.c | 20 ++++++++++++++++++++ 3 files changed, 25 insertions(+) create mode 100644 arch/powerpc/include/asm/nmi.h diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index c102668b4225..716c9e6a3160 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -152,6 +152,7 @@ config PPC select DCACHE_WORD_ACCESS if PPC64 && CPU_LITTLE_ENDIAN select NO_BOOTMEM select HAVE_GENERIC_RCU_GUP + select HAVE_PERF_EVENTS_NMI if PPC64 config GENERIC_CSUM def_bool CPU_LITTLE_ENDIAN diff --git a/arch/powerpc/include/asm/nmi.h b/arch/powerpc/include/asm/nmi.h new file mode 100644 index 000000000000..ff1ccb375e60 --- /dev/null +++ b/arch/powerpc/include/asm/nmi.h @@ -0,0 +1,4 @@ +#ifndef _ASM_NMI_H +#define _ASM_NMI_H + +#endif /* _ASM_NMI_H */ diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c index 49f553bbb360..7551e5692597 100644 --- a/arch/powerpc/kernel/setup_64.c +++ b/arch/powerpc/kernel/setup_64.c @@ -37,6 +37,7 @@ #include #include #include +#include #include #include @@ -779,3 +780,22 @@ unsigned long memory_block_size_bytes(void) struct ppc_pci_io ppc_pci_io; EXPORT_SYMBOL(ppc_pci_io); #endif + +#ifdef CONFIG_HARDLOCKUP_DETECTOR +u64 hw_nmi_get_sample_period(int watchdog_thresh) +{ + return ppc_proc_freq * watchdog_thresh; +} + +/* + * The hardlockup detector breaks PMU event based branches and is likely + * to get false positives in KVM guests, so disable it by default. + */ +static int __init disable_hardlockup_detector(void) +{ + watchdog_enable_hardlockup_detector(false); + + return 0; +} +early_initcall(disable_hardlockup_detector); +#endif -- 2.39.5