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 <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index c102668..716c9e6 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -152,6 +152,7 @@
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