Mike Travis 0d12ef0c90 x86/UV: Update UV support for external NMI signals ... The current UV NMI handler has not been updated for the changes in the system NMI handler and the perf operations. The UV NMI handler reads an MMR in the UV Hub to check to see if the NMI event was caused by the external 'system NMI' that the operator can initiate on the System Mgmt Controller. The problem arises when the perf tools are running, causing millions of perf events per second on very large CPU count systems. Previously this was okay because the perf NMI handler ran at a higher priority on the NMI call chain and if the NMI was a perf event, it would stop calling other NMI handlers remaining on the NMI call chain. Now the system NMI handler calls all the handlers on the NMI call chain including the UV NMI handler. This causes the UV NMI handler to read the MMRs at the same millions per second rate. This can lead to significant performance loss and possible system failures. It also can cause thousands of 'Dazed and Confused' messages being sent to the system console. This effectively makes perf tools unusable on UV systems. To avoid this excessive overhead when perf tools are running, this code has been optimized to minimize reading of the MMRs as much as possible, by moving to the NMI_UNKNOWN notifier chain. This chain is called only when all the users on the standard NMI_LOCAL call chain have been called and none of them have claimed this NMI. There is an exception where the NMI_LOCAL notifier chain is used. When the perf tools are in use, it's possible that the UV NMI was captured by some other NMI handler and then either ignored or mistakenly processed as a perf event. We set a per_cpu ('ping') flag for those CPUs that ignored the initial NMI, and then send them an IPI NMI signal. The NMI_LOCAL handler on each cpu does not need to read the MMR, but instead checks the in memory flag indicating it was pinged. There are two module variables, 'ping_count' indicating how many requested NMI events occurred, and 'ping_misses' indicating how many stray NMI events. These most likely are perf events so it shows the overhead of the perf NMI interrupts and how many MMR reads were avoided. This patch also minimizes the reads of the MMRs by having the first cpu entering the NMI handler on each node set a per HUB in-memory atomic value. (Having a per HUB value avoids sending lock traffic over NumaLink.) Both types of UV NMIs from the SMI layer are supported. Signed-off-by: Mike Travis <travis@sgi.com> Reviewed-by: Dimitri Sivanich <sivanich@sgi.com> Reviewed-by: Hedi Berriche <hedi@sgi.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net> Cc: Jason Wessel <jason.wessel@windriver.com> Link: http://lkml.kernel.org/r/20130923212500.353547733@asylum.americas.sgi.com Signed-off-by: Ingo Molnar <mingo@kernel.org>		2013-09-24 09:02:02 +02:00
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asm	x86/UV: Update UV support for external NMI signals	2013-09-24 09:02:02 +02:00
uapi/asm	kvm uapi: Add KICK_CPU and PV_UNHALT definition to uapi	2013-08-26 12:46:01 +03:00