perf, x86: Stop Intel PT before kdump starts

This patch stops Intel PT logging and saves its registers in memory
before kdump is started. This feature is needed to prevent Intel PT from
overwriting its log buffer after panic, and saved registers are needed to
find the last position where Intel PT wrote data.

After the crash dump is captured by kdump, users can retrieve the log buffer
from the vmcore and use it to investigate bad kernel behavior.

Signed-off-by: Takao Indoh <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Alexander Shishkin<[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: H.Peter Anvin <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vince Weaver <[email protected]>
Cc: Vivek Goyal <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

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