perf/x86/ibs: Fix race with IBS_STARTING state
While tracing the IBS bits I saw the NMI hitting between clearing IBS_STARTING and the actual MSR writes to disable the counter. Since IBS_STARTING was cleared, the handler assumed these were spurious NMIs and because STOPPING wasn't set yet either, insta-triggered an "Unknown NMI". Cure this by clearing IBS_STARTING after disabling the hardware. Tested-by: NBorislav Petkov <bp@suse.de> Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: David Ahern <dsahern@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Signed-off-by: NIngo Molnar <mingo@kernel.org>
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