From 1342798cc13e3b48d9b5738f0c8fa812ccea8101 Mon Sep 17 00:00:00 2001 From: David Ahern Date: Thu, 13 Sep 2012 14:59:13 -0600 Subject: [PATCH] perf tool: Precise mode requires exclude_guest Summary of events per Peter: "Intel PEBS in VT-x context uses the DS address as a guest linear address, even though its programmed by the host as a host linear address. This either results in guest memory corruption and or the hardware faulting and 'crashing' the virtual machine. Therefore we have to disable PEBS on VT-x enter and re-enable on VT-x exit, enforcing a strict exclude_guest. AMB IBS does work but doesn't currently support exclude_* at all, setting an exclude_* bit will make it fail." This patch handles userspace perf command, setting the exclude_guest attribute if precise mode is requested, but only if a user has not specified a request for guest or host only profiling (G or H attribute). Kernel side AMD currently ignores all exclude_* bits, so there is no impact to existing IBS code paths. Robert Richter has a patch where IBS code will return EINVAL if an exclude_* bit is set. When this goes in it means use of :p on AMD with IBS will first fail with EINVAL (because exclude_guest will be set). Then the existing fallback code within perf will unset exclude_guest and try again. The second attempt will succeed if the CPU supports IBS profiling. Signed-off-by: David Ahern Acked-by: Peter Zijlstra Acked-by: Robert Richter Tested-by: Robert Richter Reviewed-by: Robert Richter Cc: Avi Kivity Cc: Gleb Natapov Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Robert Richter Link: http://lkml.kernel.org/r/1347569955-54626-2-git-send-email-dsahern@gmail.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/parse-events.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c index aed38e4b9dfa..75c7b0fca6d9 100644 --- a/tools/perf/util/parse-events.c +++ b/tools/perf/util/parse-events.c @@ -690,6 +690,9 @@ static int get_event_modifier(struct event_modifier *mod, char *str, eH = 0; } else if (*str == 'p') { precise++; + /* use of precise requires exclude_guest */ + if (!exclude_GH) + eG = 1; } else break; -- GitLab