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authorDavid Ahern <dsahern@gmail.com>2012-09-13 14:59:13 -0600
committerArnaldo Carvalho de Melo <acme@redhat.com>2012-10-16 12:43:31 -0300
commit1342798cc13e3b48d9b5738f0c8fa812ccea8101 (patch)
tree19a89b595304ab6e2bf5ecc969599f9585bcc15a /tools
parent95cf59ea72331d0093010543b8951bb43f262cac (diff)
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 <dsahern@gmail.com> Acked-by: Peter Zijlstra <peterz@infradead.org> Acked-by: Robert Richter <robert.richter@amd.com> Tested-by: Robert Richter <robert.richter@amd.com> Reviewed-by: Robert Richter <robert.richter@amd.com> Cc: Avi Kivity <avi@redhat.com> Cc: Gleb Natapov <gleb@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Robert Richter <robert.richter@amd.com> Link: http://lkml.kernel.org/r/1347569955-54626-2-git-send-email-dsahern@gmail.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools')
-rw-r--r--tools/perf/util/parse-events.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index aed38e4b9df..75c7b0fca6d 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;