Messages in this thread Patch in this message | | | From | Arnaldo Carvalho de Melo <> | Subject | [PATCH 01/11] perf tool: Precise mode requires exclude_guest | Date | Wed, 17 Oct 2012 14:19:37 -0300 |
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From: David Ahern <dsahern@gmail.com>
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> --- tools/perf/util/parse-events.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-)
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c index aed38e4..75c7b0f 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; -- 1.7.1
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