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 <dsah...@gmail.com> Cc: Ingo Molnar <mi...@kernel.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Robert Richter <robert.rich...@amd.com> Cc: Gleb Natapov <g...@redhat.com> Cc: Avi Kivity <a...@redhat.com> Link: https://lkml.org/lkml/2012/7/9/264 --- 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 44afcf4..696cc7e 100644 --- a/tools/perf/util/parse-events.c +++ b/tools/perf/util/parse-events.c @@ -694,6 +694,9 @@ 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; -- 1.7.10.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
