[patch] perf_event_open.2: Exclude_host/exclude_guest clarification

[Vince Weaver]

This patch relates to the exclude_host and exclude_guest bits added 
by the  following commit:

   exclude_host, exclude_guest; Linux 3.2
        commit a240f76165e6255384d4bdb8139895fac7988799
        Author: Joerg Roedel <joerg.roedel@xxxxxxx>
        Date:   Wed Oct 5 14:01:16 2011 +0200

            perf, core: Introduce attrs to count in either host or guest mode

            Signed-off-by: Joerg Roedel <joerg.roedel@xxxxxxx>
            Signed-off-by: Gleb Natapov <gleb@xxxxxxxxxx>
            Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
            Link: http://lkml.kernel.org/r/1317816084-18026-2-git-send-email-gleb@xxxxxxxxxx
            Signed-off-by: Ingo Molnar <mingo@xxxxxxx>

The updated manpage text clarifies that the "exclude_host" and
"exclude_guest" perf_event_open() attr bits only apply in the 
context of a KVM environment and are currently x86 only.

This is a resend of the patch; the previous time I sent it
(http://thread.gmane.org/gmane.linux.man/7500) it did not
receive any comments.

Signed-off-by: Vince Weaver <vincent.weaver@xxxxxxxxx>

diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2
index 39c8d8c..1ea56c9 100644
--- a/man2/perf_event_open.2
+++ b/man2/perf_event_open.2
@@ -1006,11 +1006,25 @@ struct sample_id {
 .TP
 .IR "exclude_host" " (since Linux 3.2)"
 .\" commit a240f76165e6255384d4bdb8139895fac7988799
-Do not measure time spent in VM host.
+When conducting measurements that include processes running
+VM instances (i.e. have executed a
+.I KVM_RUN
+.BR ioctl (2)
+) only measure events happening inside a guest instance.
+This is only meaningful outside the guests; this setting does
+not change counts gathered inside of a guest.
+Currently this functionality is x86 only.
 .TP
 .IR "exclude_guest" " (since Linux 3.2)"
 .\" commit a240f76165e6255384d4bdb8139895fac7988799
-Do not measure time spent in VM guest.
+When conducting measurements that include processes running
+VM instances (i.e. have executed a
+.I KVM_RUN
+.BR ioctl (2)
+) do not measure events happening inside guest instances.
+This is only meaningful outside the guests; this setting does
+not change counts gathered inside of a guest.
+Currently this functionality is x86 only.
 .TP
 .IR "exclude_callchain_kernel" " (since Linux 3.7)"
 .\" commit d077526485d5c9b12fe85d0b2b3b7041e6bc5f91
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