Update design.txt to reflect the presence of the exclude_host
and exclude_guest perf flags.

Signed-off-by: Andrew Murray <redacted>
---
 tools/perf/design.txt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/perf/design.txt b/tools/perf/design.txt
index a28dca2..7de7d83 100644
--- a/tools/perf/design.txt
+++ b/tools/perf/design.txt

@@ -222,6 +222,10 @@ The 'exclude_user', 'exclude_kernel' and 'exclude_hv' bits provide a
 way to request that counting of events be restricted to times when the
 CPU is in user, kernel and/or hypervisor mode.
 
+Furthermore the 'exclude_host' and 'exclude_guest' bits provide a way
+to request counting of events restricted to guest and host contexts when
+using virtualisation.