[PATCH] docs/system/arm/virt.rst: Add note on CPU features off by default

[Gustavo Romero]

Add a note on CPU features off by default on `virt` machines. These CPU
features will remain off even if `-cpu max` is given so the user must
turn on them explicitly on `virt` machines.

Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org>
---
 docs/system/arm/virt.rst | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/docs/system/arm/virt.rst b/docs/system/arm/virt.rst
index c245c52b7a..0e9ad526b4 100644
--- a/docs/system/arm/virt.rst
+++ b/docs/system/arm/virt.rst
@@ -69,6 +69,17 @@ Supported guest CPU types:
 Note that the default is ``cortex-a15``, so for an AArch64 guest you must
 specify a CPU type.
 
+Also, please note that passing ``max`` CPU (i.e. ``-cpu max``) won't
+enable all the CPU features for a given ``virt`` machine. Some CPU
+features are ``off`` by default (e.g. MTE) -- see machine-specific list
+below or check them for a given machine passing ``help``. For instance,
+for the ``virt`` machine pass ``-machine virt,help`` to QEMU.
+
+For example, because MTE CPU feature is ``off`` by default it's
+necessary to turn  MTE ``on`` explicitly to have this CPU feature
+available on the ``virt`` machine, even when ``max`` CPU is specified:
+``-machine virt,mte=on -cpu max`` .
+
 Graphics output is available, but unlike the x86 PC machine types
 there is no default display device enabled: you should select one from
 the Display devices section of "-device help". The recommended option
-- 
2.34.1