[libvirt] [PATCH] docs: add a mention for start a vm with rawio = 'yes'

[Luyao Huang]

When we start a vm which have rawio = 'yes' settings without
any file caps settings for qemu, qemu process still cannot use
this caps (CAP_SYS_RAWIO) and the /proc/pidofqemu/status like
this:

  CapInh: 0000000000020000
  CapPrm: 0000000000000000
  CapEff: 0000000000000000
  CapBnd: 0000001fffffffff

this is because we do not set file caps for qemu (see man 7
capabilities), although laine have mentioned this in commit
e11451, i think it will be good if we add this in docs.

Signed-off-by: Luyao Huang <lhuang at redhat.com>
---
 docs/formatdomain.html.in | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
index fb0a0d1..2bcb59d 100644
--- a/docs/formatdomain.html.in
+++ b/docs/formatdomain.html.in
@@ -1886,7 +1886,10 @@
             than that (per-process basis, affects all the domain disks).
             To confine the capability as much as possible for QEMU driver
             as this stage, <code>sgio</code> is recommended, it's more
-            secure than <code>rawio</code>.
+            secure than <code>rawio</code>. If you really want use rawio
+            = 'yes', please also add file caps for qemu (like this
+            'setcap "cap_sys_rawio+ie" /usr/libexec/qemu-kvm', for more details
+            please see capabilities(7)).
             </dd>
           <dt><code>sgio</code> attribute
           <span class="since">since 1.0.2</span></dt>
-- 
1.8.3.1