docs: change the minimum weight description for blkio

Since 2.6.39, kernel changed the minimum weight of device blkio.
Update related docs.
Signed-off-by: NGao feng <gaofeng@cn.fujitsu.com>
Signed-off-by: NChen Hanxiao <chenhanxiao@cn.fujitsu.com>

docs/formatdomain.html.in

@@ -772,7 +772,8 @@
       <dt><code>weight</code></dt>
       <dd> The optional <code>weight</code> element is the overall I/O
         weight of the guest. The value should be in the range [100,
-        1000].</dd>
+        1000]. After kernel 2.6.39, the value could be in the
+        range [10, 1000].</dd>
       <dt><code>device</code></dt>
       <dd>The domain may have multiple <code>device</code> elements
         that further tune the weights for each host block device in
@@ -789,7 +790,8 @@
         mandatory sub-elements, <code>path</code> describing the
         absolute path of the device, and <code>weight</code> giving
         the relative weight of that device, in the range [100,
-        1000].  <span class="since">Since 0.9.8</span></dd>
+        1000]. After kernel 2.6.39, the value could be in the
+        range [10, 1000].<span class="since">Since 0.9.8</span></dd>
     </dl>
 
 

tools/virsh.pod

@@ -1629,14 +1629,15 @@ Specifying -1 as a value for these limits is interpreted as unlimited.
 [I<--live>] | [I<--current>]]
 
 Display or set the blkio parameters. QEMU/KVM supports I<--weight>.
-I<--weight> is in range [100, 1000].
+I<--weight> is in range [100, 1000]. After kernel 2.6.39, the value
+could be in the range [10, 1000].
 
 B<device-weights> is a single string listing one or more device/weight
 pairs, in the format of /path/to/device,weight,/path/to/device,weight.
-Each weight is in the range [100, 1000], or the value 0 to remove that
-device from per-device listings.  Only the devices listed in the string
-are modified; any existing per-device weights for other devices remain
-unchanged.
+Each weight is in the range [100, 1000], [10, 1000] after kernel 2.6.39,
+or the value 0 to remove that device from per-device listings.
+Only the devices listed in the string are modified;
+any existing per-device weights for other devices remain unchanged.
 
 If I<--live> is specified, affect a running guest.
 If I<--config> is specified, affect the next boot of a persistent guest.