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Re: [libvirt] [PATCH 7/6] virtio-rng: Add rate limiting options for virtio-RNG

On 02/19/13 14:21, John Ferlan wrote:
On 02/13/2013 11:28 AM, Peter Krempa wrote:
Qemu's implementation of virtio RNG supports rate limiting of the
entropy used. This patch exposes the option to tune this fucntionality.


This patch is based on qemu commit 904d6f588063fb5ad2b61998acdf1e73fb4

The rate limiting is exported in the XML as:
   <rng model='virtio'>
     <rate period='1234'>4321</rate>
     <backend model='random'/>
  docs/formatdomain.html.in                              |  9 +++++++++
  docs/schemas/domaincommon.rng                          | 18 +++++++++++++++++-
  src/conf/domain_conf.c                                 | 17 +++++++++++++++++
  src/conf/domain_conf.h                                 |  2 ++
  src/qemu/qemu_command.c                                |  8 ++++++++
  .../qemuxml2argv-virtio-rng-random.args                |  2 +-
  .../qemuxml2argv-virtio-rng-random.xml                 |  1 +
  7 files changed, 55 insertions(+), 2 deletions(-)

diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
index e8cd086..b264460 100644
--- a/docs/formatdomain.html.in
+++ b/docs/formatdomain.html.in
@@ -4293,6 +4293,7 @@ qemu-kvm -net nic,model=? /dev/null
      &lt;rng model='virtio'&gt;
+      &lt;rate period="2000"&gt;1234&lt;/rate&gt;
        &lt;backend model='random'&gt;/dev/random&lt;/backend&gt;
        &lt;!-- OR --&gt;
        &lt;backend model='egd' type='udp'&gt;
@@ -4315,6 +4316,14 @@ qemu-kvm -net nic,model=? /dev/null
            <li>'virtio' &mdash; supported by qemu and virtio-rng kernel module</li>
+      <dt><code>rate</code></dt>
+      <dd>
+        <p>
+          The rate parameter allows to limit the rate that the entropy can be
+          read from the source. The value is in bits that the device is allowed
+          to read in the selected period. The default period is 1000ms or 1 second.
+        </p>
+      </dd>

bits or bytes?

qemu uses bits for it's configuration value. As the expected data rades are pretty low, I think bits can be used and potentially divided to larger values if needed.


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