From: Peter Krempa <pkrempa@redhat.com>
Date: Wed, 13 Feb 2013 14:37:39 +0000 (+0100)
Subject: virtio-rng: Add rate limiting options for virtio-RNG
X-Git-Tag: v1.0.4-rc1~104
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=32bd699f5547841677608577a5c9c597ed0f6647;p=thirdparty%2Flibvirt.git

virtio-rng: Add rate limiting options for virtio-RNG

Qemu's implementation of virtio RNG supports rate limiting of the
entropy used. This patch exposes the option to tune this functionality.

This patch is based on qemu commit 904d6f588063fb5ad2b61998acdf1e73fb4

The rate limiting is exported in the XML as:
<devices>
  ...
  <rng model='virtio'>
    <rate bytes='123' period='1234'/>
    <backend model='random'/>
  </rng>
  ...
---

diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
index 35b47f2dd7..1ef80b06ca 100644
--- a/docs/formatdomain.html.in
+++ b/docs/formatdomain.html.in
@@ -4294,6 +4294,7 @@ qemu-kvm -net nic,model=? /dev/null
   ...
   &lt;devices&gt;
     &lt;rng model='virtio'&gt;
+      &lt;rate period="2000" bytes="1234"/&gt;
       &lt;backend model='random'&gt;/dev/random&lt;/backend&gt;
       &lt;!-- OR --&gt;
       &lt;backend model='egd' type='udp'&gt;
@@ -4316,6 +4317,18 @@ qemu-kvm -net nic,model=? /dev/null
           <li>'virtio' &mdash; supported by qemu and virtio-rng kernel module</li>
         </ul>
       </dd>
+      <dt><code>rate</code></dt>
+      <dd>
+        <p>
+          The optional <code>rate</code> element allows limiting the rate at
+          which entropy can be consumed from the source.  The mandatory
+          attribute <code>bytes</code> specifies how many bytes are permitted
+          to be consumed per period.  An optional <code>period</code> attribute
+          specifies the duration of a period in milliseconds; if omitted, the
+          period is taken as 1000 milliseconds (1 second).
+          <span class='since'>Since 1.0.4</span>
+        </p>
+      </dd>
       <dt><code>backend</code></dt>
       <dd>
         <p>
diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng
index c40263c76b..97920653df 100644
--- a/docs/schemas/domaincommon.rng
+++ b/docs/schemas/domaincommon.rng
@@ -3522,7 +3522,12 @@
           <value>virtio</value>
         </choice>
       </attribute>
-      <ref name="rng-backend"/>
+      <interleave>
+        <ref name="rng-backend"/>
+        <optional>
+          <ref name="rng-rate"/>
+        </optional>
+      </interleave>
     </element>
   </define>
 
@@ -3550,6 +3555,20 @@
     </element>
   </define>
 
+  <define name="rng-rate">
+    <element name="rate">
+      <attribute name="bytes">
+        <ref name="positiveInteger"/>
+      </attribute>
+      <optional>
+        <attribute name="period">
+          <ref name="positiveInteger"/>
+        </attribute>
+      </optional>
+      <empty/>
+    </element>
+  </define>
+
   <define name="usbmaster">
     <element name="master">
       <attribute name="startport">
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 95d2ff22b8..3278e9c15e 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -7570,6 +7570,19 @@ virDomainRNGDefParseXML(const xmlNodePtr node,
 
     ctxt->node = node;
 
+    if (virXPathUInt("string(./rate/@bytes)", ctxt, &def->rate) < -1) {
+        virReportError(VIR_ERR_XML_ERROR, "%s",
+                       _("invalid RNG rate bytes value"));
+        goto error;
+    }
+
+    if (def->rate > 0 &&
+        virXPathUInt("string(./rate/@period)", ctxt, &def->period) < -1) {
+        virReportError(VIR_ERR_XML_ERROR, "%s",
+                       _("invalid RNG rate period value"));
+        goto error;
+    }
+
     if ((nbackends = virXPathNodeSet("./backend", ctxt, &backends)) < 0)
         goto error;
 
@@ -13897,6 +13910,12 @@ virDomainRNGDefFormat(virBufferPtr buf,
     const char *backend = virDomainRNGBackendTypeToString(def->backend);
 
     virBufferAsprintf(buf, "    <rng model='%s'>\n", model);
+    if (def->rate) {
+        virBufferAsprintf(buf, "      <rate bytes='%u'", def->rate);
+        if (def->period)
+            virBufferAsprintf(buf, " period='%u'", def->period);
+        virBufferAddLit(buf, "/>\n");
+    }
     virBufferAsprintf(buf, "      <backend model='%s'", backend);
 
     switch ((enum virDomainRNGBackend) def->backend) {
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index 0fe43c5869..96f11ba76d 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -1736,6 +1736,8 @@ enum virDomainRNGBackend {
 struct _virDomainRNGDef {
     int model;
     int backend;
+    unsigned int rate; /* bytes per period */
+    unsigned int period; /* milliseconds */
 
     union {
         char *file; /* file name for 'random' source */
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index e7f232579a..78c5cfc4f5 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -4492,6 +4492,14 @@ qemuBuildRNGDeviceArgs(virCommandPtr cmd,
 
     virBufferAsprintf(&buf, "virtio-rng-pci,rng=%s", dev->info.alias);
 
+    if (dev->rate > 0) {
+        virBufferAsprintf(&buf, ",max-bytes=%u", dev->rate);
+        if (dev->period)
+            virBufferAsprintf(&buf, ",period=%u", dev->period);
+        else
+            virBufferAddLit(&buf, ",period=1000");
+    }
+
     if (qemuBuildDeviceAddressStr(&buf, &dev->info, qemuCaps) < 0)
         goto cleanup;
 
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-virtio-rng-random.args b/tests/qemuxml2argvdata/qemuxml2argv-virtio-rng-random.args
index 7ab9dbc0c0..5d296e825e 100644
--- a/tests/qemuxml2argvdata/qemuxml2argv-virtio-rng-random.args
+++ b/tests/qemuxml2argvdata/qemuxml2argv-virtio-rng-random.args
@@ -3,4 +3,4 @@ LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test /usr/bin/qemu \
 -monitor unix:/tmp/test-monitor,server,nowait -no-acpi -boot c -usb \
 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3 \
 -object rng-random,id=rng0,filename=/dev/hwrng \
--device virtio-rng-pci,rng=rng0,bus=pci.0,addr=0x4
+-device virtio-rng-pci,rng=rng0,max-bytes=123,period=1234,bus=pci.0,addr=0x4
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-virtio-rng-random.xml b/tests/qemuxml2argvdata/qemuxml2argv-virtio-rng-random.xml
index 1e2c4be95a..354ae42932 100644
--- a/tests/qemuxml2argvdata/qemuxml2argv-virtio-rng-random.xml
+++ b/tests/qemuxml2argvdata/qemuxml2argv-virtio-rng-random.xml
@@ -17,6 +17,7 @@
     <controller type='usb' index='0'/>
     <memballoon model='virtio'/>
     <rng model='virtio'>
+      <rate bytes='123' period='1234'/>
       <backend model='random'>/dev/hwrng</backend>
     </rng>
   </devices>