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



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.

s/fucntionality/functionality

> 
> This patch is based on qemu commit 904d6f588063fb5ad2b61998acdf1e73fb4
> 
> The rate limiting is exported in the XML as:
> <devices>
>   ...
>   <rng model='virtio'>
>     <rate period='1234'>4321</rate>
>     <backend model='random'/>
>   </rng>
>   ...
> ---
>  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;devices&gt;
>      &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>
>          </ul>
>        </dd>
> +      <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?

>        <dt><code>backend</code></dt>
>        <dd>
>          <p>
> diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng
> index 8330a50..da53095 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>
> 
> @@ -3546,6 +3551,17 @@
>      </element>
>    </define>
> 
> +  <define name="rng-rate">
> +    <element name="rate">
> +      <optional>
> +        <attribute name="period">
> +          <ref name="positiveInteger"/>
> +        </attribute>
> +      </optional>
> +      <ref name="positiveInteger"/>
> +    </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 53c6b2f..023e92c 100644
> --- a/src/conf/domain_conf.c
> +++ b/src/conf/domain_conf.c
> @@ -7445,6 +7445,17 @@ virDomainRNGDefParseXML(const xmlNodePtr node,
> 
>      ctxt->node = node;
> 
> +    if (virXPathUInt("string(./rate)", ctxt, &def->rate) < -1) {
> +        virReportError(VIR_ERR_XML_ERROR, "%s", _("invalid RNG rate value"));
> +        goto error;
> +    }
> +
> +    if (def->rate > 0 &&
> +        virXPathUInt("string(./rate/@period)", ctxt, &def->period) < -1) {
> +        virReportError(VIR_ERR_XML_ERROR, "%s", _("invalid RNG period value"));
> +        goto error;
> +    }
> +
>      if ((nbackends = virXPathNodeSet("./backend", ctxt, &backends)) < 0)
>          goto error;
> 
> @@ -13792,6 +13803,12 @@ virDomainRNGDefFormat(virBufferPtr buf,
>      const char *backend = virDomainRNGBackendTypeToString(def->backend);
> 
>      virBufferAsprintf(buf, "    <rng model='%s'>\n", model);
> +    if (def->rate) {
> +        virBufferAddLit(buf, "      <rate");
> +        if (def->period)
> +            virBufferAsprintf(buf, " period='%u'", def->period);
> +        virBufferAsprintf(buf, ">%u</rate>\n", def->rate);
> +    }
>      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 b78a04c..b34484c 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;
> +    unsigned int period;
> 
>      union {
>          char *file; /* file name for 'random' source */
> diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
> index d3a9b70..14d8f6d 100644
> --- a/src/qemu/qemu_command.c
> +++ b/src/qemu/qemu_command.c
> @@ -4297,6 +4297,14 @@ 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 4611ae5..428804b 100644
> --- a/tests/qemuxml2argvdata/qemuxml2argv-virtio-rng-random.args
> +++ b/tests/qemuxml2argvdata/qemuxml2argv-virtio-rng-random.args
> @@ -1 +1 @@
> -LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test /usr/bin/qemu -S -M pc -m 214 -smp 1 -nographic -nodefaults -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=/test/phile -device virtio-rng-pci,rng=rng0,bus=pci.0,addr=0x4
> +LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test /usr/bin/qemu -S -M pc -m 214 -smp 1 -nographic -nodefaults -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=/test/phile -device virtio-rng-pci,rng=rng0,max-bytes=1337,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 ab1f38c..73e77cd 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 period='1234'>1337</rate>
>        <backend model='random'>/test/phile</backend>
>      </rng>
>    </devices>
> 


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