On 02/25/2013 03:31 PM, 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>
> ...
> ---
>
> Notes:
> This series would benefit from the per-driver XML parsing checks to verify
> that rate > 8bits, otherwise it will be rounded down to 0 bytes. I will
> follow up with that change as soon as the per-driver callbacks get in.
>
> Version 3:
> - State the time unit in docs
> Version 2:
> - Qemu uses bytes/period, adapt the value according to that
>
> docs/formatdomain.html.in | 10 ++++++++++
> docs/schemas/domaincommon.rng | 18 +++++++++++++++++-
> src/conf/domain_conf.c | 17 +++++++++++++++++
> src/conf/domain_conf.h | 2 ++
> src/qemu/qemu_command.c | 9 +++++++++
> .../qemuxml2argv-virtio-rng-random.args | 2 +-
> .../qemuxml2argv-virtio-rng-random.xml | 1 +
> 7 files changed, 57 insertions(+), 2 deletions(-)
>
> diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
> index 2a60f61..220884c 100644
> --- a/docs/formatdomain.html.in
> +++ b/docs/formatdomain.html.in
> @@ -4294,6 +4294,7 @@ qemu-kvm -net nic,model=? /dev/null
> ...
> <devices>
> <rng model='virtio'>
> + <rate period="2000">1234</rate>
> <backend model='random'>/dev/random</backend>
> <!-- OR -->
> <backend model='egd' type='udp'>
> @@ -4316,6 +4317,15 @@ qemu-kvm -net nic,model=? /dev/null
> <li>'virtio' — supported by qemu and virtio-rng kernel module</li>
> </ul>
> </dd>
> + <dt><code>rate</code></dt>
> + <dd>
> + <p>
> + The rate element allows to limit the rate that the entropy can be
grammar doesn't quite flow here; see below
> + read from the source. The value is in bits that the device is allowed
> + to read in the selected period. The period is represented in miliseconds.
s/miliseconds/milliseconds/
> + The default period is 1000ms or 1 second.
I'm still not sure we accurately covered things. Maybe:
The optional <code>rate</code> element allows limiting the rate at which
entropy can be consumed from the source. 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). The element contents specify how many bits are permitted per
period. Drivers may enforce a minimum rate, and may round the rate down
to a minimum granularity.
> +++ b/src/conf/domain_conf.h
> @@ -1736,6 +1736,8 @@ enum virDomainRNGBackend {
> struct _virDomainRNGDef {
> int model;
> int backend;
> + unsigned int rate;
> + unsigned int period;
Comments here would help:
unsigned int rate; /* bits per period */
unsigned int period; /* milliseconds */
> +++ 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=100,period=1234,bus=pci.0,addr=0x4
This is a long line; please split it with a backslash-newline to fit in
80 columns.
> diff --git a/tests/qemuxml2argvdata/qemuxml2argv-virtio-rng-random.xml b/tests/qemuxml2argvdata/qemuxml2argv-virtio-rng-random.xml
> index ab1f38c..26ddd38 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'>800</rate>
> <backend model='random'>/test/phile</backend>
> </rng>
> </devices>
>
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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