Re: [libvirt] [PATCH 3/4] 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 fucntionality.

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 ... &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; @@ -4316,6 +4317,15 @@ 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 element 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 period is represented in miliseconds.

+ The default period is 1000ms or 1 second.

+++ b/src/conf/domain_conf.h @@ -1736,6 +1736,8 @@ enum virDomainRNGBackend { struct _virDomainRNGDef { int model; int backend; + unsigned int rate; + unsigned int period;

+++ 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

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>