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