Re: Efficacy of jitterentropy RNG on qemu-kvm Guests

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Fri, Aug 10, 2018 at 08:33:00PM +0000, procmem wrote:
> Hello. I'm a distro maintainer and was wondering about the efficacy of
> entropy daemons like haveged and jitterentropyd in qemu-kvm. One of the
> authors of haveged [0] pointed out if the hardware cycles counter is
> emulated and deterministic, and thus predictible. He therefore does not
> recommend using HAVEGE on those systems. Is this the case with KVM's
> counters?
> 
> PS. I will be setting VM CPU settings to host-passthrough.

Hardware from circa 2011 onwards has RDRAND support, and with host-passthrough
this will be available to the guest.  The rngd daemon, running in the guest,
can use this as a source to feed the kernel entropy.

In addition QEMU has support for virtio-rng which can pull entropy from
/dev/urandom on the host, and feed it into the guest, where again rngd can
give it to the kernel.

So why do you need to consider haveged / jitterentropyd at all with QEMU ?
It should suffice to just enable virtio-rng in the host and run rngd in
all guests. If the host has RDRAND, that's an extra bonus.

haveged / jitterentropyd should only be needed on other non-QEMU hypervisors
which don't support something equiv to virtio-rng, and are on hardware that
is too old for RDRAND.

Regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
|: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|

_______________________________________________
libvirt-users mailing list
libvirt-users@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/libvirt-users



[Index of Archives]     [Virt Tools]     [Lib OS Info]     [Fedora Users]     [Fedora Desktop]     [Fedora SELinux]     [Yosemite News]     [KDE Users]

  Powered by Linux