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From Pierre-Luc Dion <>
Subject [XenServer] meltdown-spectre
Date Tue, 09 Jan 2018 02:32:48 GMT

>From recent blog post, I've read that system using full virtualization such
as KVM, VMware or Xen-HVM are not affected?  Anyhow, from the latest hotfix
of XenServer 7.1cu1 hf8, it look like they systematically convert VM from
PV to HVM, so in the case of a VM stop/start by CloudStack, a PV vm would
be restarted as HVM.

Look like this could be problematic if your VM kernel does not support
both, we've just starting tested and so far look like our Debian systemvm
template work fine, it can be created as HVM.

Another point is that Citrix released an hotfix for xs7.2, 7.3 but not for
7.1, you need to cumulative update to remain on 7.1 which is LTS.

And last, does anyone did some benchmark before and after the kernel fix
for Meltdown ?  Some report state 30-35% cpu usage increase (not hypervisor
specific) and  Lucian [1] might indicate it would depend on the cpu model.
Any metrics to share ?  We are doing some tests on our side we should be
able to share some stuff soon...



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