[fedora-virt] intel vt versus amd-v?

Richard W.M. Jones rjones at redhat.com
Fri Jun 5 20:41:54 UTC 2009

On Fri, Jun 05, 2009 at 04:21:00PM -0400, Robert P. J. Day wrote:
> On Fri, 5 Jun 2009, Richard W.M. Jones wrote:
> > On Fri, Jun 05, 2009 at 11:57:14AM -0400, Robert P. J. Day wrote:
> > >   a friend wants to buy a server (probably dell) with HW virt support,
> > > and is wondering if there are any current clear advantages of intel
> > > over amd.  the only observation i had time to make was that, if one
> > > checks out entry-level servers from dell (ballpark $1000 cdn), the amd
> > > opteron systems appear to be somewhat less expensive than equivalent
> > > intel-based systems.
> > >
> > >   further thoughts?
> >
> > The more recent Intel and AMD parts have extra virtualization
> > features which make virtualization more efficient -- primarily Intel
> > Extended Page Tables (EPT) and AMD Nested Page Tables (NPT).  So
> > your friend should look at the chips which support that, basically
> > Intel Nehalem and the quad-core AMD Opterons (previously known as
> > Barcelona).
>   NPT is what AMD is now calling "Rapid Virtualization Indexing", yes?

I haven't heard it called that til now, but it does look like
their marketing name for NPT, yes.

BTW(1) some AMD machines need to have virtualization enabled in
the BIOS.

BTW(2) to decode the /proc/cpuinfo flags, look here:
EPT is a flag, but NPT isn't (you have to look in the kernel messages
when loading the KVM module to see if NPT is supported).


Richard Jones, Emerging Technologies, Red Hat  http://et.redhat.com/~rjones
Read my programming blog: http://rwmj.wordpress.com
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