Processor Assisted Virtualization

[shankar.viswan-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org (Shankar Viswanathan)]

On Sun, Apr 19, 2009 at 11:00 AM, Jerry Feldman <gaf-mNDKBlG2WHs at public.gmane.org> wrote:
> I had read that most BIOS's have it disabled by default. Mine is a Tyan
> S2915 MB with an AMQ Opteron Quad Core. I don't do much with Windows, but I
> have Vista and XP VMs in the few cases I might need to use them.

Several BIOSes have it disabled by default because of concerns with
the so-called "Blue Pill":
http://theinvisiblethings.blogspot.com/2007/08/virtualization-detection-vs-blue-pill.html

AMD chips of the Barcelona or Shanghai generations (Phenom, Phenom II,
newer dual and quad-core Opterons etc.) are especially good at
virtualization since they have nested-paging enabled in hardware
(marketing term is "Rapid Virtualization Index"). This significantly
speeds up handling of page faults and virtual memory in general, so it
is a shame to not enable these features in the BIOS.

-Shankar

>
> On 04/19/2009 10:26 AM, Dan Ritter wrote:
>>
>> On Sun, Apr 19, 2009 at 08:15:18AM -0400, Jerry Feldman wrote:
>>
>>>
>>> The other night I noticed that the "Processor Assisted Virtualization"
>>> was disabled in my BIOS (it was hard to find, and I was looking for
>>> something else).
>>> Question, since I use KVM/QEMU and have an AMD Operon with the SVM flag,
>>> does KVM/QEMU automatically detect this, or is there something I need to do
>>> to tell the software that Hardware VM is activated.
>>>
>>
>> Loading the kvm-amd module should be done automatically by
>> kvm/qemu, and it will tell you if it can't.
>>
>> Normally Intel has a BIOS setting to turn it on/off, and AMD
>> machines just leave it on all the time. Since there is no
>> performance hit to turn it off, I am irked at Intel.
>>
>> I am also irked at HP, who has managed to include such a BIOS
>> setting for AMD machines and defaults it to off. None of my
>> other AMD motherboards requires such a change.
>>
>>
>
>
> --
> Jerry Feldman <gaf-mNDKBlG2WHs at public.gmane.org>
> Boston Linux and Unix
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