AMD Virtulization support

[johnc10]

Hi,
I have a new AMD64 X2 4200 AM2 but it doesn't appear to have AMD-V support. Checking the AMD website I can't find anything other than FX2 chips which state that have full virtualization support. Once article seemed to suggest x2 AM2 6000+ had it. Can anyone recommend a reasonably priced AM2 processor? The alternative is to pay more money for an Intel E6600 with IVT.

Thanks, John.

[deanjo]

Hi,
I have a new AMD64 X2 4200 AM2 but it doesn't appear to have AMD-V support. Checking the AMD website I can't find anything other than FX2 chips which state that have full virtualization support. Once article seemed to suggest x2 AM2 6000+ had it. Can anyone recommend a reasonably priced AM2 processor? The alternative is to pay more money for an Intel E6600 with IVT.

Thanks, John.

All AMD AM2 X2 processors feature AMD-V.

[johnc10]

I have an Asus M2N4-SLI and running FC6 Linux. The processor does not report it has AMD-V and therefore I cannot run full virtualisation. I've checked the BIOS for an option to turn it on but found nothing. AMD do not state my 4200 X2 processor supports AMD-V. The Intel Core 2 Duo does state IVT.

[Michael]

I have an Asus M2N4-SLI and running FC6 Linux. The processor does not report it has AMD-V and therefore I cannot run full virtualisation. I've checked the BIOS for an option to turn it on but found nothing. AMD do not state my 4200 X2 processor supports AMD-V. The Intel Core 2 Duo does state IVT.

Your processor should support AMD-V.

[deanjo]

I have an Asus M2N4-SLI and running FC6 Linux. The processor does not report it has AMD-V and therefore I cannot run full virtualisation. I've checked the BIOS for an option to turn it on but found nothing. AMD do not state my 4200 X2 processor supports AMD-V. The Intel Core 2 Duo does state IVT.

With AMD X2's there is no option to turn it on or off in the bios. It just stays on. It might be an issue with how your kernel or VM soution is compiled. VMWare for example does not support AMD-V or IVT until you are running Kernel 2.6.21 or greater that contain the necessary paravirt-ops extensions to Linux and you must be running VMWare Version 6.

[mlau]

With AMD X2's there is no option to turn it on or off in the bios. It just stays on.

I read on LKML that the behavior is inverse: the amd-v bit is
on by default and can only be switched OFF, no chance to enable
it again. The BIOS probably writes zeros to all unknown MSRs
and thereby accidentally disables AMD-V?

[johnc10]

Yes, it does have the svm flag after all (cat /proc/cpuinfo | grep svm). This site has a good intro.
http://www.crc.id.au/fedora-core-6-xen-and-asterisk/

My problem now is booting the xen kernel causes it to crash. It works on my other AMD64 X2 4200, but that is not AM2 so no svm flag :-(

[deanjo]

I read on LKML that the behavior is inverse: the amd-v bit is
on by default and can only be switched OFF, no chance to enable
it again. The BIOS probably writes zeros to all unknown MSRs
and thereby accidentally disables AMD-V?

I have yet to see this, despite setting up 100+ Amd servers using Xen.

I would be VERY interested if you can post me a link to the post on the LKML.

[mlau]

I would be VERY interested if you can post me a link to the post on the LKML.

Please don't take my word for it... I remember reading about this
when KVM first popped out of the woodwork and people started
to complain that their shiny new cpu wasn't supported. I do read
almost all LKML mail (I have much free time during compiler runs)
and I don't remember all details from things long past :)
(that sticky off bit then probably applies to the core2duo if
you have had no problems with amd64 so far. I *do* remember
someone mentioning that)

EDIT: found a reference to it in the xen lists; it definitely applies only
to Intel's vm extensions:
http://lists.xensource.com/archives/html/xen-devel/2006-06/msg00549.html