No 64-bit guest support for inside a 64-bit host

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No 64-bit guest support for inside a 64-bit host

Postby devsk » 17. Sep 2008, 06:37

I have what looks like a 64-bit install (under Gentoo Linux) on a 64-bit host:
# file /opt/VirtualBox/VirtualBox
/opt/VirtualBox/VirtualBox: setuid ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.4.0, stripped

# uname -m
x86_64

# /opt/VirtualBox/VirtualBox --help
Sun xVM VirtualBox Graphical User Interface 2.0.2

But when I try to boot a x86_64 livecd, the boot process says it needs a 64-bit machine but found only i586. Do I need to do something special to get 64-bit guest to run on a 64-bit host.
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Postby TerryE » 17. Sep 2008, 07:27

OK but read the other posts on this (i) what actual CPU chipset do you have? Some especially the earlier low-end ones do not have VT-x or AMD-V support. (ii) Have you enabled virtualisation support inside your BIOS? If the BIOS turns this off, then just like a guest 64bit OS, this isn't available.
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Postby devsk » 17. Sep 2008, 08:15

TerryE wrote:OK but read the other posts on this (i) what actual CPU chipset do you have? Some especially the earlier low-end ones do not have VT-x or AMD-V support. (ii) Have you enabled virtualisation support inside your BIOS? If the BIOS turns this off, then just like a guest 64bit OS, this isn't available.
You mean I need VT-x or AMD-V to get 64-bit guest support? That's a bit strange requirement. I have a 64-bit amd64 3800 X2 cpu and no AMD-V. That means I am out of luck with 64-bit guest support. The documentation doesn't seem to mention this fine point about 64-bit guest support.
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Postby Nille02 » 17. Sep 2008, 11:36

devsk wrote:You mean I need VT-x or AMD-V to get 64-bit guest support?

Yes
devsk wrote:That's a bit strange requirement.

No

devsk wrote:I have a 64-bit amd64 3800 X2 cpu and no AMD-V. That means I am out of luck with 64-bit guest support. The documentation doesn't seem to mention this fine point about 64-bit guest support.


The Athlon X2 series has AMD-V look in your BIOS. Many OEMs has Deaktivate this CPU Feature by Default.

Next you need to Aktivate ACPI, IOACPI, PAE/NX and AMD-V/VT-x

PS: Some Informations about AMD-V http://en.wikipedia.org/wiki/AMD-V
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Postby devsk » 17. Sep 2008, 18:38

The Athlon X2 series has AMD-V look in your BIOS. Many OEMs has Deaktivate this CPU Feature by Default.

I know my AMD 3800 X2 doesn't have pacifica extension. But it is 64-bit CPU.

AMD-V is a strange requirement for 64-bit guest support. I see no technical reason for making the 64-bit guest support depend on that extension and proof of that is VMWare. VMWare doesn't have this requirement. It even supports 64-bit guest on a 32-bit host on a CPU which has native 64-bit support.
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Postby TerryE » 17. Sep 2008, 18:54

sorry but VMware does have this requirement, though it does as you say you can virtualize 64-bit OSs from a 32bit one. google vmware pdf amd-v terrye site:forums.virtualbox.org if you want to read some of my earlier discussions on this.
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Postby devsk » 17. Sep 2008, 19:21

OK. I don't know what that means. I have already mentioned that my CPU doesn't have Pacifica extension.

I can run 64-bit guest on a 32-bit host on my desktop under VMWare. I cannot run 64-bit guest on a 64-bit host on the same desktop under VirtualBox. So, how is the 64-bit guest support same? VMWare doesn't require AMD-V. It CAN use it.

Anyway, I read the requirement list from virtualbox manual again: 3. You must enable hardware virtualization; software virtualization is not supported for 64-bit VMs, which means that no 64-bit guest support if I don't have hardware virtualization. That's a shame because I was waiting for 64-bit guest support for some time now.
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Postby TerryE » 17. Sep 2008, 20:13

If you are saying that you can run a 64bit guest OS under your 32 bit OS on an AMD64 non AMD-V cpu then I am surprised but I won't argue. It is technically possible to employ the same non VT-x software recompilation/patching techniques that both VMare and VBox use for 32bit non-H/W assist CPUs. It's just a lot of work to do this and Sun have decided not to do this for VBox. You'll just have to use VMware.
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Postby devsk » 17. Sep 2008, 21:27

We can probably mention this thread in the FAQs because there seems to be confusion about this. People mistakenly assume that now virtualbox is a replacement for vmware but the important caveat is the hardware support it needed.
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Postby TerryE » 18. Sep 2008, 01:04

devsk wrote:We can probably mention this thread in the FAQs because there seems to be confusion about this.
Sighh. See the Forum FAQ. This answer is given to the first question already. :roll:
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