64 bit guest on 64 bit host (without VMX?)

This is for discussing general topics about how to use VirtualBox.

64 bit guest on 64 bit host (without VMX?)

Postby pwaller » 10. Mar 2009, 11:53

Hi,

I'm running on an Acer laptop, and unfortunately it seems (I understand after an exchange of e-mails with their exiguous support*) that Acer saw fit to disable VT-x in the BIOS and not provide an option to enable it. As far as I am aware this means that in order to enable this feature which the CPU does support, someone would have to reverse engineer the BIOS and prevent it from setting a single "lock-bit" with a WRMSR instruction.

Does this mean it is impossible to run a 64 bit guest without said BIOS hack? I seem to be experiencing a significant performance penalty running Ubuntu 32-bit under Vista 64-bit.

Thanks for any information.

* From Acer: "I understand what your [sic] saying but the BIOS will not support this software and as of yet there are no plans by ACER to release a BIOS update that will support the VT software"
pwaller
 
Posts: 5
Joined: 10. Mar 2009, 11:41

Re: 64 bit guest on 64 bit host (without VMX?)

Postby vbox4me2 » 10. Mar 2009, 12:23

Read the manual about 64bit guest support and a 32bit host.
As for the bios, have a look at http://www.coreboot.org/Welcome_to_coreboot
vbox4me2
Volunteer
 
Posts: 5222
Joined: 21. Nov 2008, 20:27
Location: Rotterdam

Re: 64 bit guest on 64 bit host (without VMX?)

Postby pwaller » 10. Mar 2009, 12:29

I saw this line in the manual:

"On 64-bit hosts, 64-bit guest support is always enabled, so you can simply install
a 64-bit operating system in the guest."

But when I try to start a 64-bit Ubuntu LiveCD on my 64-bit vista host, linux bails out complaining it only found an i686 CPU rather than a 64-bit one?

coreboot sounds nice but doesn't look like it comes close to supporting my machine..
pwaller
 
Posts: 5
Joined: 10. Mar 2009, 11:41

Re: 64 bit guest on 64 bit host (without VMX?)

Postby vbox4me2 » 10. Mar 2009, 12:44

See "1.6 64-bit guests" about the requirements, ea. "In detail, 64-bit guests are supported under the following conditions:", etc...
vbox4me2
Volunteer
 
Posts: 5222
Joined: 21. Nov 2008, 20:27
Location: Rotterdam

Re: 64 bit guest on 64 bit host (without VMX?)

Postby pwaller » 10. Mar 2009, 12:52

Sorry, I was confused by the manual for some reason. I thought that VMX was optional (as it says earlier in the manual), but I guess that is not the case for 64-bit OSes?

So I do need VT-x to do any 64 bit virtualization? Is this just a virtualbox limitation, or a general one?

Should I expect a big performance hit running a 32-bit GUEST under a 64-bit host? Ubuntu took over an hour to install on my powerful laptop, I've never seen it so slow.
pwaller
 
Posts: 5
Joined: 10. Mar 2009, 11:41

Re: 64 bit guest on 64 bit host (without VMX?)

Postby vbox4me2 » 10. Mar 2009, 13:36

You need vt-x for 64bit support, thats not specific to vbox, its how 64bit architecture works. There are some 64bit emulators.
32bit Guests run fine under a 64bit Host, ubuntu is just slow installing and starting, once running its ok though.
vbox4me2
Volunteer
 
Posts: 5222
Joined: 21. Nov 2008, 20:27
Location: Rotterdam


Return to Using VirtualBox

Who is online

Users browsing this forum: Google [Bot] and 4 guests