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On Wed, 18 May 2011 22:26:54 +0100, Orchid XP v8 wrote:
> On 18/05/2011 10:04 PM, Jim Henderson wrote:
>> On Wed, 18 May 2011 14:55:33 +0100, Invisible wrote:
>>
>>> For that matter, it should be fairly trivial to run QEMU inside QEMU
>>> inside QEMU, so...
>>
>> Actually, it isn't - virtualizing virtualization solutions doesn't tend
>> to work very well at all.
>
> QEMU doesn't use hardware virtualisation. It does software emulation
> only. This is why it's trivial to do what I described.
Even for software-based virtualization (emulation is different), it
wouldn't work so well, to the best of my knowledge.
> For stuff that uses real hardware virtualisation... yeah, that tends not
> to work. Although I have successfully run VirtualBox inside VMware
> Workstation. (Had to tweak some options though, turning off some of the
> hardware acceleration...)
It can be done, sure; it's not very stable. I've spent time working with
virtualization and doing something like trying to run XEN under VMware is
possible and sometimes works, but not reliably enough for what I needed
it for.
Jim
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On 18/05/2011 18:02, nemesis wrote:
> BTW, it should be useful for cloudy-like virtualization, running Linux
> apps directly from the browser... :)
Cloudy virtualisation. I like that... heh.
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>>> Actually, it isn't - virtualizing virtualization solutions doesn't tend
>>> to work very well at all.
>>
>> QEMU doesn't use hardware virtualisation. It does software emulation
>> only. This is why it's trivial to do what I described.
>
> Even for software-based virtualization (emulation is different), it
> wouldn't work so well, to the best of my knowledge.
My understanding is that QEMU does full software emulation of the guest
system. (It can even emulate an architecture different than the one it's
running on.) Assuming it emulates the full capabilities of the guest, I
don't see why you can't run QEMU inside QEMU.
If it's using the host hardware to accelerate things, then that of
course is a different matter. Generally the scheme only supports one
layer of virtualisation, not two.
>> For stuff that uses real hardware virtualisation... yeah, that tends not
>> to work. Although I have successfully run VirtualBox inside VMware
>> Workstation. (Had to tweak some options though, turning off some of the
>> hardware acceleration...)
>
> It can be done, sure; it's not very stable.
I'm sure it's not a very "supported" route, but I managed to get Windows
XP running inside Windows XP (running inside Windows XP). I only
actually wanted to see what VirtualBox is like, without installing it
for real. (Isn't that the point of desktop virtualisation? To test
things without "really" installing them?) I wouldn't recommend using
such a configuration "for real", no.
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On Thu, 19 May 2011 09:10:32 +0100, Invisible wrote:
>>>> Actually, it isn't - virtualizing virtualization solutions doesn't
>>>> tend to work very well at all.
>>>
>>> QEMU doesn't use hardware virtualisation. It does software emulation
>>> only. This is why it's trivial to do what I described.
>>
>> Even for software-based virtualization (emulation is different), it
>> wouldn't work so well, to the best of my knowledge.
>
> My understanding is that QEMU does full software emulation of the guest
> system. (It can even emulate an architecture different than the one it's
> running on.) Assuming it emulates the full capabilities of the guest, I
> don't see why you can't run QEMU inside QEMU.
It's not trival to emulate an emulation system under emulation. Just
like it isn't trivial to virtualize a virtualization system in a virtual
environment. Trust me, I've worked with this stuff quite a lot.
QEMU doesn't emulate the guest OS, just the hardware. That's the essence
of virtualization.
> If it's using the host hardware to accelerate things, then that of
> course is a different matter. Generally the scheme only supports one
> layer of virtualisation, not two.
That's not really what hardware virtualization does. It essentially
creates a separate Ring0 space within the hardware to run things at full
hardware speed.
>>> For stuff that uses real hardware virtualisation... yeah, that tends
>>> not to work. Although I have successfully run VirtualBox inside VMware
>>> Workstation. (Had to tweak some options though, turning off some of
>>> the hardware acceleration...)
>>
>> It can be done, sure; it's not very stable.
>
> I'm sure it's not a very "supported" route, but I managed to get Windows
> XP running inside Windows XP (running inside Windows XP). I only
> actually wanted to see what VirtualBox is like, without installing it
> for real. (Isn't that the point of desktop virtualisation? To test
> things without "really" installing them?) I wouldn't recommend using
> such a configuration "for real", no.
Yes, it's been *done*, but it's not particularly *stable*. For my own
purposes, I needed an environment that was stable enough to be reliable
for testing people's skills on virtualization technologies. Even the SMEs
that I talked to about it said "you're nuts because it just isn't stable
to do so".
Jim
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On 17/05/2011 11:22 PM, nemesis wrote:
> Fabrice Bellard, head of funky projects like FFmpeg and QEMU, wrote a
> 486 emulator in javascript and put a simplified Linux to run on it.
> Check it out, if you have latest version of Firefox or Chrome at least:
>
> http://bellard.org/jslinux
Note: This is still insane.
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