
QEMU 2.0.0 Released - sciurus
http://article.gmane.org/gmane.comp.emulators.qemu/267615
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doktrin
QEMU looks interesting. I have a few questions about its intended use case.

1\. My understanding is that the primary use case of QEMU is for server
virtualization on Linux hosts leveraging KVM. Is there a use-case for QEMU on
non-Linux hosts?

2\. I have read that QEMU excels in server virtualization but lags behind
VirtualBox in desktop virtualization. Is this still the case? [1]

3\. Is it considered "slow" for cross-architecture virtualization? [1]

[1] [http://superuser.com/questions/447293/does-qemus-
performance...](http://superuser.com/questions/447293/does-qemus-performance-
still-lag-virtualboxs-and-is-there-a-way-to-improve-i)

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pm215
Whether you think it's "slow" for cross-architecture use depends on your
standards. It's always going to be slower than using the native CPU, because
we have to emulate everything, and even with a JIT that's not going to be
fast. Empirically not much effort is being put into trying to make the
emulation/JIT faster (and there are serious technical obstacles as well as
mere lack of effort/time), but if your target being emulated is a 200MHz
embedded dev board then we can probably manage to go as fast as that in
software... In any case the QEMU target is often more convenient for debugging
or simply more easily available than the real hardware.

~~~
moyix
It is sometimes a bit disheartening to see so much development effort go
toward the virtualization/KVM/Xen side rather than seeing improvements in TCG.
I realize that Redhat (and maybe others?) funds a lot of development in that
area, so it's natural that that's where most of the improvements are. I mostly
use QEMU as a CPU emulator, though, and it's frustrating to see so little
activity on the TCG side, especially when it comes to things like bugfixes
(Win7 x64 bluescreens under TCG, mipsel loadvm broken, to name two issues that
have bitten me).

Still, kudos to the developers for making some things better (TCG actually
does seem noticeably faster in 2.0.0) and congratulations on the 2.0.0
release!

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dorfsmay
TCG?

~~~
ris
"Tiny Code Generator", the JIT for cross architecture emulation.

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threeio
Completely read this as QEMM and flashed back to DOS days. :)

~~~
micro-ram
[http://en.wikipedia.org/wiki/DESQview](http://en.wikipedia.org/wiki/DESQview)

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awda
Anyone know if there are good tools for migrating a VMware .vmx and
accompanying files to a QEMU machine? Or is this more complicated than I
imagine? I'd like to ditch the VMware crap modules that break with every
kernel upgrade in favor of KVM.

~~~
karlmdavis
I did just that when I switched my server from ESXi (which used the same
formats). For me, the vmware2libvirt command from Ubuntu's virt-goodies
package did the trick.

I documented my transition in some of the sections on this page:
[https://justdavis.com/karl/it/davis/servers/eddings/vms.html](https://justdavis.com/karl/it/davis/servers/eddings/vms.html)

~~~
awda
Thanks, this was very helpful. Here's what I did (converting VMware
Workstation VM):

    
    
      1) Followed rwmj's guide to setting up a br0 device for libvirt in Fedora.
      2) Deleted all vmware snapshots. sync. sync.
      3) Grabbed vmware2libvirt from Ubuntu (it's just a standalone python script) and
         used it with --bridge br0 -f foo.vmx > foo.xml.
      4) Converted my vmdk to raw with qemu-img, moved it to /var/lib/libvirtd per your
         instructions
      5) Edited my xml to point to the right disk, use the qemu/raw driver, use the right
         path for kvm (/urs/bin/qemu-kvm on Fedora).
      6) Import into libvirt with virsh define foo.xml
      7) virsh start foo
    

It just works! Great. And virt-viewer over qemu+ssh is great; I run this VM on
a headless box on the LAN from my desktop.

~~~
JoeAltmaier
Helpful, thanks. But I'm reminded of my brother's email about how simple it
was to create a Linux kernel for a tv-controller - 3 pages of build
instructions, ending with "So easy!" What is it about Linux folks ...

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djschnei
Why would you use QEMU over virtualbox? (Serious question)

~~~
chjj
The VirtualBox virtualization drivers have serious issues. They're written so
poorly that they're notorious for causing kernel panics on linux. The kernel
devs consider your kernel tainted if you load the virtualbox modules.

I've crashed so hard using virtualbox that I didn't even _get_ a kernel panic,
just a box that wouldn't even respond to alt+sysrq.

On top of this, I personally prefer QEMU because it doesn't come with a clunky
GUI.

~~~
octopus
To be fair, VirtualBox runs flawlessly on OSX and Windows. I've also used
VirtualBox without problems on Ubuntu. What Linux distribution you use ?

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gtaylor
I've had Ubuntu 12.04 guests crash hard (like the commenter mentioned) on OSX
and Linux hosts with VirtualBox.

~~~
octopus
Probably has something to do with the 3D acceleration Unity needs.

In my case (MacBook Air 2013 with 8GB of RAM I run Ubuntu 12.04.4 without a
problem).

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gtaylor
My installs are headless, no 3D accel or Unity needed.

As originally mentioned, the VBox kernel modules are of poor quality. You may
or may not trigger an edge case in your daily use, with or without a desktop
environment.

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ausjke
This is simply awesome. Congratulations!

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bjz_
What is QEMU and why do I care? It would be helpful if that had been in the
first paragraph. I am going to dig deeper, but I'm sure a huge number of
people didn't.

~~~
Zikes
I know where you're coming from, and I've had the same reaction to a few other
similar posts on HN, however before I posted that reaction I realized two
things:

1\. If it's on the front page of HN then a lot of other folks around here
probably know what it is already.

2\. If it got voted up fairly quickly, it's probably also a big or important
technology that I should familiarize myself with, at least superficially.

~~~
bjz_
Thanks for that perspective, that's a good way of looking at it. It's easy to
get overly dismissive and lazy and it's good to have a reality check.

