Re: [Xen-users] New to Xen: safety concerns (Linux Dom0, Windows DomU)

["Fajar A. Nugraha" <list@xxxxxxxxx>]

On Fri, Sep 9, 2011 at 11:05 AM, Chris Angelico <rosuav@xxxxxxxxx> wrote:
> On Fri, Sep 9, 2011 at 1:41 PM, Drake Wilson <drake@xxxxxxxxxxxxxx> wrote:
>> One of your problems here is that VGA passthrough (at least if you want
>> it to hit the domU's BIOS) can actually be very hit-or-miss, though it's
>> gotten much better over time:
>>
>>  http://wiki.xensource.com/xenwiki/XenVGAPassthrough
>
> Thanks, an excellent document.
>
> "Xen VGA graphics passthru is a special form of PCI passthru, and PCI
> passthru dedicates the PCI device (graphics card) to exactly one
> single VM."
>
> I assume I can switch it to a different VM on the fly? That is, boot
> with the graphics card dedicated to dom0 Linux, then fire up domU
> Windows and hand control over.

Nope.

AFAIK the PCI device has to be hidden from dom0 to make it assignable
to domU, and once dom0 uses it (e.g. for console output) there is no
way to hide it.

>
>> Can you describe which trouble you're worried about in particular, if any?
>
> Googling for 'xen uninstall' shows up a variety of people asking
> similar questions:
> http://forums.opensuse.org/english/get-technical-help-here/applications/418253-how-uninstall-xen.html
> - seems to have uninstalled cleanly
> http://www.linuxformat.com/forums/viewtopic.php?t=377 - not too clear
> on the question itself there
> http://ubuntuforums.org/archive/index.php/t-953793.html - required
> some manual cleanup and not sure if it really cleaned up (dated 2008)
> http://www.firewall.cx/ftopict-6304.html - no resolution, no responses
> at all (dated 2009)
>
> Not enough weight of evidence to turn me away from Xen, but enough to
> be concerned about.

It ... depends.

Generally speaking, if you're expecting automated install/uninstall
which JUST WORKS, I wouldn't recommend you to use xen. Too many things
involved that might require manual intervention, like:
- bridged networking. The recommended method now is to create bridges manually
- grub config. Entries for native and xen boot is different, and
(depending on your kernel version) might require different kernel

> I want to play graphical Windows games. It's a 64-bit system with 8GB
> of RAM and a fairly new nVidia chipset video card (don't remember the
> spec atm), so in theory I should be able to give 2-3GB to a 32-bit
> WinXP and let that run happily, while leaving 5-6GB of real RAM for
> everything else.

I'd actually recommend you do something like
- use windows as native OS
- install virtualbox
- setup guests as needed
- use firewall on windows side to block all traffic TO windows, but
allow everything to guests

Simpler, easier to maintain.

-- 
Fajar

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