Re: [Xen-users] Advice on PCIe graphics card for Xen+X86_64 for X

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> I used a ScienticLinux 5.0 distro (mimics RedHat 5.0 but merged the
> Server and Enterprise versions) in a x86_64 arch. I ran into a problem,
> because while I can have X in the normal kernel, the Xen kernel, when I
> boot in dom0 is in text mode and can't load the Nvidia module. This is
> because Nvidia does not support Xen. There seems to be some patches for
> other distros (Suse, freeBSD) but I am afraid those might not work here
> ... anyway I want to avoid this.
>
> Also I was forced to install the OS in text mode, because the graphics
> card did not work out of the box with the distro. For what I want to do
> now, it is not essential to have a 3D graphics card. I want to have a
> dom0 for administration and to launch Linux as guests to create a
> virtual cluster (but where X should perform well in the guests).
>
> The machine's Motherboard is Intel S5000XVNSATA and I have  PCIe slots
> available. The question are:
> 1) Could someone please provide details about currently available
> graphic cards (PCIe) that work under Xen, kernel 2.1.18 (SL, RedHat) and
> x86_64 out of the box, so I could use X in both dom0 and domUs?

I'd have thought you could get your existing Nvidia card to work by using the 
open source "nv" driver that's included with Xorg.  It doesn't support the 
advanced features of the Nvidia cards, but it'll do 2D for you.  Maybe this 
is enough?  I used nv for a long time on various machines a few years ago and 
found it worked just fine for me (I wasn't using Xen on those machines at the 
time, though).

Regarding getting good X performance out of the guests themselves...  various 
people have played with passing through graphics devices directly to the 
guests so that they can have optimal graphics performance, but I don't know 
how much success has been had there.

Using the standard virtual framebuffers / VNC that Xen supports, don't expect 
to have brilliant guest graphics performance!  It's server-oriented, so the 
graphical interface will work OK for administration and for office-type 
tasks, but don't expect fast moving graphics / video to necessarily work 
well.

You could check out VMGL if you ever want to pass 3D operations from a guest 
to another VM / physical machine with decent performance though: 
http://www.cs.toronto.edu/~andreslc/xen-gl/

> 2) Is there a way that I could have both graphic cards installed so I
> could use the more powerful one when I boot with the normal kernel and
> the new one for Xen+X, when booting under the Xen kernel?

Well, I guess you probably could.  Easiest would be to hack your init scripts 
around a bit so that the X server got started with a different xorg.conf 
depending on what kernel you were booted into.

Actually, though, if you were going to do that you might as well just keep the 
Nvidia card there and hack your init scripts so that the xorg.conf either 
uses the binary "nvidia" driver or the open source "nv" driver.

Cheers,
Mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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