Split Device Driver for video card?

Split Device Driver for video card?

[Teddy Song]

Hi, all.

I am trying to figure out how split device drivers work in Xen. However,
when I start a guest domain, I only see the following fields showing up in
Xenstore:

/local/domain/1/device/console/ .....
/local/domain/1/device/vbd/769/ .....

I didn't see other /local/domain/1/device fields. Does it mean not all device
drivers in Xen follow the split device driver model? (in other words, not all
device drivers in Xen have a frontend and a backend) If that's true, does video
card device driver follow the split device driver model?

Thanks in advance.


Best regards,
Teddy


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Re: Split Device Driver for video card?

[Daniel P. Berrange]

On Wed, Jan 09, 2008 at 10:37:12AM -0500, Teddy Song wrote:
> 
> Hi, all.
> 
> I am trying to figure out how split device drivers work in Xen. However,
> when I start a guest domain, I only see the following fields showing up in
> Xenstore:
> 
> /local/domain/1/device/console/ .....
> /local/domain/1/device/vbd/769/ .....
> 
> I didn't see other /local/domain/1/device fields. Does it mean not all device
> drivers in Xen follow the split device driver model? (in other words, not all
> device drivers in Xen have a frontend and a backend) If that's true, does video
> card device driver follow the split device driver model?

The console node you see  is actually the text mode console - this does
not follow XEn's usual mode for split device drivers. The video card does
follow the usual architecture - look for  'vfb' and 'vkbd' (keyboard/mouse)
backend nodes in /local/domain/0/backend/{vfb,vkbd} and frontend nods in
/local/domain/[guest id]/device/{vfb,vkbd}.  The only slightly unusual
thing about the video driver is that the backend is a 100% pure userspace
driver, whereas disk & network have their backends in kernel-space.

Dan.
-- 
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Re: Split Device Driver for video card?

[Mark Williamson]

Teddy, are you running an HVM domain?  If so, you won't see many device nodes 
in Xenstore since HVM domains don't use split device drivers for most things.

Cheers,
Mark

On Wednesday 09 January 2008, Daniel P. Berrange wrote:
> On Wed, Jan 09, 2008 at 10:37:12AM -0500, Teddy Song wrote:
> > Hi, all.
> >
> > I am trying to figure out how split device drivers work in Xen. However,
> > when I start a guest domain, I only see the following fields showing up
> > in Xenstore:
> >
> > /local/domain/1/device/console/ .....
> > /local/domain/1/device/vbd/769/ .....
> >
> > I didn't see other /local/domain/1/device fields. Does it mean not all
> > device drivers in Xen follow the split device driver model? (in other
> > words, not all device drivers in Xen have a frontend and a backend) If
> > that's true, does video card device driver follow the split device driver
> > model?
>
> The console node you see  is actually the text mode console - this does
> not follow XEn's usual mode for split device drivers. The video card does
> follow the usual architecture - look for  'vfb' and 'vkbd' (keyboard/mouse)
> backend nodes in /local/domain/0/backend/{vfb,vkbd} and frontend nods in
> /local/domain/[guest id]/device/{vfb,vkbd}.  The only slightly unusual
> thing about the video driver is that the backend is a 100% pure userspace
> driver, whereas disk & network have their backends in kernel-space.
>
> Dan.



-- 
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!

Split Device Driver for video card?

[Teddy Song]

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Hi, all.

I am trying to figure out how split device drivers work in Xen. However, 
when I start a guest domain, I only see the following fields showing up in 
Xenstore:

/local/domain/1/device/console/ .....
/local/domain/1/device/vbd/769/ .....

I didn't see other /local/domain/1/device fields. Does it mean not all device
drivers in Xen follow the split device driver model? (in other words, not all
device drivers in Xen have a frontend and a backend) If that's true, does video
card device driver follow the split device driver model?

Thanks in advance.


Best regards,
Teddy


_________________________________________________________________
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