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Re: [Xen-users] PV Drivers in Linux HVM DomU?

To: "Pasi Kärkkäinen" <pasik@xxxxxx>
Subject: Re: [Xen-users] PV Drivers in Linux HVM DomU?
From: "Emre Erenoglu" <erenoglu@xxxxxxxxx>
Date: Thu, 22 Nov 2007 15:57:23 +0100
Cc: Xen Users <xen-users@xxxxxxxxxxxxxxxxxxx>
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Hi Pasi, comments below:

On Nov 22, 2007 3:35 PM, Pasi Kärkkäinen <pasik@xxxxxx> wrote:
On Thu, Nov 22, 2007 at 01:47:06PM +0100, Emre Erenoglu wrote:
> Hi,
> Is it possible to use HVM (full virtualization) for Linux guests but use PV
> drivers instead inside the DomU for extra performance?



> What shall I do to be able to do it? Where can I download these drivers for
> several standard kernels? (HVM domU = standard distribution kernel,
> not-xen-aware)

You can download xen source tree and compile "unmodified drivers" from
there, or you can use the ones distributed with your distribution, if

OK, I will do that. I don't think my distribution has these drivers as a package.

> Or, does the recent introduction of VMI into the linux kernel make this
> automatic for us? i.e. if I use any recent kernel, such as Ubuntu's
> 2.6.22-14-generic, will paravirtualized disk/network drivers be
> automatically activated?

VMI is VMware's interface to run paravirtual Linux on VMware. It doesn't
work or help at all with Xen.

Well maybe I stated wrong, i was mentioning VMI (or whatever function it is) as a common way to enable standard kernels to work as Paravirtual when they detect the presence of a hypervisor. I think this is now standard for all, including VMWare and XEN.
FYI, it is possible to boot a 2.6.23 vanilla kernel as paravirtual DomU, but my question was if the paravirtual drivers were already there if I use HVM instead of Paravirtualization. I hope I mentioned it right...

If you're running paravirtual linux on xen, you already have paravirtualized
("full speed") drivers in use.

Yes,  however, my DomU crashes on boot with the PV kernel. I couldn't find why.

If you're using HVM domU on Xen, then you need to install Xen PV drivers on

-- Pasi

Thanks, just one last question, when I compile and modprobe these PV modules, how can I understand that they are actually working?   Do they print some message in dmesg?



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