Re: [Xen-users] Uninitialized hardware under Xen Client?

[Andy Burns <lists.xensource.com@xxxxxxxxxxxxxx>]

On 06/07/2008 09:59, Kenneth Andresen wrote:

> I have been trying quite hard today to get the Xen working with some of
> my live cd's to test the PCI, but so far without any luck; 
It can be bit of a headache, while I have managed to get my TV tuner
card almost working, the domU has a tendency to panic with one set of
settings or the hardware doesn't function properly with another set of
settings (the swiotlb I was talking about)

> I am
> considering if my problems steam from having an Intel Quad Core rather
> than AMD, and trying to run it using HVM rather than para-virtual.
My machine is an intel quad core, so you're OK on that front, but if
your domU is HVM, then for PCI passthrough I believe you need to have
intel VT-d (as well as VT-i) support in hardware and xen. I gather this
should be supported by Q35/P45/X48 boards with chipsets and *might* be
supported by some boards with X38 chipsets.

Are you interested in windows domU as well as linux domU?

> I have tried to use the virt-manager to create an initial xen install,
virt-manager uses libvirt's XML config files, which don't have a way to
add pci passthrough, you need the xmdomain.cfg format files.

> name = "InsideSecurity"
> memory = 512
> root = "/dev/hdc ro"
> #root = "/dev/ram0 rw"
> kernel = "/root/isolinux/vmlinuz"
> #ramdisk = "/root/isolinux/miniroot.lz"
> vcpus = 1
> vif = [ 'mac=00:01:01:01:01:01' ]
> disk = [ "file:/boot/iso/INSERT-1.3.9b_en.iso,hdc,r" ]
> pci = ['07:03.0']
that's the right format

> However this fails with an the following error message:
>
> Error: (2, 'Invalid kernel', 'xc_dom_find_loader: no loader found\n')
I've only used xen "the other way" with pygrub as the bootloader, so
that the kernel is inside /dev/hdc and is extracted by the bootloader at
boot time, for xen to initialise the domU.

> While searching for information about my problems, I have come across
> that it is generally seen as better to use Para virtualization rather
> than hardware. Can para virtual work with unmodified linux client
> kernels or default pfSense (BSD based), or will I have to use HVM for this?
paravirt will probably get you better performance, but the domU kernel
has to know that it is running under xen (it can either be a specific
kernel built for xen, or a paravirt_ops kernel that can decide at boot
time whether it is on xen, or bare-metal)

with HVM the kernel believes it is running on bare-metal when it isn't
and xen/qemu provide the smoke and mirrors.

> Will HVM work as intended with Intel Quad Core cpu the default
> Redhat/Centos 5.2 kernel (kernel-xen-2.6.18-92.1.6.el5.x86_64) and Xen
> 3.0.4 with their respective patches, or will I need to use modified
> kernel / upgraded Xen version to 3.2?
you'll need the kernel-xen as the dom0, I'd be tempted to also use
kernel-xen for the domU (paravirt) but you can also use normal
kernel-2.6 for the domU (HVM) but I doubt you'll get PCI passthrough.

there is a third way, redhat recently release paravirt drivers for HVM
kernels, not tried them though and I don't think they're "in" centos yet.




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