Re: [Xen-users] New to Xen

["J. Roeleveld" <joost@xxxxxxxxxxxx>]

On Fri, November 11, 2011 12:56 pm, Niels Dettenbach wrote:
> Am Freitag, 11. November 2011, 12:36:43 schrieb J. Roeleveld:
>> My main issue with the documentation is that I have not been able to
>> find out which kernel-options are really needed for Xen
>
> This differs a bit between Dom0 and Domu and mainly between the "old"
> 2.6.38
> and the "new" (3.x - pvops) kernel. At least you have to enable all
> required
> XEN flags / drivers for backend or frontend.
>
> If it helps you i can post a example kernel config fpr 2.6.38 (SuSe
> backport -
> sys-kernel/xen-sources in portage) i used properly (but you have to add
> your
> hardware drivers by your own). On 3.2 i'm still fiddeling here... ;)

Always useful. The options you listed below should be sufficient.
I'd prefer to move to kernel 3.2 though. Will fiddle with the options when
the hardware and time is available.

> On 2.6.38 i use the same kernel for Dom0 and DomU for testing purposes
> (preferred to compile in most instead of building as modules).

I have seperate configs for the different domUs. (They don't all do the
same things and prefer to only enable what is really needed)

> The kernel does not build if i enable CONFIG_XEN_BLKDEV_TAP2

I read that somewhere as well.

> It could be wise to build the CONFIG_BLK_DEV_LOOP as module which allows
> you to change the number of loopback devices later / on running sys.

I tend to put that in the boot-options. But yes, it helps to have it later.

> --- snip ---
> # XEN
> CONFIG_XEN_PRIVILEGED_GUEST=y
> CONFIG_XEN_PRIVCMD=y
> CONFIG_XEN_DOMCTL=y
> CONFIG_XEN_XENBUS_DEV=y
> CONFIG_XEN_NETDEV_ACCEL_SFC_UTIL=m
> CONFIG_XEN_BACKEND=y
> CONFIG_XEN_BLKDEV_BACKEND=y
> CONFIG_XEN_BLKDEV_TAP=y

Is this one necessary when using LVM LVs for the partitions?
Eg. LVs names like domU_root, domU_swap,... ?

> # CONFIG_XEN_BLKDEV_TAP2 is not set
> CONFIG_XEN_NETDEV_BACKEND=y
> CONFIG_XEN_NETDEV_TX_SHIFT=8

Not seen this one yet (or missed it). Guess I've got some reading/googling
to do.

> # CONFIG_XEN_NETDEV_PIPELINED_TRANSMITTER is not set
> CONFIG_XEN_NETDEV_LOOPBACK=m
> CONFIG_XEN_PCIDEV_BACKEND=y
> CONFIG_XEN_PCIDEV_BACKEND_VPCI=y

Only when passing PCI-devices to domUs, right? :)

> # CONFIG_XEN_PCIDEV_BACKEND_PASS is not set
> # CONFIG_XEN_PCIDEV_BACKEND_SLOT is not set
> # CONFIG_XEN_PCIDEV_BE_DEBUG is not set
> CONFIG_XEN_TPMDEV_BACKEND=m
> CONFIG_XEN_SCSI_BACKEND=y
> CONFIG_XEN_USB_BACKEND=m

These three, only when passing the devices to the domU?

> CONFIG_XEN_BLKDEV_FRONTEND=y
> CONFIG_XEN_NETDEV_FRONTEND=y
> CONFIG_XEN_NETDEV_ACCEL_SFC_FRONTEND=m

Need to read up on this, name sounds interesting.

> CONFIG_XEN_SCSI_FRONTEND=y
> CONFIG_XEN_USB_FRONTEND=y
> # CONFIG_XEN_USB_FRONTEND_HCD_STATS is not set
> # CONFIG_XEN_USB_FRONTEND_HCD_PM is not set
> CONFIG_XEN_GRANT_DEV=y
> CONFIG_XEN_DISABLE_SERIAL=y
> CONFIG_XEN_SYSFS=y
> CONFIG_XEN_NR_GUEST_DEVICES=256
> CONFIG_XEN_COMPAT_030002_AND_LATER=y
> # CONFIG_XEN_COMPAT_030004_AND_LATER is not set
> # CONFIG_XEN_COMPAT_030100_AND_LATER is not set
> # CONFIG_XEN_COMPAT_030200_AND_LATER is not set
> # CONFIG_XEN_COMPAT_030300_AND_LATER is not set
> # CONFIG_XEN_COMPAT_030400_AND_LATER is not set
> # CONFIG_XEN_COMPAT_040000_AND_LATER is not set
> # CONFIG_XEN_COMPAT_040100_AND_LATER is not set
> # CONFIG_XEN_COMPAT_LATEST_ONLY is not set
> CONFIG_XEN_COMPAT=0x030002
> CONFIG_XEN_SMPBOOT=y
> CONFIG_XEN_DEVMEM=y
> CONFIG_XEN_BALLOON=y
> CONFIG_XEN_SCRUB_PAGES=y
> CONFIG_XEN_DEV_EVTCHN=y
> --- snap ---
>
>
> you may "split" that into two kernels as described in the official Gentoo
> Xen
> howto.
>
>
>> and how "xl" works as
>> it's not a true drop-in-replacement for "xm".
> This is true.
>
> I mainly used
>
>       xl help
>
> for general overview and
>
>       xl help <command>
>
> for a detailed description of each command here.
>
>> Is "xend" still needed?
> Yes (in Dom0).

Ok, the documentation I found was contradictory on this point.
What I found seemed to indicate that xl doesn't use xend and will work
without xend running.
But when using xm, xend is needed.

--
Joost


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