Re: [Xen-users] 2.6.18.8 xen.org dom0 kernel w/RHEL 5 PV on HVM guests

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Thu, Mar 18, 2010 at 12:46:11PM -0700, Andrew Evans wrote:
> I've been beating my head against the wall trying to get stub domains
> working with PV on HVM guests running RHEL 5. Up to now I've been using
> the RHEL 5 dom0 kernel, but that doesn't work with stub domains because
> gntdev isn't built in (and can't be built as a module either -- I
> tried). So I built the 2.6.18.8 dom0 kernel from xen-unstable.hg. That
> got stub domains working with RHEL 5 HVM guests, but PV on HVM guests
> fail to find the root filesystem when initrd gets ready to pivot to the
> real root filesystem. PV on HVM without stub domain has the same problem.
> 
> --- begin domU console output ---
> Creating block device nodes.
> Loading xen-platform-pci.ko module
> GSI 16 sharing vector 0xA9 and IRQ 16
> ACPI: PCI Interrupt 0000:00:03.0[A] -> GSI 28 (level, low) -> IRQ 169
> Xen version 3.4.
> Hypercall area is 1 pages.
> Grant table initialized
> Loading xen-vbd.ko module
> Loading xen-balloon.ko module
> xen_mem: Initialising balloon driver.
> Loading xen-vnif.ko module
> netfront: Initialising virtual ethernet driver.
> Loading jbd.ko module
> netfront: device eth0 has copying receive path.
> Loading ext3.ko module
> Loading xen-vbd.ko module
> insmod: error inserting '/lib/xen-vbd.ko': -1 File exists
> Loading xen-vbd.ko module
> insmod: error inserting '/lib/xen-vbd.ko': -1 File exists
> Trying to resume from /dev/xvda2
> Unable to access resume device (/dev/xvda2)


Unable to access... hmm.


> Creating root device.
> Registering block device major 202
>  xvda:Mounting root filesystem.
>  xvda1 xvda2 xvda3
> mount: could not find filesystem '/dev/root'

I guess it's the same problem here..


> Setting up other filesystems.
> Setting up new root fs
> setuproot: moving /dev failed: No such file or directory
> no fstab.sys, mounting internal defaults
> setuproot: error mounting /proc: No such file or directory
> setuproot: error mounting /sys: No such file or directory
> Switching to new root and running init.
> unmounting old /dev
> unmounting old /proc
> unmounting old /sys
> switchroot: mount failed: No such file or directory
> Kernel panic - not syncing: Attempted to kill init!
> --- end domU console output ---
> 
> Notice that the PV disks and their partitions are detected.
>

Yeah, but they don't work for some reason..
 
> Kernel command line is root=LABEL=ROOT, but root=/dev/xvda3 doesn't work
> either.
> 
> This same VM boots fine if I reboot the hypervisor with the RHEL 5 dom0
> kernel.
> 
> /var/log/xen/* show nothing out of the ordinary. The only hint of a
> problem are these lines from xm dmesg:
> 
> (XEN) event_channel.c:192:d0 EVTCHNOP failure: domain 13, error -22
> (XEN) event_channel.c:192:d0 EVTCHNOP failure: domain 13, error -22
> (XEN) event_channel.c:192:d0 EVTCHNOP failure: domain 13, error -22
> 

These sound related..

> If I boot this same VM without disabling the IDE drivers, it mounts
> filesystems using /dev/hd* and starts up successfully. Now here's the
> baffling part: I can then mount / and /home using /dev/xvd*! So the
> paravirt disk driver *is* working once the domU boots off /dev/hd*, but
> for some reason it doesn't work when I try to boot from /dev/xvd* directly.
> 
> So my questions are:
> 
> 1. Why can't the initrd mount /dev/xvd* to / ?
> 

Because the devices don't work for some reason..

> 2. Why does this work with the RHEL 5 dom0 kernel but not with a
> similarly-configured xen-unstable 2.6.18.8 dom0 kernel?
> 

That's a good question.

> xen-unstable 2.6.18.8 dom0 kernel config attached. I've gotten the
> Xen-related stuff as close to RHEL 5 as I can, but available CONFIG_*
> defines vary somewhat between the two kernel source trees.
> 
> Thanks for any help anyone can provide.
> 

So the dom0 kernel was the only thing you changed? 
You used the same Xen hypervisor for both dom0 kernels? which hypervisor 
version? 

-- Pasi


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