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Re: [Xen-users] "'Invalid kernel', 'xc_dom_find_loader: no loader found\

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Subject: Re: [Xen-users] "'Invalid kernel', 'xc_dom_find_loader: no loader found\n" with new vanilla 2.6.23-rc8
From: Mark Williamson <mark.williamson@xxxxxxxxxxxx>
Date: Thu, 11 Oct 2007 04:31:22 +0100
Cc: Nico Prenzel <Nico.Prenzel@xxxxxxxx>
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> At my linux-source directory, I've found one big vmlinux (45 MB). But this
> file also gives me the same error message.

That's odd; if Xen support was built in correctly I'd expect that to work.

> If i do issue the following command, i do get the following (I've now
> switched to 2.6.23-rc9):
> debian:/home/linux-2.6.23-rc9# objdump -j __xen_guest -s ./vmlinux
> ./vmlinux:     file format elf32-i386

My vmlinux gives me back this too...

I think this is because the newer way of specifying XenLinux information is 
via elf notes.  The kernel.org merge omits legacy stuff.

If you do readelf -n ./vmlinux you ought to see some Linux stuff come back.

> >>What version of Xen are you running?
> I've installed the latest xen form testing. Until now: 3.1.1-rc3
> Xen-tools: 3.8

I'm running something ancient like 3.0.3.  I'm in the process of upgrading ;-)

> So, at this time I think the build process from vanilla kernel isn't doing
> the right thing.

I tried the build with the 2.6.23 release and successfully booted it on my 
system.  I didn't bother giving it any disks, just ran it long enough to see 
some console output...

Bear in mind that the mainline Linux implementation of Xen uses more / 
different common infrastructure and thus does things in different ways to the 
XenLinux the Xen project releases directly.  For instance, the console device 
used by mainline Linux to talk to the Xen console driver is hvc0 (a common 
hypervisor console device) rather than something Xen-specific.

So even once you've got a kernel that Xen will start, you'll need to 
pass "console=hvc0" on the command line if you want it to talk to you during 
boot ;-)  This confused me for a bit tonight until I figured it out!

Anyhow, the release of 2.6.23 should *definitely* give you a vmlinux that can 
boot.  Most of the size comes from symbols information, so if you strip the 
vmlinux it'll come down to a couple of megabytes first, anyhow.  I then 
gzipped mine and renamed it to vmlinuz, then successfully booted that 
(1.4Meg) kernel image under Xen - which worked fine too.  I'm not sure if 
there's a sanctioned way to get do the strip / gzip in the kernel build 
process, but doing it manually worked for me!

Maybe you could try again, possibly with the 2.6.23 release, and we could try 
and debug any problems you see there?


PS.  I've attached the vmlinuz I just built for reference.  This one is built 
to use PAE, so if you have a non-PAE Xen then it won't boot.

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!

Attachment: vmlinuz
Description: GNU Zip compressed data

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