Re: [Xen-devel] unstable tip not booting on x86-64 with 'domain_crash_sync'

[Ian Campbell <ian.campbell@xxxxxxxxxxxxx>]

Hi Muli,

On Sat, 2006-09-09 at 18:25 +0300, Muli Ben-Yehuda wrote:
> On Sat, Sep 09, 2006 at 10:58:40AM +0300, Muli Ben-Yehuda wrote:
> > On Thu, Sep 07, 2006 at 11:01:46PM +0300, Muli Ben-Yehuda wrote:
> > 
> > > > Binary chop on changeset revisions isn't a bad idea. I would think that 
> > > > such
> > > > a blatant failure mode couldn't have crept in all that long ago.
> > > 
> > > Yep, I'm working on it. Might take a while to narrow it down though,
> > > between me and the machine is a very slow VPN connection and a
> > > weekend... I'll keep you updated.
> > 
> > Ok, this changeset:
> > 
> > changeset:   11223:a4550b7488400c44a9f27c92115c8e364493837a
> > user:        Ian Campbell <ian.campbell@xxxxxxxxxxxxx>
> > date:        Tue Aug 22 14:20:43 2006 +0100
> > files:       linux-2.6-xen-sparse/arch/i386/kernel/vmlinux.lds.S
> > patches/linux-2.6.16.13/series
> > patches/linux-2.6.16.13/x86-put-note-sections-into-a-pt_note-segment-in-vmlinux.patch
> > patches/linux-2.6.16.13/x86_64-put-note-sections-into-a-pt_note-segment-in-vmlinux.patch
> > description:
> > [LINUX] Support creating ELF note segments in the kernel ELF image.
> > 
> > dies, while the previous one
> > (11222:cd4e7ace4e58d9e35c08ccaa4677c6b6d0cf137b) works.
> 
> Reverting the changes to x86-64's vmlinux.lds.S first introduced in
> this patch is enough to get my box booting again.
> - is this change necessary or can it be reverted for the time being?

It is necessary in order to have the ELF notes declared in head-xen.S
appear in the final image, we use them at boot time in place of the
older __xen_guest section. In theory we could remove the patch and rely
on the code falling back to __xen_guest, but I'd rather not.

I was told this independently yesterday, it is a problem with older (pre
2.16) binutils, I was able to reproduce it on Debian stable which has
2.15. It turns out that Jan Beulich posted a patch to xen-devel for the
problem a while back and it got forgotten about. I'm on a crappy
connection or I'd find a precise archive link for you -- It was on 28
August with message-id 44F3088B.76E4.0078.0@xxxxxxxxxx and subject
"update for
x86_64-put-note-sections-into-a-pt_note-segment-in-vmlinux.patch". It
basically moves the .bss declaration after all the .data ones.

I haven't committed this to Xen unstable because of
http://marc.theaimsgroup.com/?l=linux-kernel&m=115629369729911&w=2 (the
patch in question in this thread was from someone else, but it is the
same as Jan's). Andi Kleen has removed it from his queue for upstream
because of this report (I think).

Right now I think we should apply Jan's patch anyway, the above problem
looks a bit spurious and applying the patch would help us flush it out
anyway. I'll apply when I find a decent net connection (probably Monday
when I get to the office). If you could confirm the fix for me that
would be a very useful data point.

Thanks,
Ian.



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