[Pkg-virtualbox-devel] 1.6.4

[Frank Mehnert]

Stefan,

On Tuesday 19 August 2008, Stefan Lippers-Hollmann wrote:
> Hi
>
> On Montag, 18. August 2008, Stefan Lippers-Hollmann wrote:
> > Hi
> >
> > On Sonntag, 17. August 2008, Stefan Lippers-Hollmann wrote:
> > > Hi
> > >
> > > On Sonntag, 17. August 2008, Michael Meskes wrote:
> > > > On Sun, Aug 17, 2008 at 04:16:52PM +0200, Stefan Lippers-Hollmann 
wrote:
> > > > > > boot failure usually already happens for me before the
> > > > > > framebuffer initializes, disabling the framebuffer (vga=0)
> > > > > > reveals vastly different panics which are also usually cut (don't
> > > > > > fit into 80*25 characters).
> >
> > [...]
> >
> > > For testing, I've now switched to grub2 (no graphics, simple grub.cfg),
> > > no changes, the most common error message is
> > > 	Decompressing Linux... Parsing ELF... done.
> > > 	Booting the kernel
> > > 	BUG: unable to handle kernel<1>BUG: unable to handle kernel<1>BUG:
> > > unable to h [another 20 lines like that]
> > > 	andle kernel<1>BUG: unable to handle kernel<1>BUG: unable to handle
> > > kernel NUL another one now ending in
> > > 	andle kernel<1>BUG: unable to handle kernel<1>BUG: unable to handle
> > > kernel pag ing request at 00001688
> > > The other traces which appear sometimes are just too badly cut at the
> > > top.
> > >
> > > What is strange though, is that there are no definitive results, while
> > > I wasn't able to boot 2.6.26-1-686 with virtualbox-ose 1.6.4 so far, it
> > > just now succeeded once, while a preemptive kernel continues to fail
> > > booting (at least with a much higher probability, even that one boots
> > > rarely).
> >
> > In the mean time I have bisected the issue back to
> >
> > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit
> >;h=e587cadd8f47e202a30712e2906a65a0606d5865
> >
> > Once that commit enters the kernel, it crashes as virtualbox-ose guest
> > for me. Given that this issue is hard to trigger reliably (it might just
> > boot properly 10 times in a row, but crash the whole day afterwards) and
> > because a 2.6.26.3-rc1 with that patch reverted is still compiling and
> > hasn't been tested yet, I'm not claiming that it actually is that commit
> > - yet.
>
> I've just finished building kernel 2.6.26.3-rc1 with commit
> e587cadd8f47e202a30712e2906a65a0606d5865 reverted and booting it into tty
> as a guest has succeeded in all tests so far, but the guest's X freezes
> shortly after logging into the desktop environment/ window manager (display
> manager and tty seem to be stable). So while the mentioned commit is
> definately closely related to the early boot crashes of 2.6.26 guests in
> virtualbox-ose, just reverting it isn't sufficient (this happens with both,
> 1.6.2-dfsg-1 and 1.6.4-1 (UNRELEASED, see the required change below) and
> their corresponding kernel modules, updated in lockstep for host and
> guest).
>
> > Likewise I'm not 100% positive if it's a kernel problem or a bug in
> > virtualbox-ose yet, but given that I'm not sure how much time I have
> > during the remaining week, I wanted to report the bisect results early.

Thanks for this investigation. To my understanding the changeset you found
is _definitely_ a problem. The problem is that the Linux kernel allows
to generate interrupts while some dangerous instructions are patched. This
is no problem on real hardware (interrupts are relatively seldom) but this
is a problem on virtual machines where this code executes much longer than
on real hardware.

If may understand the code wrong but I can't believe that they readded this
kind of bug. It was fixed in around 2.6.19.

See
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=e51959faa61278c762389802faf8ba1a40676628

Kind regards,

Frank
-- 
Dr.-Ing. Frank Mehnert    Sun Microsystems    http://www.sun.com/
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