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SubjectRe: percpu crash on NetBurst
On 08/08/2011 12:55 PM, Tejun Heo wrote:
> Hello, Avi.
>
> On Sun, Aug 07, 2011 at 06:32:35PM +0300, Avi Kivity wrote:
> > qemu, under some conditions (-cpu host or -cpu kvm64), erroneously
> > passes family=15 as the virtual cpuid. This causes a BUG() in
> > percpu code during late boot:
> >
> > ------------[ cut here ]------------
> > kernel BUG at mm/percpu.c:577!
>

<snip>

> > All this applies to v3.0; current upstream (c2f340a69ca) fails even
> > worse, haven't yet determined exactly why.
> >
> > I'm surprised this hasn't been reported before; Ingo, don't you have
> > family=15 hosts in your test farm?
>
> Hmmm... I can't trigger the problem w/ kvm64 (I tried mounting and
> unmounting filesystems but it worked okay) and am quite skeptical this
> is a wide spread problem given that the percpu core code is used very
> widely and hasn't seen a lot of changes lately. Is there anything
> specific you need to do to trigger the condition? Can you try to
> print out the s_files addresses being allocated and freed?
>

Coming back to this, the trigger if cpuid family=6 and model>=13 (model
12 works). Looks like the code disables rep_good is some MSR doesn't
have the expected value. While we should configure the MSR correctly,
it looks like the fallback code for !rep_good is broken. Will look further.

--
error compiling committee.c: too many arguments to function



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