Messages in this thread | | | Date | Thu, 24 Mar 2011 20:06:10 +0200 | Subject | Re: [GIT PULL] SLAB changes for v2.6.39-rc1 | From | Pekka Enberg <> |
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On Thu, Mar 24, 2011 at 8:01 PM, Christoph Lameter <cl@linux.com> wrote: > On Thu, 24 Mar 2011, Pekka Enberg wrote: > >> On Thu, Mar 24, 2011 at 7:43 PM, Christoph Lameter <cl@linux.com> wrote: >> > The bug should only trigger on old AMD64 boxes that do not support >> > cmpxchg16b. >> >> Yup. Ingo is it possible to see /proc/cpuinfo of one of the affected >> boxes? I'll try your config but I'm pretty sure the problem doesn't >> trigger here. Like I said, I think the problem is that alternative >> instructions are not patched early enough for cmpxchg16b emulation to >> work for kmem_cache_init(). I tried my check_bugs() patch but it hangs >> during boot. I'll see if I can cook up a patch that does >> alternative_instructions() before kmem_cache_init() because I think >> those *should* be available during boot too. > > I forced the fallback to the _emu function to occur but could not trigger > the bug in kvm.
That's not the problem. I'm sure the fallback is just fine. What I'm saying is that the fallback is *not patched* to kernel text on Ingo's machines because alternative_instructions() happens late in the boot! So the problem is that on Ingo's boxes (that presumably have old AMD CPUs) we execute cmpxchg16b, not the fallback code.
Pekka
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