Andrew Morton wrote on Friday, March 24, 2006 6:54 PM
> "Chen, Kenneth W" <[email protected]> wrote:
> >
> > Mark Rustad wrote on Friday, March 24, 2006 9:52 AM
> > > I have narrowed this down to DEBUG_PAGEALLOC. If that option is
> > > enabled, attempts to reference areas mmap-ed from hugetlbfs files
> > > fault forever. You can see that I had that set in the failing config
> > > I reported below.
> >
> > Yeah, it turns out that the debug option is not compatible with hugetlb
> > page support. That debug option turns off PSE. Once it is turned off in
> > CR4, cpu will ignore pse bit in the pmd and causing infinite page-not-
> > present fault :-(
>
> I wonder if any of the other architectures which implement both these
> features might have problems too.
Only 32-bit x86 arch implements both. We get away by not having DEBUG_PAGEALLOC
feature on any other arch.
I read the ia32 processor manual, it says the pse flag in CR4 controls
4K/4M mapping in addition to pse bit in page directory entry. But in
PAE mode, cr4.pse is ignored and pse bit in pmd controls 4K/2M mapping.
I was going to verify that on my ia32 box, but apparently, turning on
64G highmem gives me machine reset at boot. (is it a known regression?)
X86-64 surly ignores cr4.pse for 4K/2M mapping. It is solely controlled
by pse bit in pmd.
- Ken
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