Re: MIPS: Add dependencies for HAVE_ARCH_TRANSPARENT_HUGEPAGE

[David Daney <ddaney.cavm@gmail.com>]

On 03/20/2013 03:33 PM, Sebastian Gottschall wrote:
> Am 04.03.2013 05:17, schrieb Ben Hutchings:
> > The MIPS implementation of transparent huge-pages (THP) is 64-bit only,
> > and of course also requires that the CPU supports huge-pages.
> >
> > Currently it's entirely possible to enable THP in other configurations,
> > which then fail to build due to pfn_pmd() not being defined.
> >
> > Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> > Cc: David Daney <david.daney@cavium.com>
> > ---
> > --- a/arch/mips/Kconfig
> > +++ b/arch/mips/Kconfig
> > @@ -19,7 +19,7 @@ config MIPS
> >       select HAVE_KRETPROBES
> >       select HAVE_DEBUG_KMEMLEAK
> >       select ARCH_BINFMT_ELF_RANDOMIZE_PIE
> > -    select HAVE_ARCH_TRANSPARENT_HUGEPAGE
> > +    select HAVE_ARCH_TRANSPARENT_HUGEPAGE if CPU_SUPPORTS_HUGEPAGES
> > && 64BIT
> >       select RTC_LIB if !MACH_LOONGSON
> >       select GENERIC_ATOMIC64 if !64BIT
> >       select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
> why? the mips32 74k platform (broadcom bcm4706 for instance) does
> support huge pages.
The hardware may support pages larger than 64K, but does the Linux 
kernel?  I think not.
> and some of these devices are also using highmem for
> accessing more than 128mb ram (which is totally broken in all current
> kernels too and causing filesystem corruptions)
> i was able to fix the highmem problem using a patch which was submitted
> but never taken into the mainline, but i just was able to get thb
> partially to work on mips32. but i think it would be possible to support
> this on mips32 as well. so why leaving it out?
As they say... Patches are welcome.  If you get Linux HUGE pages working 
for 32-bit kernels send a patch to enable the transparent variety as well.
David Daney