Re: IP27: CONFIG_TRANSPARENT_HUGEPAGE triggers bus errors

[Joshua Kinard <kumba@gentoo.org>]

On 11/10/2014 06:20, Thomas Bogendoerfer wrote:
> On Mon, Nov 10, 2014 at 11:51:06AM +0100, Ralf Baechle wrote:
>> Thomas,
>>
>> can you test CONFIG_TRANSPARENT_HUGEPAGE on an IP28?
>>
>> All in all the R10000's TLB is unproblematic; my gut feeling is that
>> rather something else specific to IP27 is spoiling the broth.
> 
> I'll give it a spin later today.
> 
> Thomas.

Try testing with and without CONFIG_HUGETLBFS in the kernel.  File systems ->
Pseudo filesystems -> HugeTLB file system support

So far, it seems adding that option in with CONFIG_TRANSPARENT_HUGEPAGE makes
both IP27 and IP30 behave.  Without, I get data bus errors or segfaults on IP27
running Gentoo's "emerge" program on PAGE_SIZE_4K.

IP30 seems to be fine on an R12000 with or without that option, but I only have
a dual R12K module to test against.  I've only had the R14K dual module for a
few days, and I could not reproduce the bus errors on that module, either.  So
I wonder if there is something funny with the hardware on the single R14K
module, which I did get IBE's on before.  And whether that will behave once
CONFIG_HUGETLBFS is in the kernel.

If so, maybe the fix is to make CONFIG_HUGETLBFS automatically selected if
CONFIG_TRANSPARENT_HUGEPAGE?

--J