[PATCH V2] powerpc/mm: Don't do debug print before we do feature fixup

[Denis Kirjanov]

On 6/19/16, Benjamin Herrenschmidt <benh at kernel.crashing.org> wrote:
> On Sat, 2016-06-18 at 23:57 +0530, Aneesh Kumar K.V wrote:
>> We use feature fixup in segment and page fault path and hence we should
>> not call any function that can cause either of these before we finish
>> feature fixup.
>>
>> Calling into early debug routine can result in segment fault as updated
>> in
>> https://lkml.kernel.org/r/CAOJe8K2L8D1M_yZPmyiZ11JvJ+HAS0aFHOnsqaY=xLOnQTA3AA@mail.gmail.com
>>
>> Avoid the segment fault by removing the debug print. Also remove the
>> matching closing debug print at the end of the function.
>
> Please add a comment at the beginning of setup_system() explaining
> the situation. IE, that until the fixups are done, not even debug
> printfs can be used.
>
Right, otherwise we'll hit the same issue in the future.

> It used to work though, the fact that we used 256M segment in that
> case wasn't an issue, in part because btext only really existed on
> machines that didn't have 1T segments. It was only ever going to be
> a segment fault, the rest was bolted (early ioremap).
>
> Ben.
>
>