Kernel locks up after calling kernel_execve()

[Paul Mackerras]

Gerhard Pircher writes:

> Yeah, the northbridge hates the M bit! Thus the AmigaOne platform code

Wow.

> masks out the CPU_FTR_NEED_COHERENT flag and disables the L2 cache
> prefetch engines (I don't care about the performance loss).
> I couldn't find any other code that sets the M bit, except for huge TLB
> page support, but isn't that only for PPC64?

No it's not just for ppc64.  We had a patch that went in some time ago
to ensure that the M bit was set on various 32-bit platforms because
otherwise we got data corruption (due to a small cache in the
northbridge not being kept coherent with the processor cache).

Look for CPU_FTR_NEED_COHERENT in include/asm-powerpc/cputable.h and
arch/powerpc/mm/*.

Paul.