[PATCH] powerpc: rework 4xx PTE access and TLB miss

[Josh Boyer]

On Tue, 01 Jul 2008 14:35:42 +1000
Benjamin Herrenschmidt <benh at kernel.crashing.org> wrote:

> This is some preliminary work to improve TLB management on SW loaded
> TLB powerpc platforms. This introduce support for non-atomic PTE
> operations in pgtable-ppc32.h and removes write back to the PTE from
> the TLB miss handlers. In addition, the DSI interrupt code no longer
> tries to fixup write permission, this is left to generic code, and
> _PAGE_HWWRITE is gone.

I tried testing this on a Sequoia board this morning.  Kernel boots,
but then it hangs when starting the init process.  The last message
seen is:

INIT: version 2.86
booting                                                      

The setup is an tftp'd kernel via U-Boot using cuImage, nfsroot
filesystem.  Sequoia has an FPU, and CONFIG_PPC_FPU is set.

I reverted this patch and used the latest powerpc-next branch and it
boots fine.

Seems something is wrong here still.  I suspect the DSI handler
changes, but I have no proof and haven't debugged it yet.  Until we
get it fixed, I don't feel overly comfortable putting it in the next
branch.  Which board and setup did you test with?

josh