powerpc/64s/radix: Fix radix segment exception handling

[Michael Ellerman]

Nicholas Piggin <npiggin at gmail.com> writes:
> Michael Ellerman's on April 11, 2019 12:49 am:
>> On Fri, 2019-03-29 at 07:42:57 UTC, Nicholas Piggin wrote:
>>> Commit 48e7b76957 ("powerpc/64s/hash: Convert SLB miss handlers to C")
>>> broke the radix-mode segment exception handler. In radix mode, this is
>>> exception is not an SLB miss, rather it signals that the EA is outside
>>> the range translated by any page table.
>>> 
>>> The commit lost the radix feature alternate code patch, which can
>>> cause faults to some EAs to kernel BUG at arch/powerpc/mm/slb.c:639!
>>> 
>>> The original radix code would send faults to slb_miss_large_addr,
>>> which would end up faulting due to slb_addr_limit being 0. This patch
>>> sends radix directly to do_bad_slb_fault, which is a bit clearer.
>>> 
>>> Fixes: 48e7b76957 ("powerpc/64s/hash: Convert SLB miss handlers to C")
>>> Cc: Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com>
>>> Reported-by: Anton Blanchard <anton at samba.org>
>>> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
>>> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar at linux.ibm.com>
>> 
>> Applied to powerpc fixes, thanks.
>> 
>> https://git.kernel.org/powerpc/c/7100e8704b61247649c50551b965e71d
>
> I sent a v2 with a selftests that triggers the crash if you want it.
> Code was unchanged to no big deal there.

Yeah I checked the kernel part was unchanged so stuck with v1.

I also sent a self test, which is similar but slightly different to
yours, though yours is better in general. I'll try and merge them into
one test.

cheers