Re: [Qemu-ppc] [Qemu-devel] [PATCH] target-ppc: Init dcache and icache size for e500 user mode

[Meador Inge]

On 04/13/2012 06:40 AM, Andreas Färber wrote:

> Am 12.04.2012 19:24, schrieb Scott Wood:
>> On 04/12/2012 11:59 AM, Andreas Färber wrote:
>>> Am 10.04.2012 22:04, schrieb Meador Inge:
>>>> commit f7aa558396dd0f6b7a2b22c05cb503c655854102 pulled the dcache and 
>>>> icache
>>>> line size initialization inside of a '#if !defined(CONFIG_USER_ONLY)' 
>>>> block.
>>>> This is not correct because instructions like 'dcbz' need the dcache size
>>>> initialized even for user mode.
>>>>
>>>> Signed-off-by: Meador Inge <address@hidden>
>>>
>>> Looks okay and compiles,
>>>
>>> Reviewed-by: Andreas Färber <address@hidden>
>>>
>>> Scott, are you planning to review this e500 patch? Or should I go ahead
>>> and apply?
>>
>> I'm OK with it, though it may make more sense for USER_ONLY to just pick
>> an arbitrary cache line size (probably 32) than to try to imitate a
>> specific core.
> 
> Meador, what was your specific problem: The value being zero or not
> matching real hardware?

My specific problem was the value being zero.  Therefore nothing actually got
cleared because the 'dcbz' implementation uses 'dcache_line_size' as an upper
bound on a loop.

On a side note, the way I actually ran into this was by running a application
linked against an optimized version of glibc for e500 that uses 'dcbz' in
'memset'.  ld.so wasn't correctly clearing .bss as a result.  That was fun to
debug :-)

> Scott's suggestion would avoid some #ifdef'ery so I'd prefer that if
> possible. I'm planning for a PULL later today, so let me know.

Sounds good to me.  I think the #ifdef stuff is gross, but I wasn't sure of way
around it.

-- 
Meador Inge
CodeSourcery / Mentor Embedded
http://www.mentor.com/embedded-software