Re: [PATCH 2/5] powerpc/head fsl: move the temp 4KiB mapping to TLB0

[Sebastian Andrzej Siewior <sebastian@breakpoint.cc>]

* Kumar Gala | 2010-02-17 21:09:08 [-0600]:

>
>On Jan 15, 2010, at 10:41 AM, Sebastian Andrzej Siewior wrote:
>
>> From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
>> 
>> Right now the setup code takes ESEL of the current mapping and puts the
>> temporary into ESEL (old_ESEL & 1 ) + 1 which is either one or two.
>> This is actually not required since all slots in TLB0 are invalid by now
>> and can be used.
>> This patch moved the temp mapping to TLB0, ESEL[0]. The invalidation of
>> TLB0 does not care about IPPROT so that part can go as well.
>> The benefit is that now the setup code may set every slot of TLB1 while
>> before that it was not allowed to touch ESEL one or two depending on the
>> old_ESEL.
>> 
>> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
>> ---
>> arch/powerpc/kernel/head_fsl_booke.S |   20 +++++---------------
>> 1 files changed, 5 insertions(+), 15 deletions(-)
>
>this is problematic, we can't assume that TLB0 is safe.  It possible some other software is running on a second core and does a broadcast tlbivax which will wipe what's in TLB0.

Ah right SMP. So if CPU0 would wait until CPU1-X are up and kick them
one by one could make it work but is not that pretty.
So let me think of something. I will probably just skip the current
mapping while making new ones for kexec.

>- k

Sebastian