Subject: Re: [PATCH -V3 05/11] arch/powerpc: remove masking top 16 bit of va in tlb invalidate

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Mon, 23 Jul 2012 12:14:34 +0530

Paul Mackerras <[email-masked]> writes:

> On Mon, Jul 23, 2012 at 11:22:08AM +1000, Benjamin Herrenschmidt wrote:
>> On Mon, 2012-07-23 at 09:56 +1000, Paul Mackerras wrote:
>> > > That indicate we should not mask the top 16 bits. So remove the
>> > same.
>> > 
>> > Older versions of the architecture (2.02 and earler) require the
>> > masking, so we can't just unconditionally remove it, since that would
>> > potentially break POWER5 and PPC970.  People are definitely still
>> > running Linux bare-metal on PPC970s (though arguably not on POWER5). 
>> 
>> Are you sure ? I couldn't convince myself ... the old architectures say
>> that it only uses some of the bits but it doesn't mark the other ones as
>> "reserved" (as in must be 0).
>> 
>> (At least 1.x, I haven't looked at 2.x with x < 03)
>
> 2.01 and 2.02 say bits 0..15 must be zero.

is this 0..15 of va or 0..15 of AVA ?

if it is 0.. 15 then that clear bit is wrong right ? We are doing that
on a 64 bit va. So with that we already have ignored 0..14. 

-aneesh