Subject: Re: [PATCH V2 10/11] powerpc/mm/radix: Make max pfn bits a variable

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Fri, 17 Mar 2017 14:24:08 +0530

Paul Mackerras <[email-masked]> writes:

> On Thu, Mar 16, 2017 at 04:02:08PM +0530, Aneesh Kumar K.V wrote:
>> This makes max pysical address bits a variable so that hash and radix
>> translation mode can choose what value to use. In this patch we also switch the
>> radix translation mode to use 57 bits. This make it resilient to future changes
>> to max pfn supported by platforms.
>> 
>> This patch is split from the previous one to make the review easier.
>> 
>> Signed-off-by: Aneesh Kumar K.V <[email-masked]>
>
> Why do we need to do this now?  It seems like this will add overhead
> every time we set a PTE for no current benefit.

I was trying to make sure that radix kernel can run on future version of
hardware where the max pfn bit is different.

-aneesh