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Subject: Re: [V2][PATCH] New MMU feature for new hpte format in ISA3
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
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Cc: linuxppc-dev@lists.ozlabs.org, Michael Ellerman <mpe@ellerman.id.au>,
 Paul Mackerras <paulus@samba.org>, Michael Neuling <mikey@neuling.org>
From: Balbir Singh <bsingharora@gmail.com>
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Date: Wed, 15 Jun 2016 17:19:00 +1000
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On 15/06/16 15:42, Aneesh Kumar K.V wrote:
> Balbir Singh <bsingharora@gmail.com> writes:
> 
>> On 15/06/16 10:38, Balbir Singh wrote:
>>>
>>> Thanks for a review, I'll do a V2 with some changes
>>>
>>> Balbir
>>>
>>
>> Michael, please review and check if you like the #ifdef,
>> since we are crossing the 32 bit boundary, I've used a
>> conditional define to select the feature.
> 
> 
> We really don't need to make it unsigned long. Take a look at
> 
> http://mid.gmane.org/1465395958-21349-9-git-send-email-aneesh.kumar@linux.vnet.ibm.com


The comment in the file states that


/*
 * First half is MMU families
 */

So effectively the first 16 bits are for families. Unless we decide to override
that decision. One can also debate the description of what a MMU family is :)


> 
> But I still am not sure why we need an mmu feature for selecting new hpte
> format. Why would the exiting ISA 3.0 check won't work?
> 

I thought I answered it in my previous email. The check for CPU_FTR_ARCH_300 is
too large and we don't want to use it unless advertised via ibm,pa-features.

> 
> For the pa-feature 58 byte look at
> http://mid.gmane.org/1465397003-26812-17-git-send-email-aneesh.kumar@linux.vnet.ibm.com