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From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
To: Paul Mackerras <paulus@samba.org>
Subject: Re: [PATCH -V3 2/3] powerpc: Update kernel VSID range
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Date: Wed, 13 Mar 2013 19:14:02 +0530
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Paul Mackerras <paulus@samba.org> writes:

>>  BEGIN_FTR_SECTION
>>  	b	slb_finish_load
>>  END_MMU_FTR_SECTION_IFCLR(MMU_FTR_1T_SEGMENT)
>> @@ -91,24 +97,19 @@ _GLOBAL(slb_miss_kernel_load_vmemmap)
>>  	_GLOBAL(slb_miss_kernel_load_io)
>>  	li	r11,0
>>  6:
>> -	li	r9,0x1
>>  	/*
>> -	 * for 1T we shift 12 bits more.  slb_finish_load_1T will do
>> -	 * the necessary adjustment
>> +	 * context = (MAX_USER_CONTEXT) + ((ea >> 60) - 0xc) + 1
>>  	 */
>> -	rldimi  r10,r9,(CONTEXT_BITS + USER_ESID_BITS),0
>> +	rldicl	r9,r3,4,62
>> +	addis	r9,r9,8
>> +	subi	r9,r9,4
>
> If you did the context calculation earlier, before the "bne cr7,1f",
> you could save 3 more instructions.

We use r9 later as region id in 

#ifdef CONFIG_SPARSEMEM_VMEMMAP
	/* Check virtual memmap region. To be patches at kernel boot */
	cmpldi	cr0,r9,0xf
	bne	1f

hence i didn't do the above suggested change.

-aneesh