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From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
To: Paul Mackerras <paulus@ozlabs.org>, linuxppc-dev@ozlabs.org
Subject: Re: [PATCH 3/9] powerpc/mm/book3s-64: Use physical addresses in upper
 page table tree levels
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References: <1456108880-27464-1-git-send-email-paulus@ozlabs.org>
 <1456108880-27464-4-git-send-email-paulus@ozlabs.org>
Date: Mon, 22 Feb 2016 12:36:03 +0530
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Paul Mackerras <paulus@ozlabs.org> writes:

> From: Paul Mackerras <paulus@samba.org>
>
> This changes the Linux page tables to store physical addresses
> rather than kernel virtual addresses in the upper levels of the
> tree (pgd, pud and pmd) for 64-bit Book 3S machines.
>
> This frees up some high order bits, and will be needed with
> PowerISA v3.0 machines which read the page table tree in hardware
> in radix mode.
>

Radix mark the top two bits at upper level page table tree.

ie,


static inline void pud_populate(struct mm_struct *mm, pud_t *pud, pmd_t *pmd)
{
	pud_set(pud, __pgtable_ptr_val(pmd));
}

static inline void rpud_populate(struct mm_struct *mm, pud_t *pud, pmd_t *pmd)
{
	*pud = __pud(__pa(pmd) | RPUD_VAL_BITS);
}


I guess we will do the same with hash to keep them same ?

-aneesh