Commit bf680d51 authored by Aneesh Kumar K.V's avatar Aneesh Kumar K.V Committed by Michael Ellerman
Browse files

powerpc/mm: Don't track subpage valid bit in pte_t 



This free up 11 bits in pte_t. In the later patch we also change
the pte_t format so that we can start supporting migration pte
at pmd level. We now track 4k subpage valid bit as below

If we have _PAGE_COMBO set, we override the _PAGE_F_GIX_SHIFT
and _PAGE_F_SECOND. Together we have 4 bits, each of them
used to indicate whether any of the 4 4k subpage in that group
is valid. ie,

[ group 1 bit ]   [ group 2 bit ]  ..... [ group 4 ]
[ subpage 1 - 4]  [ subpage 5- 8]  ..... [ subpage 13 - 16]

We still track each 4k subpage slot number and secondary hash
information in the second half of pgtable_t. Removing the subpage
tracking have some significant overhead on aim9 and ebizzy benchmark and
to support THP with 4K subpage, we do need a pgtable_t of 4096 bytes.

Signed-off-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 106713a1

arch/powerpc/include/asm/book3s/64/hash-4k.h

+1 −9
Original line number Diff line number Diff line
@@ -47,17 +47,9 @@ 
/* Bits to mask out from a PGD to get to the PUD page */

#define PGD_MASKED_BITS		0



/* PTE bits */

#define _PAGE_HASHPTE	0x0400 /* software: pte has an associated HPTE */

#define _PAGE_SECONDARY 0x8000 /* software: HPTE is in secondary group */

#define _PAGE_GROUP_IX  0x7000 /* software: HPTE index within group */

#define _PAGE_F_SECOND  _PAGE_SECONDARY

#define _PAGE_F_GIX     _PAGE_GROUP_IX

#define _PAGE_SPECIAL	0x10000 /* software: special page */



/* PTE flags to conserve for HPTE identification */

#define _PAGE_HPTEFLAGS (_PAGE_BUSY | _PAGE_HASHPTE | \

			 _PAGE_SECONDARY | _PAGE_GROUP_IX)

			 _PAGE_F_SECOND | _PAGE_F_GIX)



/* shift to put page number into pte */

#define PTE_RPN_SHIFT	(17)

arch/powerpc/include/asm/book3s/64/hash-64k.h

+7 −28
Original line number Diff line number Diff line
@@ -31,33 +31,13 @@ 
/* Bits to mask out from a PGD/PUD to get to the PMD page */

#define PUD_MASKED_BITS		0x1ff



/* Additional PTE bits (don't change without checking asm in hash_low.S) */

#define _PAGE_SPECIAL	0x00000400 /* software: special page */

#define _PAGE_HPTE_SUB	0x0ffff000 /* combo only: sub pages HPTE bits */

#define _PAGE_HPTE_SUB0	0x08000000 /* combo only: first sub page */

#define _PAGE_COMBO	0x10000000 /* this is a combo 4k page */

#define _PAGE_4K_PFN	0x20000000 /* PFN is for a single 4k page */



/* For 64K page, we don't have a separate _PAGE_HASHPTE bit. Instead,

 * we set that to be the whole sub-bits mask. The C code will only

 * test this, so a multi-bit mask will work. For combo pages, this

 * is equivalent as effectively, the old _PAGE_HASHPTE was an OR of

 * all the sub bits. For real 64k pages, we now have the assembly set

 * _PAGE_HPTE_SUB0 in addition to setting the HIDX bits which overlap

 * that mask. This is fine as long as the HIDX bits are never set on

 * a PTE that isn't hashed, which is the case today.

 *

 * A little nit is for the huge page C code, which does the hashing

 * in C, we need to provide which bit to use.

 */

#define _PAGE_HASHPTE	_PAGE_HPTE_SUB



/* Note the full page bits must be in the same location as for normal

 * 4k pages as the same assembly will be used to insert 64K pages

 * whether the kernel has CONFIG_PPC_64K_PAGES or not

#define _PAGE_COMBO	0x00020000 /* this is a combo 4k page */

#define _PAGE_4K_PFN	0x00040000 /* PFN is for a single 4k page */

/*

 * Used to track subpage group valid if _PAGE_COMBO is set

 * This overloads _PAGE_F_GIX and _PAGE_F_SECOND

 */

#define _PAGE_F_SECOND  0x00008000 /* full page: hidx bits */

#define _PAGE_F_GIX     0x00007000 /* full page: hidx bits */

#define _PAGE_COMBO_VALID	(_PAGE_F_GIX | _PAGE_F_SECOND)



/* PTE flags to conserve for HPTE identification */

#define _PAGE_HPTEFLAGS (_PAGE_BUSY | _PAGE_HASHPTE | _PAGE_COMBO)
@@ -103,8 +83,7 @@ static inline unsigned long __rpte_to_hidx(real_pte_t rpte, unsigned long index) 
}



#define __rpte_to_pte(r)	((r).pte)

#define __rpte_sub_valid(rpte, index) \

	(pte_val(rpte.pte) & (_PAGE_HPTE_SUB0 >> (index)))

extern bool __rpte_sub_valid(real_pte_t rpte, unsigned long index);

/*

 * Trick: we set __end to va + 64k, which happens works for

 * a 16M page as well as we want only one iteration

arch/powerpc/include/asm/book3s/64/hash.h

+5 −5
Original line number Diff line number Diff line
@@ -81,7 +81,12 @@ 
#define _PAGE_DIRTY		0x0080 /* C: page changed */

#define _PAGE_ACCESSED		0x0100 /* R: page referenced */

#define _PAGE_RW		0x0200 /* software: user write access allowed */

#define _PAGE_HASHPTE		0x0400 /* software: pte has an associated HPTE */

#define _PAGE_BUSY		0x0800 /* software: PTE & hash are busy */

#define _PAGE_F_GIX		0x7000 /* full page: hidx bits */

#define _PAGE_F_GIX_SHIFT	12

#define _PAGE_F_SECOND		0x8000 /* Whether to use secondary hash or not */

#define _PAGE_SPECIAL		0x10000 /* software: special page */



/* No separate kernel read-only */

#define _PAGE_KERNEL_RW		(_PAGE_RW | _PAGE_DIRTY) /* user access blocked by key */
@@ -210,11 +215,6 @@ 


#define PMD_BAD_BITS		(PTE_TABLE_SIZE-1)

#define PUD_BAD_BITS		(PMD_TABLE_SIZE-1)

/*

 * We save the slot number & secondary bit in the second half of the

 * PTE page. We use the 8 bytes per each pte entry.

 */

#define PTE_PAGE_HIDX_OFFSET (PTRS_PER_PTE * 8)



#ifndef __ASSEMBLY__

#define	pmd_bad(pmd)		(!is_kernel_addr(pmd_val(pmd)) \

arch/powerpc/mm/hash64_64k.c

+32 −2
Original line number Diff line number Diff line
@@ -15,6 +15,35 @@ 
#include <linux/mm.h>

#include <asm/machdep.h>

#include <asm/mmu.h>

/*

 * index from 0 - 15

 */

bool __rpte_sub_valid(real_pte_t rpte, unsigned long index)

{

	unsigned long g_idx;

	unsigned long ptev = pte_val(rpte.pte);



	g_idx = (ptev & _PAGE_COMBO_VALID) >> _PAGE_F_GIX_SHIFT;

	index = index >> 2;

	if (g_idx & (0x1 << index))

		return true;

	else

		return false;

}

/*

 * index from 0 - 15

 */

static unsigned long mark_subptegroup_valid(unsigned long ptev, unsigned long index)

{

	unsigned long g_idx;



	if (!(ptev & _PAGE_COMBO))

		return ptev;

	index = index >> 2;

	g_idx = 0x1 << index;



	return ptev | (g_idx << _PAGE_F_GIX_SHIFT);

}



int __hash_page_4K(unsigned long ea, unsigned long access, unsigned long vsid,

		   pte_t *ptep, unsigned long trap, unsigned long flags,
@@ -102,7 +131,7 @@ int __hash_page_4K(unsigned long ea, unsigned long access, unsigned long vsid, 
	 */

	if (!(old_pte & _PAGE_COMBO)) {

		flush_hash_page(vpn, rpte, MMU_PAGE_64K, ssize, flags);

		old_pte &= ~_PAGE_HPTE_SUB;

		old_pte &= ~_PAGE_HASHPTE | _PAGE_F_GIX | _PAGE_F_SECOND;

		goto htab_insert_hpte;

	}

	/*
@@ -192,7 +221,8 @@ repeat: 
	/* __real_pte use pte_val() any idea why ? FIXME!! */

	rpte.hidx &= ~(0xfUL << (subpg_index << 2));

	*hidxp = rpte.hidx  | (slot << (subpg_index << 2));

	new_pte |= (_PAGE_HPTE_SUB0 >> subpg_index);

	new_pte = mark_subptegroup_valid(new_pte, subpg_index);

	new_pte |=  _PAGE_HASHPTE;

	/*

	 * check __real_pte for details on matching smp_rmb()

	 */

arch/powerpc/mm/hash_low_64.S

+1 −5
Original line number Diff line number Diff line
@@ -285,7 +285,7 @@ htab_modify_pte: 


	/* Secondary group ? if yes, get a inverted hash value */

	mr	r5,r28

	andi.	r0,r31,_PAGE_SECONDARY

	andi.	r0,r31,_PAGE_F_SECOND

	beq	1f

	not	r5,r5

1:
@@ -473,11 +473,7 @@ ht64_insert_pte: 
	lis	r0,_PAGE_HPTEFLAGS@h

	ori	r0,r0,_PAGE_HPTEFLAGS@l

	andc	r30,r30,r0

#ifdef CONFIG_PPC_64K_PAGES

	oris	r30,r30,_PAGE_HPTE_SUB0@h

#else

	ori	r30,r30,_PAGE_HASHPTE

#endif

	/* Phyical address in r5 */

	rldicl	r5,r31,64-PTE_RPN_SHIFT,PTE_RPN_SHIFT

	sldi	r5,r5,PAGE_SHIFT

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