hash_low_32.S

/*
 *  PowerPC version
 *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
 *  Rewritten by Cort Dougan (cort@cs.nmt.edu) for PReP
 *    Copyright (C) 1996 Cort Dougan <cort@cs.nmt.edu>
 *  Adapted for Power Macintosh by Paul Mackerras.
 *  Low-level exception handlers and MMU support
 *  rewritten by Paul Mackerras.
 *    Copyright (C) 1996 Paul Mackerras.
 *
 *  This file contains low-level assembler routines for managing
 *  the PowerPC MMU hash table.  (PPC 8xx processors don't use a
 *  hash table, so this file is not used on them.)
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 *
 */

#include <asm/reg.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/cputable.h>
#include <asm/ppc_asm.h>
#include <asm/thread_info.h>
#include <asm/asm-offsets.h>

#ifdef CONFIG_SMP
	.section .bss
	.align	2
	.globl mmu_hash_lock
mmu_hash_lock:
	.space	4
#endif /* CONFIG_SMP */

/*
 * Sync CPUs with hash_page taking & releasing the hash
 * table lock
 */
#ifdef CONFIG_SMP
	.text
_GLOBAL(hash_page_sync)
	mfmsr   r10
	rlwinm  r0,r10,0,17,15          /* clear bit 16 (MSR_EE) */
	mtmsr   r0
	lis	r8,mmu_hash_lock@h
	ori	r8,r8,mmu_hash_lock@l
	lis	r0,0x0fff
	b	10f
11:	lwz	r6,0(r8)
	cmpwi	0,r6,0
	bne	11b
10:	lwarx	r6,0,r8
	cmpwi	0,r6,0
	bne-	11b
	stwcx.	r0,0,r8
	bne-	10b
	isync
	eieio
	li	r0,0
	stw	r0,0(r8)
	mtmsr	r10
	blr
#endif /* CONFIG_SMP */

/*
 * Load a PTE into the hash table, if possible.
 * The address is in r4, and r3 contains an access flag:
 * _PAGE_RW (0x400) if a write.
 * r9 contains the SRR1 value, from which we use the MSR_PR bit.
 * SPRG3 contains the physical address of the current task's thread.
 *
 * Returns to the caller if the access is illegal or there is no
 * mapping for the address.  Otherwise it places an appropriate PTE
 * in the hash table and returns from the exception.
 * Uses r0, r3 - r8, ctr, lr.
 */
	.text
_GLOBAL(hash_page)
	tophys(r7,0)			/* gets -KERNELBASE into r7 */
#ifdef CONFIG_SMP
	addis	r8,r7,mmu_hash_lock@h
	ori	r8,r8,mmu_hash_lock@l
	lis	r0,0x0fff
	b	10f
11:	lwz	r6,0(r8)
	cmpwi	0,r6,0
	bne	11b
10:	lwarx	r6,0,r8
	cmpwi	0,r6,0
	bne-	11b
	stwcx.	r0,0,r8
	bne-	10b
	isync
#endif
	/* Get PTE (linux-style) and check access */
	lis	r0,KERNELBASE@h		/* check if kernel address */
	cmplw	0,r4,r0
	mfspr	r8,SPRN_SPRG3		/* current task's THREAD (phys) */
	ori	r3,r3,_PAGE_USER|_PAGE_PRESENT /* test low addresses as user */
	lwz	r5,PGDIR(r8)		/* virt page-table root */
	blt+	112f			/* assume user more likely */
	lis	r5,swapper_pg_dir@ha	/* if kernel address, use */
	addi	r5,r5,swapper_pg_dir@l	/* kernel page table */
	rlwimi	r3,r9,32-12,29,29	/* MSR_PR -> _PAGE_USER */
112:	add	r5,r5,r7		/* convert to phys addr */
	rlwimi	r5,r4,12,20,29		/* insert top 10 bits of address */
	lwz	r8,0(r5)		/* get pmd entry */
	rlwinm.	r8,r8,0,0,19		/* extract address of pte page */
#ifdef CONFIG_SMP
	beq-	hash_page_out		/* return if no mapping */
#else
	/* XXX it seems like the 601 will give a machine fault on the
	   rfi if its alignment is wrong (bottom 4 bits of address are
	   8 or 0xc) and we have had a not-taken conditional branch
	   to the address following the rfi. */
	beqlr-
#endif
	rlwimi	r8,r4,22,20,29		/* insert next 10 bits of address */
	rlwinm	r0,r3,32-3,24,24	/* _PAGE_RW access -> _PAGE_DIRTY */
	ori	r0,r0,_PAGE_ACCESSED|_PAGE_HASHPTE

	/*
	 * Update the linux PTE atomically.  We do the lwarx up-front
	 * because almost always, there won't be a permission violation
	 * and there won't already be an HPTE, and thus we will have
	 * to update the PTE to set _PAGE_HASHPTE.  -- paulus.
	 */
retry:
	lwarx	r6,0,r8			/* get linux-style pte */
	andc.	r5,r3,r6		/* check access & ~permission */
#ifdef CONFIG_SMP
	bne-	hash_page_out		/* return if access not permitted */
#else
	bnelr-
#endif
	or	r5,r0,r6		/* set accessed/dirty bits */
	stwcx.	r5,0,r8			/* attempt to update PTE */
	bne-	retry			/* retry if someone got there first */

	mfsrin	r3,r4			/* get segment reg for segment */
	mfctr	r0
	stw	r0,_CTR(r11)
	bl	create_hpte		/* add the hash table entry */

#ifdef CONFIG_SMP
	eieio
	addis	r8,r7,mmu_hash_lock@ha
	li	r0,0
	stw	r0,mmu_hash_lock@l(r8)
#endif

	/* Return from the exception */
	lwz	r5,_CTR(r11)
	mtctr	r5
	lwz	r0,GPR0(r11)
	lwz	r7,GPR7(r11)
	lwz	r8,GPR8(r11)
	b	fast_exception_return

#ifdef CONFIG_SMP
hash_page_out:
	eieio
	addis	r8,r7,mmu_hash_lock@ha
	li	r0,0
	stw	r0,mmu_hash_lock@l(r8)
	blr
#endif /* CONFIG_SMP */

/*
 * Add an entry for a particular page to the hash table.
 *
 * add_hash_page(unsigned context, unsigned long va, unsigned long pmdval)
 *
 * We assume any necessary modifications to the pte (e.g. setting
 * the accessed bit) have already been done and that there is actually
 * a hash table in use (i.e. we're not on a 603).
 */
_GLOBAL(add_hash_page)
	mflr	r0
	stw	r0,4(r1)

	/* Convert context and va to VSID */
	mulli	r3,r3,897*16		/* multiply context by context skew */
	rlwinm	r0,r4,4,28,31		/* get ESID (top 4 bits of va) */
	mulli	r0,r0,0x111		/* multiply by ESID skew */
	add	r3,r3,r0		/* note create_hpte trims to 24 bits */

#ifdef CONFIG_SMP
	rlwinm	r8,r1,0,0,(31-THREAD_SHIFT) /* use cpu number to make tag */
	lwz	r8,TI_CPU(r8)		/* to go in mmu_hash_lock */
	oris	r8,r8,12
#endif /* CONFIG_SMP */

	/*
	 * We disable interrupts here, even on UP, because we don't
	 * want to race with hash_page, and because we want the
	 * _PAGE_HASHPTE bit to be a reliable indication of whether
	 * the HPTE exists (or at least whether one did once).
	 * We also turn off the MMU for data accesses so that we
	 * we can't take a hash table miss (assuming the code is
	 * covered by a BAT).  -- paulus
	 */
	mfmsr	r10
	SYNC
	rlwinm	r0,r10,0,17,15		/* clear bit 16 (MSR_EE) */
	rlwinm	r0,r0,0,28,26		/* clear MSR_DR */
	mtmsr	r0
	SYNC_601
	isync

	tophys(r7,0)

#ifdef CONFIG_SMP
	addis	r9,r7,mmu_hash_lock@ha
	addi	r9,r9,mmu_hash_lock@l
10:	lwarx	r0,0,r9			/* take the mmu_hash_lock */
	cmpi	0,r0,0
	bne-	11f
	stwcx.	r8,0,r9
	beq+	12f
11:	lwz	r0,0(r9)
	cmpi	0,r0,0
	beq	10b
	b	11b
12:	isync
#endif

	/*
	 * Fetch the linux pte and test and set _PAGE_HASHPTE atomically.
	 * If _PAGE_HASHPTE was already set, we don't replace the existing
	 * HPTE, so we just unlock and return.
	 */
	mr	r8,r5
	rlwimi	r8,r4,22,20,29
1:	lwarx	r6,0,r8
	andi.	r0,r6,_PAGE_HASHPTE
	bne	9f			/* if HASHPTE already set, done */
	ori	r5,r6,_PAGE_HASHPTE
	stwcx.	r5,0,r8
	bne-	1b

	bl	create_hpte

9:
#ifdef CONFIG_SMP
	eieio
	li	r0,0
	stw	r0,0(r9)		/* clear mmu_hash_lock */
#endif

	/* reenable interrupts and DR */
	mtmsr	r10
	SYNC_601
	isync

	lwz	r0,4(r1)
	mtlr	r0
	blr

/*
 * This routine adds a hardware PTE to the hash table.
 * It is designed to be called with the MMU either on or off.
 * r3 contains the VSID, r4 contains the virtual address,
 * r5 contains the linux PTE, r6 contains the old value of the
 * linux PTE (before setting _PAGE_HASHPTE) and r7 contains the
 * offset to be added to addresses (0 if the MMU is on,
 * -KERNELBASE if it is off).
 * On SMP, the caller should have the mmu_hash_lock held.
 * We assume that the caller has (or will) set the _PAGE_HASHPTE
 * bit in the linux PTE in memory.  The value passed in r6 should
 * be the old linux PTE value; if it doesn't have _PAGE_HASHPTE set
 * this routine will skip the search for an existing HPTE.
 * This procedure modifies r0, r3 - r6, r8, cr0.
 *  -- paulus.
 *
 * For speed, 4 of the instructions get patched once the size and
 * physical address of the hash table are known.  These definitions
 * of Hash_base and Hash_bits below are just an example.
 */
Hash_base = 0xc0180000
Hash_bits = 12				/* e.g. 256kB hash table */
Hash_msk = (((1 << Hash_bits) - 1) * 64)

/* defines for the PTE format for 32-bit PPCs */
#define PTE_SIZE	8
#define PTEG_SIZE	64
#define LG_PTEG_SIZE	6
#define LDPTEu		lwzu
#define LDPTE		lwz
#define STPTE		stw
#define CMPPTE		cmpw
#define PTE_H		0x40
#define PTE_V		0x80000000
#define TST_V(r)	rlwinm. r,r,0,0,0
#define SET_V(r)	oris r,r,PTE_V@h
#define CLR_V(r,t)	rlwinm r,r,0,1,31

#define HASH_LEFT	31-(LG_PTEG_SIZE+Hash_bits-1)
#define HASH_RIGHT	31-LG_PTEG_SIZE

_GLOBAL(create_hpte)
	/* Convert linux-style PTE (r5) to low word of PPC-style PTE (r8) */
	rlwinm	r8,r5,32-10,31,31	/* _PAGE_RW -> PP lsb */
	rlwinm	r0,r5,32-7,31,31	/* _PAGE_DIRTY -> PP lsb */
	and	r8,r8,r0		/* writable if _RW & _DIRTY */
	rlwimi	r5,r5,32-1,30,30	/* _PAGE_USER -> PP msb */
	rlwimi	r5,r5,32-2,31,31	/* _PAGE_USER -> PP lsb */
	ori	r8,r8,0xe14		/* clear out reserved bits and M */
	andc	r8,r5,r8		/* PP = user? (rw&dirty? 2: 3): 0 */
BEGIN_FTR_SECTION
	ori	r8,r8,_PAGE_COHERENT	/* set M (coherence required) */
END_FTR_SECTION_IFSET(CPU_FTR_NEED_COHERENT)

	/* Construct the high word of the PPC-style PTE (r5) */
	rlwinm	r5,r3,7,1,24		/* put VSID in 0x7fffff80 bits */
	rlwimi	r5,r4,10,26,31		/* put in API (abbrev page index) */
	SET_V(r5)			/* set V (valid) bit */

	/* Get the address of the primary PTE group in the hash table (r3) */
_GLOBAL(hash_page_patch_A)
	addis	r0,r7,Hash_base@h	/* base address of hash table */
	rlwimi	r0,r3,LG_PTEG_SIZE,HASH_LEFT,HASH_RIGHT    /* VSID -> hash */
	rlwinm	r3,r4,20+LG_PTEG_SIZE,HASH_LEFT,HASH_RIGHT /* PI -> hash */
	xor	r3,r3,r0		/* make primary hash */
	li	r0,8			/* PTEs/group */

	/*
	 * Test the _PAGE_HASHPTE bit in the old linux PTE, and skip the search
	 * if it is clear, meaning that the HPTE isn't there already...
	 */
	andi.	r6,r6,_PAGE_HASHPTE
	beq+	10f			/* no PTE: go look for an empty slot */
	tlbie	r4

	addis	r4,r7,htab_hash_searches@ha
	lwz	r6,htab_hash_searches@l(r4)
	addi	r6,r6,1			/* count how many searches we do */
	stw	r6,htab_hash_searches@l(r4)

	/* Search the primary PTEG for a PTE whose 1st (d)word matches r5 */
	mtctr	r0
	addi	r4,r3,-PTE_SIZE
1:	LDPTEu	r6,PTE_SIZE(r4)		/* get next PTE */
	CMPPTE	0,r6,r5
	bdnzf	2,1b			/* loop while ctr != 0 && !cr0.eq */
	beq+	found_slot

	/* Search the secondary PTEG for a matching PTE */
	ori	r5,r5,PTE_H		/* set H (secondary hash) bit */
_GLOBAL(hash_page_patch_B)
	xoris	r4,r3,Hash_msk>>16	/* compute secondary hash */
	xori	r4,r4,(-PTEG_SIZE & 0xffff)
	addi	r4,r4,-PTE_SIZE
	mtctr	r0
2:	LDPTEu	r6,PTE_SIZE(r4)
	CMPPTE	0,r6,r5
	bdnzf	2,2b
	beq+	found_slot
	xori	r5,r5,PTE_H		/* clear H bit again */

	/* Search the primary PTEG for an empty slot */
10:	mtctr	r0
	addi	r4,r3,-PTE_SIZE		/* search primary PTEG */
1:	LDPTEu	r6,PTE_SIZE(r4)		/* get next PTE */
	TST_V(r6)			/* test valid bit */
	bdnzf	2,1b			/* loop while ctr != 0 && !cr0.eq */
	beq+	found_empty

	/* update counter of times that the primary PTEG is full */
	addis	r4,r7,primary_pteg_full@ha
	lwz	r6,primary_pteg_full@l(r4)
	addi	r6,r6,1
	stw	r6,primary_pteg_full@l(r4)

	/* Search the secondary PTEG for an empty slot */
	ori	r5,r5,PTE_H		/* set H (secondary hash) bit */
_GLOBAL(hash_page_patch_C)
	xoris	r4,r3,Hash_msk>>16	/* compute secondary hash */
	xori	r4,r4,(-PTEG_SIZE & 0xffff)
	addi	r4,r4,-PTE_SIZE
	mtctr	r0
2:	LDPTEu	r6,PTE_SIZE(r4)
	TST_V(r6)
	bdnzf	2,2b
	beq+	found_empty
	xori	r5,r5,PTE_H		/* clear H bit again */

	/*
	 * Choose an arbitrary slot in the primary PTEG to overwrite.
	 * Since both the primary and secondary PTEGs are full, and we
	 * have no information that the PTEs in the primary PTEG are
	 * more important or useful than those in the secondary PTEG,
	 * and we know there is a definite (although small) speed
	 * advantage to putting the PTE in the primary PTEG, we always
	 * put the PTE in the primary PTEG.
	 *
	 * In addition, we skip any slot that is mapping kernel text in
	 * order to avoid a deadlock when not using BAT mappings if
	 * trying to hash in the kernel hash code itself after it has
	 * already taken the hash table lock. This works in conjunction
	 * with pre-faulting of the kernel text.
	 *
	 * If the hash table bucket is full of kernel text entries, we'll
	 * lockup here but that shouldn't happen
	 */

1:	addis	r4,r7,next_slot@ha		/* get next evict slot */
	lwz	r6,next_slot@l(r4)
	addi	r6,r6,PTE_SIZE			/* search for candidate */
	andi.	r6,r6,7*PTE_SIZE
	stw	r6,next_slot@l(r4)
	add	r4,r3,r6
	LDPTE	r0,PTE_SIZE/2(r4)		/* get PTE second word */
	clrrwi	r0,r0,12
	lis	r6,etext@h
	ori	r6,r6,etext@l			/* get etext */
	tophys(r6,r6)
	cmpl	cr0,r0,r6			/* compare and try again */
	blt	1b

#ifndef CONFIG_SMP
	/* Store PTE in PTEG */
found_empty:
	STPTE	r5,0(r4)
found_slot:
	STPTE	r8,PTE_SIZE/2(r4)

#else /* CONFIG_SMP */
/*
 * Between the tlbie above and updating the hash table entry below,
 * another CPU could read the hash table entry and put it in its TLB.
 * There are 3 cases:
 * 1. using an empty slot
 * 2. updating an earlier entry to change permissions (i.e. enable write)
 * 3. taking over the PTE for an unrelated address
 *
 * In each case it doesn't really matter if the other CPUs have the old
 * PTE in their TLB.  So we don't need to bother with another tlbie here,
 * which is convenient as we've overwritten the register that had the
 * address. :-)  The tlbie above is mainly to make sure that this CPU comes
 * and gets the new PTE from the hash table.
 *
 * We do however have to make sure that the PTE is never in an invalid
 * state with the V bit set.
 */
found_empty:
found_slot:
	CLR_V(r5,r0)		/* clear V (valid) bit in PTE */
	STPTE	r5,0(r4)
	sync
	TLBSYNC
	STPTE	r8,PTE_SIZE/2(r4) /* put in correct RPN, WIMG, PP bits */
	sync
	SET_V(r5)
	STPTE	r5,0(r4)	/* finally set V bit in PTE */
#endif /* CONFIG_SMP */

	sync		/* make sure pte updates get to memory */
	blr

	.section .bss
	.align	2
next_slot:
	.space	4
primary_pteg_full:
	.space	4
htab_hash_searches:
	.space	4
	.previous

/*
 * Flush the entry for a particular page from the hash table.
 *
 * flush_hash_pages(unsigned context, unsigned long va, unsigned long pmdval,
 *		    int count)
 *
 * We assume that there is a hash table in use (Hash != 0).
 */
_GLOBAL(flush_hash_pages)
	tophys(r7,0)

	/*
	 * We disable interrupts here, even on UP, because we want
	 * the _PAGE_HASHPTE bit to be a reliable indication of
	 * whether the HPTE exists (or at least whether one did once).
	 * We also turn off the MMU for data accesses so that we
	 * we can't take a hash table miss (assuming the code is
	 * covered by a BAT).  -- paulus
	 */
	mfmsr	r10
	SYNC
	rlwinm	r0,r10,0,17,15		/* clear bit 16 (MSR_EE) */
	rlwinm	r0,r0,0,28,26		/* clear MSR_DR */
	mtmsr	r0
	SYNC_601
	isync

	/* First find a PTE in the range that has _PAGE_HASHPTE set */
	rlwimi	r5,r4,22,20,29
1:	lwz	r0,0(r5)
	cmpwi	cr1,r6,1
	andi.	r0,r0,_PAGE_HASHPTE
	bne	2f
	ble	cr1,19f
	addi	r4,r4,0x1000
	addi	r5,r5,4
	addi	r6,r6,-1
	b	1b

	/* Convert context and va to VSID */
2:	mulli	r3,r3,897*16		/* multiply context by context skew */
	rlwinm	r0,r4,4,28,31		/* get ESID (top 4 bits of va) */
	mulli	r0,r0,0x111		/* multiply by ESID skew */
	add	r3,r3,r0		/* note code below trims to 24 bits */

	/* Construct the high word of the PPC-style PTE (r11) */
	rlwinm	r11,r3,7,1,24		/* put VSID in 0x7fffff80 bits */
	rlwimi	r11,r4,10,26,31		/* put in API (abbrev page index) */
	SET_V(r11)			/* set V (valid) bit */

#ifdef CONFIG_SMP
	addis	r9,r7,mmu_hash_lock@ha
	addi	r9,r9,mmu_hash_lock@l
	rlwinm	r8,r1,0,0,(31-THREAD_SHIFT)
	add	r8,r8,r7
	lwz	r8,TI_CPU(r8)
	oris	r8,r8,9
10:	lwarx	r0,0,r9
	cmpi	0,r0,0
	bne-	11f
	stwcx.	r8,0,r9
	beq+	12f
11:	lwz	r0,0(r9)
	cmpi	0,r0,0
	beq	10b
	b	11b
12:	isync
#endif

	/*
	 * Check the _PAGE_HASHPTE bit in the linux PTE.  If it is
	 * already clear, we're done (for this pte).  If not,
	 * clear it (atomically) and proceed.  -- paulus.
	 */
33:	lwarx	r8,0,r5			/* fetch the pte */
	andi.	r0,r8,_PAGE_HASHPTE
	beq	8f			/* done if HASHPTE is already clear */
	rlwinm	r8,r8,0,31,29		/* clear HASHPTE bit */
	stwcx.	r8,0,r5			/* update the pte */
	bne-	33b

	/* Get the address of the primary PTE group in the hash table (r3) */
_GLOBAL(flush_hash_patch_A)
	addis	r8,r7,Hash_base@h	/* base address of hash table */
	rlwimi	r8,r3,LG_PTEG_SIZE,HASH_LEFT,HASH_RIGHT    /* VSID -> hash */
	rlwinm	r0,r4,20+LG_PTEG_SIZE,HASH_LEFT,HASH_RIGHT /* PI -> hash */
	xor	r8,r0,r8		/* make primary hash */

	/* Search the primary PTEG for a PTE whose 1st (d)word matches r5 */
	li	r0,8			/* PTEs/group */
	mtctr	r0
	addi	r12,r8,-PTE_SIZE
1:	LDPTEu	r0,PTE_SIZE(r12)	/* get next PTE */
	CMPPTE	0,r0,r11
	bdnzf	2,1b			/* loop while ctr != 0 && !cr0.eq */
	beq+	3f

	/* Search the secondary PTEG for a matching PTE */
	ori	r11,r11,PTE_H		/* set H (secondary hash) bit */
	li	r0,8			/* PTEs/group */
_GLOBAL(flush_hash_patch_B)
	xoris	r12,r8,Hash_msk>>16	/* compute secondary hash */
	xori	r12,r12,(-PTEG_SIZE & 0xffff)
	addi	r12,r12,-PTE_SIZE
	mtctr	r0
2:	LDPTEu	r0,PTE_SIZE(r12)
	CMPPTE	0,r0,r11
	bdnzf	2,2b
	xori	r11,r11,PTE_H		/* clear H again */
	bne-	4f			/* should rarely fail to find it */

3:	li	r0,0
	STPTE	r0,0(r12)		/* invalidate entry */
4:	sync
	tlbie	r4			/* in hw tlb too */
	sync

8:	ble	cr1,9f			/* if all ptes checked */
81:	addi	r6,r6,-1
	addi	r5,r5,4			/* advance to next pte */
	addi	r4,r4,0x1000
	lwz	r0,0(r5)		/* check next pte */
	cmpwi	cr1,r6,1
	andi.	r0,r0,_PAGE_HASHPTE
	bne	33b
	bgt	cr1,81b

9:
#ifdef CONFIG_SMP
	TLBSYNC
	li	r0,0
	stw	r0,0(r9)		/* clear mmu_hash_lock */
#endif

19:	mtmsr	r10
	SYNC_601
	isync
	blr