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/*
 *  arch/ppc/kernel/hashtable.S
 *
 *  $Id: hashtable.S,v 1.1.1.1 2004-04-15 01:19:16 phoenix Exp $
 *
 *  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 <linux/config.h>
#include <asm/processor.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/cputable.h>
#include <asm/ppc_asm.h>
#include <kernel/ppc_defs.h>

#ifdef CONFIG_SMP
        .comm   hash_table_lock,4
#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.
 * r23 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, r2 - r7, ctr, lr.
 */
        .text
        .globl  hash_page
hash_page:
#ifdef CONFIG_PPC64BRIDGE
        mfmsr   r0
        clrldi  r0,r0,1         /* make sure it's in 32-bit mode */
        MTMSRD(r0)
        isync
#endif
        tophys(r7,0)                    /* gets -KERNELBASE into r7 */
#ifdef CONFIG_SMP
        addis   r2,r7,hash_table_lock@h
        ori     r2,r2,hash_table_lock@l
        mfspr   r5,SPRG3
        lwz     r0,PROCESSOR-THREAD(r5)
        oris    r0,r0,0x0fff
        b       10f
11:     lwz     r6,0(r2)
        cmpwi   0,r6,0
        bne     11b
10:     lwarx   r6,0,r2
        cmpwi   0,r6,0
        bne-    11b
        stwcx.  r0,0,r2
        bne-    10b
        isync
#endif
        /* Get PTE (linux-style) and check access */
        lis     r0,KERNELBASE@h         /* check if kernel address */
        cmplw   0,r4,r0
        mfspr   r2,SPRG3                /* current task's THREAD (phys) */
        ori     r3,r3,_PAGE_USER|_PAGE_PRESENT /* test low addresses as user */
        lwz     r5,PGDIR(r2)            /* 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,r23,32-12,29,29      /* 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     r5,0(r5)                /* get pmd entry */
        rlwinm. r5,r5,0,0,19            /* 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
        add     r2,r5,r7                /* convert to phys addr */
        rlwimi  r2,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,r2                 /* 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,r2                 /* attempt to update PTE */
        bne-    retry                   /* retry if someone got there first */

        mfsrin  r3,r4                   /* get segment reg for segment */
        mr      r2,r8                   /* we have saved r2 but not r8 */
        bl      create_hpte             /* add the hash table entry */
        mr      r8,r2

/*
 * htab_reloads counts the number of times we have to fault an
 * HPTE into the hash table.  This should only happen after a
 * fork (because fork does a flush_tlb_mm) or a vmalloc or ioremap.
 * Where a page is faulted into a process's address space,
 * update_mmu_cache gets called to put the HPTE into the hash table
 * and those are counted as preloads rather than reloads.
 */
        addis   r2,r7,htab_reloads@ha
        lwz     r3,htab_reloads@l(r2)
        addi    r3,r3,1
        stw     r3,htab_reloads@l(r2)

#ifdef CONFIG_SMP
        eieio
        addis   r2,r7,hash_table_lock@ha
        li      r0,0
        stw     r0,hash_table_lock@l(r2)
#endif

        /* Return from the exception */
        lwz     r3,_CCR(r21)
        lwz     r4,_LINK(r21)
        lwz     r5,_CTR(r21)
        mtcrf   0xff,r3
        mtlr    r4
        mtctr   r5
        lwz     r0,GPR0(r21)
        lwz     r1,GPR1(r21)
        lwz     r2,GPR2(r21)
        lwz     r3,GPR3(r21)
        lwz     r4,GPR4(r21)
        lwz     r5,GPR5(r21)
        lwz     r6,GPR6(r21)
        lwz     r7,GPR7(r21)
        /* we haven't used xer */
        mtspr   SRR1,r23
        mtspr   SRR0,r22
        lwz     r20,GPR20(r21)
        lwz     r22,GPR22(r21)
        lwz     r23,GPR23(r21)
        lwz     r21,GPR21(r21)
        RFI

#ifdef CONFIG_SMP
hash_page_out:
        eieio
        addis   r2,r7,hash_table_lock@ha
        li      r0,0
        stw     r0,hash_table_lock@l(r2)
        blr
#endif /* CONFIG_SMP */

/*
 * Add an entry for a particular page to the hash table.
 *
 * add_hash_page(unsigned context, unsigned long va, pte_t pte)
 *
 * 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 */

        /*
         * 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).  -- paulus
         */
        mfmsr   r10
        SYNC
        rlwinm  r0,r10,0,17,15          /* clear bit 16 (MSR_EE) */
        mtmsr   r0
        SYNC

#ifdef CONFIG_SMP
        lis     r9,hash_table_lock@h
        ori     r9,r9,hash_table_lock@l
        lwz     r8,PROCESSOR(r2)
        oris    r8,r8,10
10:     lwarx   r7,0,r9
        cmpi    0,r7,0
        bne-    11f
        stwcx.  r8,0,r9
        beq+    12f
11:     lwz     r7,0(r9)
        cmpi    0,r7,0
        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      r7,r5
1:      lwarx   r6,0,r7
        andi.   r0,r6,_PAGE_HASHPTE
        bne     9f                      /* if HASHPTE already set, done */
        ori     r5,r6,_PAGE_ACCESSED|_PAGE_HASHPTE
        stwcx.  r5,0,r7
        bne-    1b

        li      r7,0                    /* no address offset needed */
        bl      create_hpte

        lis     r8,htab_preloads@ha
        lwz     r3,htab_preloads@l(r8)
        addi    r3,r3,1
        stw     r3,htab_preloads@l(r8)

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

        lwz     r0,4(r1)
        mtlr    r0

        /* reenable interrupts */
        mtmsr   r10
        SYNC
        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 hash_table_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)

#ifndef CONFIG_PPC64BRIDGE
/* 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 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

#else
/* defines for the PTE format for 64-bit PPCs */
#define PTE_SIZE        16
#define PTEG_SIZE       128
#define LG_PTEG_SIZE    7
#define LDPTEu          ldu
#define STPTE           std
#define CMPPTE          cmpd
#define PTE_H           2
#define PTE_V           1
#define TST_V(r)        andi. r,r,PTE_V
#define SET_V(r)        ori r,r,PTE_V
#define CLR_V(r,t)      li t,PTE_V; andc r,r,t
#endif /* CONFIG_PPC64BRIDGE */

#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 */
#ifdef CONFIG_SMP
        ori     r8,r8,_PAGE_COHERENT    /* set M (coherence required) */
#endif

        /* Construct the high word of the PPC-style PTE (r5) */
#ifndef CONFIG_PPC64BRIDGE
        rlwinm  r5,r3,7,1,24            /* put VSID in 0x7fffff80 bits */
        rlwimi  r5,r4,10,26,31          /* put in API (abbrev page index) */
#else /* CONFIG_PPC64BRIDGE */
        clrlwi  r3,r3,8                 /* reduce vsid to 24 bits */
        sldi    r5,r3,12                /* shift vsid into position */
        rlwimi  r5,r4,16,20,24          /* put in API (abbrev page index) */
#endif /* CONFIG_PPC64BRIDGE */
        SET_V(r5)                       /* set V (valid) bit */

        /* Get the address of the primary PTE group in the hash table (r3) */
        .globl  hash_page_patch_A
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 */
        .globl  hash_page_patch_B
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 */
        .globl  hash_page_patch_C
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.
         */
        addis   r4,r7,next_slot@ha
        lwz     r6,next_slot@l(r4)
        addi    r6,r6,PTE_SIZE
        andi.   r6,r6,7*PTE_SIZE
#ifdef CONFIG_POWER4
        /*
         * Since we don't have BATs on POWER4, we rely on always having
         * PTEs in the hash table to map the hash table and the code
         * that manipulates it in virtual mode, namely flush_hash_page and
         * flush_hash_segments.  Otherwise we can get a DSI inside those
         * routines which leads to a deadlock on the hash_table_lock on
         * SMP machines.  We avoid this by never overwriting the first
         * PTE of each PTEG if it is already valid.
         *      -- paulus.
         */
        bne     102f
        li      r6,PTE_SIZE
102:
#endif /* CONFIG_POWER4 */
        stw     r6,next_slot@l(r4)
        add     r4,r3,r6

        /* update counter of evicted pages */
        addis   r6,r7,htab_evicts@ha
        lwz     r3,htab_evicts@l(r6)
        addi    r3,r3,1
        stw     r3,htab_evicts@l(r6)

#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

        .comm   next_slot,4
        .comm   primary_pteg_full,4
        .comm   htab_hash_searches,4

/*
 * Flush the entry for a particular page from the hash table.
 *
 * flush_hash_page(unsigned context, unsigned long va, pte_t *ptep)
 *
 * We assume that there is a hash table in use (Hash != 0).
 */
_GLOBAL(flush_hash_page)
        /* 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 code below trims to 24 bits */

        /*
         * We disable interrupts here, even on UP, because we want
         * the _PAGE_HASHPTE bit to be a reliable indication of
         * whether the HPTE exists.  -- paulus
         */
        mfmsr   r10
        rlwinm  r0,r10,0,17,15          /* clear bit 16 (MSR_EE) */
        SYNC
        mtmsr   r0
        SYNC

#ifdef CONFIG_SMP
        lis     r9,hash_table_lock@h
        ori     r9,r9,hash_table_lock@l
        lwz     r8,PROCESSOR(r2)
        oris    r8,r8,9
10:     lwarx   r7,0,r9
        cmpi    0,r7,0
        bne-    11f
        stwcx.  r8,0,r9
        beq+    12f
11:     lwz     r7,0(r9)
        cmpi    0,r7,0
        beq     10b
        b       11b
12:     isync
#endif

        /*
         * Check the _PAGE_HASHPTE bit in the linux PTE.  If it is
         * already clear, we're done.  If not, clear it (atomically)
         * and proceed.  -- paulus.
         */
1:      lwarx   r6,0,r5                 /* fetch the pte */
        andi.   r0,r6,_PAGE_HASHPTE
        beq     9f                      /* done if HASHPTE is already clear */
        rlwinm  r6,r6,0,31,29           /* clear HASHPTE bit */
        stwcx.  r6,0,r5                 /* update the pte */
        bne-    1b

        /* Construct the high word of the PPC-style PTE (r5) */
#ifndef CONFIG_PPC64BRIDGE
        rlwinm  r5,r3,7,1,24            /* put VSID in 0x7fffff80 bits */
        rlwimi  r5,r4,10,26,31          /* put in API (abbrev page index) */
#else /* CONFIG_PPC64BRIDGE */
        clrlwi  r3,r3,8                 /* reduce vsid to 24 bits */
        sldi    r5,r3,12                /* shift vsid into position */
        rlwimi  r5,r4,16,20,24          /* put in API (abbrev page index) */
#endif /* CONFIG_PPC64BRIDGE */
        SET_V(r5)                       /* set V (valid) bit */

        /* Get the address of the primary PTE group in the hash table (r3) */
        .globl  flush_hash_patch_A
flush_hash_patch_A:
        lis     r8,Hash_base@h          /* base address of hash table */
        rlwimi  r8,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,r8                /* make primary hash */
        li      r8,8                    /* PTEs/group */

        /* Search the primary PTEG for a PTE whose 1st (d)word matches r5 */
        mtctr   r8
        addi    r7,r3,-PTE_SIZE
1:      LDPTEu  r0,PTE_SIZE(r7)         /* get next PTE */
        CMPPTE  0,r0,r5
        bdnzf   2,1b                    /* loop while ctr != 0 && !cr0.eq */
        beq+    3f

        /* Search the secondary PTEG for a matching PTE */
        ori     r5,r5,PTE_H             /* set H (secondary hash) bit */
        .globl  flush_hash_patch_B
flush_hash_patch_B:
        xoris   r7,r3,Hash_msk>>16      /* compute secondary hash */
        xori    r7,r7,(-PTEG_SIZE & 0xffff)
        addi    r7,r7,-PTE_SIZE
        mtctr   r8
2:      LDPTEu  r0,PTE_SIZE(r7)
        CMPPTE  0,r0,r5
        bdnzf   2,2b
        bne-    4f                      /* should never fail to find it */

3:      li      r0,0
        STPTE   r0,0(r7)                /* invalidate entry */
4:      sync
        tlbie   r4                      /* in hw tlb too */
        sync

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

9:      mtmsr   r10
        SYNC
        blr