root/arch/powerpc/mm/nohash/tlb_low_64e.S
/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 *  Low level TLB miss handlers for Book3E
 *
 *  Copyright (C) 2008-2009
 *      Ben. Herrenschmidt (benh@kernel.crashing.org), IBM Corp.
 */

#include <linux/pgtable.h>
#include <asm/processor.h>
#include <asm/reg.h>
#include <asm/page.h>
#include <asm/mmu.h>
#include <asm/ppc_asm.h>
#include <asm/asm-offsets.h>
#include <asm/cputable.h>
#include <asm/exception-64e.h>
#include <asm/ppc-opcode.h>
#include <asm/kvm_asm.h>
#include <asm/kvm_booke_hv_asm.h>
#include <asm/feature-fixups.h>

#define VPTE_PMD_SHIFT  (PTE_INDEX_SIZE)
#define VPTE_PUD_SHIFT  (VPTE_PMD_SHIFT + PMD_INDEX_SIZE)
#define VPTE_PGD_SHIFT  (VPTE_PUD_SHIFT + PUD_INDEX_SIZE)
#define VPTE_INDEX_SIZE (VPTE_PGD_SHIFT + PGD_INDEX_SIZE)

/**********************************************************************
 *                                                                    *
 * TLB miss handling for Book3E with a bolted linear mapping          *
 * No virtual page table, no nested TLB misses                        *
 *                                                                    *
 **********************************************************************/

/*
 * Note that, unlike non-bolted handlers, TLB_EXFRAME is not
 * modified by the TLB miss handlers themselves, since the TLB miss
 * handler code will not itself cause a recursive TLB miss.
 *
 * TLB_EXFRAME will be modified when crit/mc/debug exceptions are
 * entered/exited.
 */
.macro tlb_prolog_bolted intnum addr
        mtspr   SPRN_SPRG_GEN_SCRATCH,r12
        mfspr   r12,SPRN_SPRG_TLB_EXFRAME
        std     r13,EX_TLB_R13(r12)
        std     r10,EX_TLB_R10(r12)
        mfspr   r13,SPRN_SPRG_PACA

        mfcr    r10
        std     r11,EX_TLB_R11(r12)
#ifdef CONFIG_KVM_BOOKE_HV
BEGIN_FTR_SECTION
        mfspr   r11, SPRN_SRR1
END_FTR_SECTION_IFSET(CPU_FTR_EMB_HV)
#endif
        DO_KVM  \intnum, SPRN_SRR1
        std     r16,EX_TLB_R16(r12)
        mfspr   r16,\addr               /* get faulting address */
        std     r14,EX_TLB_R14(r12)
        ld      r14,PACAPGD(r13)
        std     r15,EX_TLB_R15(r12)
        std     r10,EX_TLB_CR(r12)
START_BTB_FLUSH_SECTION
        mfspr r11, SPRN_SRR1
        andi. r10,r11,MSR_PR
        beq 1f
        BTB_FLUSH(r10)
1:
END_BTB_FLUSH_SECTION
        std     r7,EX_TLB_R7(r12)
.endm

.macro tlb_epilog_bolted
        ld      r14,EX_TLB_CR(r12)
        ld      r7,EX_TLB_R7(r12)
        ld      r10,EX_TLB_R10(r12)
        ld      r11,EX_TLB_R11(r12)
        ld      r13,EX_TLB_R13(r12)
        mtcr    r14
        ld      r14,EX_TLB_R14(r12)
        ld      r15,EX_TLB_R15(r12)
        ld      r16,EX_TLB_R16(r12)
        mfspr   r12,SPRN_SPRG_GEN_SCRATCH
.endm

/* Data TLB miss */
        START_EXCEPTION(data_tlb_miss_bolted)
        tlb_prolog_bolted BOOKE_INTERRUPT_DTLB_MISS SPRN_DEAR

        /* We need _PAGE_PRESENT and  _PAGE_ACCESSED set */

        /* We do the user/kernel test for the PID here along with the RW test
         */
        /* We pre-test some combination of permissions to avoid double
         * faults:
         *
         * We move the ESR:ST bit into the position of _PAGE_BAP_SW in the PTE
         * ESR_ST   is 0x00800000
         * _PAGE_BAP_SW is 0x00000010
         * So the shift is >> 19. This tests for supervisor writeability.
         * If the page happens to be supervisor writeable and not user
         * writeable, we will take a new fault later, but that should be
         * a rare enough case.
         *
         * We also move ESR_ST in _PAGE_DIRTY position
         * _PAGE_DIRTY is 0x00001000 so the shift is >> 11
         *
         * MAS1 is preset for all we need except for TID that needs to
         * be cleared for kernel translations
         */

        mfspr   r11,SPRN_ESR

        srdi    r15,r16,60              /* get region */
        rldicl. r10,r16,64-PGTABLE_EADDR_SIZE,PGTABLE_EADDR_SIZE+4
        bne-    dtlb_miss_fault_bolted  /* Bail if fault addr is invalid */

        rlwinm  r10,r11,32-19,27,27
        rlwimi  r10,r11,32-16,19,19
        cmpwi   r15,0                   /* user vs kernel check */
        ori     r10,r10,_PAGE_PRESENT
        oris    r11,r10,_PAGE_ACCESSED@h

        bne     tlb_miss_kernel_bolted

tlb_miss_user_bolted:
#ifdef CONFIG_PPC_KUAP
        mfspr   r10,SPRN_MAS1
        rlwinm. r10,r10,0,0x3fff0000
        beq-    tlb_miss_fault_bolted /* KUAP fault */
#endif

tlb_miss_common_bolted:
/*
 * This is the guts of the TLB miss handler for bolted-linear.
 * We are entered with:
 *
 * r16 = faulting address
 * r15 = crap (free to use)
 * r14 = page table base
 * r13 = PACA
 * r11 = PTE permission mask
 * r10 = crap (free to use)
 */
        rldicl  r15,r16,64-PGDIR_SHIFT+3,64-PGD_INDEX_SIZE-3
        cmpldi  cr0,r14,0
        clrrdi  r15,r15,3
        beq     tlb_miss_fault_bolted   /* No PGDIR, bail */

        ldx     r14,r14,r15             /* grab pgd entry */

        rldicl  r15,r16,64-PUD_SHIFT+3,64-PUD_INDEX_SIZE-3
        clrrdi  r15,r15,3
        cmpdi   cr0,r14,0
        bge     tlb_miss_fault_bolted   /* Bad pgd entry or hugepage; bail */
        ldx     r14,r14,r15             /* grab pud entry */

        rldicl  r15,r16,64-PMD_SHIFT+3,64-PMD_INDEX_SIZE-3
        clrrdi  r15,r15,3
        cmpdi   cr0,r14,0
        bge     tlb_miss_fault_bolted
        ldx     r14,r14,r15             /* Grab pmd entry */

        rldicl  r15,r16,64-PAGE_SHIFT+3,64-PTE_INDEX_SIZE-3
        clrrdi  r15,r15,3
        cmpdi   cr0,r14,0
        bge     tlb_miss_fault_bolted
        ldx     r14,r14,r15             /* Grab PTE, normal (!huge) page */

        /* Check if required permissions are met */
        andc.   r15,r11,r14
        rldicr  r15,r14,64-(PTE_RPN_SHIFT-PAGE_SHIFT),63-PAGE_SHIFT
        bne-    tlb_miss_fault_bolted

        /* Now we build the MAS:
         *
         * MAS 0   :    Fully setup with defaults in MAS4 and TLBnCFG
         * MAS 1   :    Almost fully setup
         *               - PID already updated by caller if necessary
         *               - TSIZE need change if !base page size, not
         *                 yet implemented for now
         * MAS 2   :    Defaults not useful, need to be redone
         * MAS 3+7 :    Needs to be done
         */
        clrrdi  r11,r16,12              /* Clear low crap in EA */
        clrldi  r15,r15,12              /* Clear crap at the top */
        rlwimi  r11,r14,32-19,27,31     /* Insert WIMGE */
        rlwimi  r15,r14,32-8,22,25      /* Move in U bits */
        mtspr   SPRN_MAS2,r11
        andi.   r11,r14,_PAGE_DIRTY
        rlwimi  r15,r14,32-2,26,31      /* Move in BAP bits */

        /* Mask out SW and UW if !DIRTY (XXX optimize this !) */
        bne     1f
        li      r11,MAS3_SW|MAS3_UW
        andc    r15,r15,r11
1:
        mtspr   SPRN_MAS7_MAS3,r15
        tlbwe

tlb_miss_done_bolted:
        tlb_epilog_bolted
        rfi

itlb_miss_kernel_bolted:
        li      r11,_PAGE_PRESENT|_PAGE_BAP_SX  /* Base perm */
        oris    r11,r11,_PAGE_ACCESSED@h
tlb_miss_kernel_bolted:
        mfspr   r10,SPRN_MAS1
        ld      r14,PACA_KERNELPGD(r13)
        srdi    r15,r16,44              /* get kernel region */
        andi.   r15,r15,1               /* Check for vmalloc region */
        rlwinm  r10,r10,0,16,1          /* Clear TID */
        mtspr   SPRN_MAS1,r10
        bne+    tlb_miss_common_bolted

tlb_miss_fault_bolted:
        /* We need to check if it was an instruction miss */
        andi.   r10,r11,_PAGE_BAP_UX|_PAGE_BAP_SX
        bne     itlb_miss_fault_bolted
dtlb_miss_fault_bolted:
        tlb_epilog_bolted
        b       exc_data_storage_book3e
itlb_miss_fault_bolted:
        tlb_epilog_bolted
        b       exc_instruction_storage_book3e

/* Instruction TLB miss */
        START_EXCEPTION(instruction_tlb_miss_bolted)
        tlb_prolog_bolted BOOKE_INTERRUPT_ITLB_MISS SPRN_SRR0

        rldicl. r10,r16,64-PGTABLE_EADDR_SIZE,PGTABLE_EADDR_SIZE+4
        srdi    r15,r16,60              /* get region */
        bne-    itlb_miss_fault_bolted

        li      r11,_PAGE_PRESENT|_PAGE_BAP_UX  /* Base perm */

        /* We do the user/kernel test for the PID here along with the RW test
         */

        cmpldi  cr0,r15,0                       /* Check for user region */
        oris    r11,r11,_PAGE_ACCESSED@h
        beq     tlb_miss_user_bolted
        b       itlb_miss_kernel_bolted

/*
 * TLB miss handling for e6500 and derivatives, using hardware tablewalk.
 *
 * Linear mapping is bolted: no virtual page table or nested TLB misses
 * Indirect entries in TLB1, hardware loads resulting direct entries
 *    into TLB0
 * No HES or NV hint on TLB1, so we need to do software round-robin
 * No tlbsrx. so we need a spinlock, and we have to deal
 *    with MAS-damage caused by tlbsx
 * 4K pages only
 */

        START_EXCEPTION(instruction_tlb_miss_e6500)
        tlb_prolog_bolted BOOKE_INTERRUPT_ITLB_MISS SPRN_SRR0

        ld      r11,PACA_TCD_PTR(r13)
        srdi.   r15,r16,60              /* get region */
        ori     r16,r16,1

        bne     tlb_miss_kernel_e6500   /* user/kernel test */

        b       tlb_miss_common_e6500

        START_EXCEPTION(data_tlb_miss_e6500)
        tlb_prolog_bolted BOOKE_INTERRUPT_DTLB_MISS SPRN_DEAR

        ld      r11,PACA_TCD_PTR(r13)
        srdi.   r15,r16,60              /* get region */
        rldicr  r16,r16,0,62

        bne     tlb_miss_kernel_e6500   /* user vs kernel check */

/*
 * This is the guts of the TLB miss handler for e6500 and derivatives.
 * We are entered with:
 *
 * r16 = page of faulting address (low bit 0 if data, 1 if instruction)
 * r15 = crap (free to use)
 * r14 = page table base
 * r13 = PACA
 * r11 = tlb_per_core ptr
 * r10 = crap (free to use)
 * r7  = esel_next
 */
tlb_miss_common_e6500:
        crmove  cr2*4+2,cr0*4+2         /* cr2.eq != 0 if kernel address */

BEGIN_FTR_SECTION               /* CPU_FTR_SMT */
        /*
         * Search if we already have an indirect entry for that virtual
         * address, and if we do, bail out.
         *
         * MAS6:IND should be already set based on MAS4
         */
        lhz     r10,PACAPACAINDEX(r13)
        addi    r10,r10,1
        crclr   cr1*4+eq        /* set cr1.eq = 0 for non-recursive */
1:      lbarx   r15,0,r11
        cmpdi   r15,0
        bne     2f
        stbcx.  r10,0,r11
        bne     1b
3:
        .subsection 1
2:      cmpd    cr1,r15,r10     /* recursive lock due to mcheck/crit/etc? */
        beq     cr1,3b          /* unlock will happen if cr1.eq = 0 */
10:     lbz     r15,0(r11)
        cmpdi   r15,0
        bne     10b
        b       1b
        .previous
END_FTR_SECTION_IFSET(CPU_FTR_SMT)

        lbz     r7,TCD_ESEL_NEXT(r11)

BEGIN_FTR_SECTION               /* CPU_FTR_SMT */
        /*
         * Erratum A-008139 says that we can't use tlbwe to change
         * an indirect entry in any way (including replacing or
         * invalidating) if the other thread could be in the process
         * of a lookup.  The workaround is to invalidate the entry
         * with tlbilx before overwriting.
         */

        rlwinm  r10,r7,16,0xff0000
        oris    r10,r10,MAS0_TLBSEL(1)@h
        mtspr   SPRN_MAS0,r10
        isync
        tlbre
        mfspr   r15,SPRN_MAS1
        andis.  r15,r15,MAS1_VALID@h
        beq     5f

BEGIN_FTR_SECTION_NESTED(532)
        mfspr   r10,SPRN_MAS8
        rlwinm  r10,r10,0,0x80000fff  /* tgs,tlpid -> sgs,slpid */
        mtspr   SPRN_MAS5,r10
END_FTR_SECTION_NESTED(CPU_FTR_EMB_HV,CPU_FTR_EMB_HV,532)

        mfspr   r10,SPRN_MAS1
        rlwinm  r15,r10,0,0x3fff0000  /* tid -> spid */
        rlwimi  r15,r10,20,0x00000003 /* ind,ts -> sind,sas */
        mfspr   r10,SPRN_MAS6
        mtspr   SPRN_MAS6,r15

        mfspr   r15,SPRN_MAS2
        isync
        PPC_TLBILX_VA(0,R15)
        isync

        mtspr   SPRN_MAS6,r10

5:
BEGIN_FTR_SECTION_NESTED(532)
        li      r10,0
        mtspr   SPRN_MAS8,r10
        mtspr   SPRN_MAS5,r10
END_FTR_SECTION_NESTED(CPU_FTR_EMB_HV,CPU_FTR_EMB_HV,532)

        tlbsx   0,r16
        mfspr   r10,SPRN_MAS1
        andis.  r15,r10,MAS1_VALID@h
        bne     tlb_miss_done_e6500
FTR_SECTION_ELSE
        mfspr   r10,SPRN_MAS1
ALT_FTR_SECTION_END_IFSET(CPU_FTR_SMT)

        oris    r10,r10,MAS1_VALID@h
        beq     cr2,4f
        rlwinm  r10,r10,0,16,1          /* Clear TID */
4:      mtspr   SPRN_MAS1,r10

        /* Now, we need to walk the page tables. First check if we are in
         * range.
         */
        rldicl. r10,r16,64-PGTABLE_EADDR_SIZE,PGTABLE_EADDR_SIZE+4
        bne-    tlb_miss_fault_e6500

        rldicl  r15,r16,64-PGDIR_SHIFT+3,64-PGD_INDEX_SIZE-3
        cmpldi  cr0,r14,0
        clrrdi  r15,r15,3
        beq-    tlb_miss_fault_e6500 /* No PGDIR, bail */
        ldx     r14,r14,r15             /* grab pgd entry */

        rldicl  r15,r16,64-PUD_SHIFT+3,64-PUD_INDEX_SIZE-3
        clrrdi  r15,r15,3
        cmpdi   cr0,r14,0
        bge     tlb_miss_huge_e6500     /* Bad pgd entry or hugepage; bail */
        ldx     r14,r14,r15             /* grab pud entry */

        rldicl  r15,r16,64-PMD_SHIFT+3,64-PMD_INDEX_SIZE-3
        clrrdi  r15,r15,3
        cmpdi   cr0,r14,0
        bge     tlb_miss_huge_e6500
        ldx     r14,r14,r15             /* Grab pmd entry */

        mfspr   r10,SPRN_MAS0
        cmpdi   cr0,r14,0
        bge     tlb_miss_huge_e6500

        /* Now we build the MAS for a 2M indirect page:
         *
         * MAS 0   :    ESEL needs to be filled by software round-robin
         * MAS 1   :    Fully set up
         *               - PID already updated by caller if necessary
         *               - TSIZE for now is base ind page size always
         *               - TID already cleared if necessary
         * MAS 2   :    Default not 2M-aligned, need to be redone
         * MAS 3+7 :    Needs to be done
         */

        ori     r14,r14,(BOOK3E_PAGESZ_4K << MAS3_SPSIZE_SHIFT)
        mtspr   SPRN_MAS7_MAS3,r14

        clrrdi  r15,r16,21              /* make EA 2M-aligned */
        mtspr   SPRN_MAS2,r15

tlb_miss_huge_done_e6500:
        lbz     r16,TCD_ESEL_MAX(r11)
        lbz     r14,TCD_ESEL_FIRST(r11)
        rlwimi  r10,r7,16,0x00ff0000    /* insert esel_next into MAS0 */
        addi    r7,r7,1                 /* increment esel_next */
        mtspr   SPRN_MAS0,r10
        cmpw    r7,r16
        iseleq  r7,r14,r7               /* if next == last use first */
        stb     r7,TCD_ESEL_NEXT(r11)

        tlbwe

tlb_miss_done_e6500:
        .macro  tlb_unlock_e6500
BEGIN_FTR_SECTION
        beq     cr1,1f          /* no unlock if lock was recursively grabbed */
        li      r15,0
        isync
        stb     r15,0(r11)
1:
END_FTR_SECTION_IFSET(CPU_FTR_SMT)
        .endm

        tlb_unlock_e6500
        tlb_epilog_bolted
        rfi

tlb_miss_huge_e6500:
        beq     tlb_miss_fault_e6500
        rlwinm  r15,r14,32-_PAGE_PSIZE_SHIFT,0x1e

        /*
         * Now we build the MAS for a huge page.
         *
         * MAS 0   :    ESEL needs to be filled by software round-robin
         *               - can be handled by indirect code
         * MAS 1   :    Need to clear IND and set TSIZE
         * MAS 2,3+7:   Needs to be redone similar to non-tablewalk handler
         */

        mfspr   r10,SPRN_MAS1
        rlwinm  r10,r10,0,~MAS1_IND
        rlwimi  r10,r15,MAS1_TSIZE_SHIFT,MAS1_TSIZE_MASK
        mtspr   SPRN_MAS1,r10

        li      r10,-0x400
        sld     r15,r10,r15             /* Generate mask based on size */
        and     r10,r16,r15
        rldicr  r15,r14,64-(PTE_RPN_SHIFT-PAGE_SHIFT),63-PAGE_SHIFT
        rlwimi  r10,r14,32-19,27,31     /* Insert WIMGE */
        clrldi  r15,r15,PAGE_SHIFT      /* Clear crap at the top */
        rlwimi  r15,r14,32-8,22,25      /* Move in U bits */
        mtspr   SPRN_MAS2,r10
        andi.   r10,r14,_PAGE_DIRTY
        rlwimi  r15,r14,32-2,26,31      /* Move in BAP bits */

        /* Mask out SW and UW if !DIRTY (XXX optimize this !) */
        bne     1f
        li      r10,MAS3_SW|MAS3_UW
        andc    r15,r15,r10
1:
        mtspr   SPRN_MAS7_MAS3,r15

        mfspr   r10,SPRN_MAS0
        b       tlb_miss_huge_done_e6500

tlb_miss_kernel_e6500:
        ld      r14,PACA_KERNELPGD(r13)
        srdi    r15,r16,44              /* get kernel region */
        xoris   r15,r15,0xc             /* Check for vmalloc region */
        cmplwi  cr1,r15,1
        beq+    cr1,tlb_miss_common_e6500

tlb_miss_fault_e6500:
        tlb_unlock_e6500
        /* We need to check if it was an instruction miss */
        andi.   r16,r16,1
        bne     itlb_miss_fault_e6500
dtlb_miss_fault_e6500:
        tlb_epilog_bolted
        b       exc_data_storage_book3e
itlb_miss_fault_e6500:
        tlb_epilog_bolted
        b       exc_instruction_storage_book3e

/*
 * This is the guts of the second-level TLB miss handler for direct
 * misses. We are entered with:
 *
 * r16 = virtual page table faulting address
 * r15 = region (top 4 bits of address)
 * r14 = crap (free to use)
 * r13 = PACA
 * r12 = TLB exception frame in PACA
 * r11 = crap (free to use)
 * r10 = crap (free to use)
 *
 * Note that this should only ever be called as a second level handler
 * with the current scheme when using SW load.
 * That means we can always get the original fault DEAR at
 * EX_TLB_DEAR-EX_TLB_SIZE(r12)
 *
 * It can be re-entered by the linear mapping miss handler. However, to
 * avoid too much complication, it will restart the whole fault at level
 * 0 so we don't care too much about clobbers
 *
 * XXX That code was written back when we couldn't clobber r14. We can now,
 * so we could probably optimize things a bit
 */
virt_page_table_tlb_miss:
        /* Are we hitting a kernel page table ? */
        srdi    r15,r16,60
        andi.   r10,r15,0x8

        /* The cool thing now is that r10 contains 0 for user and 8 for kernel,
         * and we happen to have the swapper_pg_dir at offset 8 from the user
         * pgdir in the PACA :-).
         */
        add     r11,r10,r13

        /* If kernel, we need to clear MAS1 TID */
        beq     1f
        /* XXX replace the RMW cycles with immediate loads + writes */
        mfspr   r10,SPRN_MAS1
        rlwinm  r10,r10,0,16,1                  /* Clear TID */
        mtspr   SPRN_MAS1,r10
#ifdef CONFIG_PPC_KUAP
        b       2f
1:
        mfspr   r10,SPRN_MAS1
        rlwinm. r10,r10,0,0x3fff0000
        beq-    virt_page_table_tlb_miss_fault /* KUAP fault */
2:
#else
1:
#endif

        /* Now, we need to walk the page tables. First check if we are in
         * range.
         */
        rldicl  r10,r16,64-(VPTE_INDEX_SIZE+3),VPTE_INDEX_SIZE+3+4
        cmpldi  r10,0x80
        bne-    virt_page_table_tlb_miss_fault

        /* Get the PGD pointer */
        ld      r15,PACAPGD(r11)
        cmpldi  cr0,r15,0
        beq-    virt_page_table_tlb_miss_fault

        /* Get to PGD entry */
        rldicl  r11,r16,64-VPTE_PGD_SHIFT,64-PGD_INDEX_SIZE-3
        clrrdi  r10,r11,3
        ldx     r15,r10,r15
        cmpdi   cr0,r15,0
        bge     virt_page_table_tlb_miss_fault

        /* Get to PUD entry */
        rldicl  r11,r16,64-VPTE_PUD_SHIFT,64-PUD_INDEX_SIZE-3
        clrrdi  r10,r11,3
        ldx     r15,r10,r15
        cmpdi   cr0,r15,0
        bge     virt_page_table_tlb_miss_fault

        /* Get to PMD entry */
        rldicl  r11,r16,64-VPTE_PMD_SHIFT,64-PMD_INDEX_SIZE-3
        clrrdi  r10,r11,3
        ldx     r15,r10,r15
        cmpdi   cr0,r15,0
        bge     virt_page_table_tlb_miss_fault

        /* Ok, we're all right, we can now create a kernel translation for
         * a 4K or 64K page from r16 -> r15.
         */
        /* Now we build the MAS:
         *
         * MAS 0   :    Fully setup with defaults in MAS4 and TLBnCFG
         * MAS 1   :    Almost fully setup
         *               - PID already updated by caller if necessary
         *               - TSIZE for now is base page size always
         * MAS 2   :    Use defaults
         * MAS 3+7 :    Needs to be done
         *
         * So we only do MAS 2 and 3 for now...
         */
        clrldi  r11,r15,4               /* remove region ID from RPN */
        ori     r10,r11,1               /* Or-in SR */

        srdi    r16,r10,32
        mtspr   SPRN_MAS3,r10
        mtspr   SPRN_MAS7,r16

        tlbwe

        /* Return to caller, normal case */
        TLB_MISS_EPILOG_SUCCESS
        rfi

virt_page_table_tlb_miss_fault:
        /* If we fault here, things are a little bit tricky. We need to call
         * either data or instruction store fault, and we need to retrieve
         * the original fault address and ESR (for data).
         *
         * The thing is, we know that in normal circumstances, this is
         * always called as a second level tlb miss for SW load or as a first
         * level TLB miss for HW load, so we should be able to peek at the
         * relevant information in the first exception frame in the PACA.
         *
         * However, we do need to double check that, because we may just hit
         * a stray kernel pointer or a userland attack trying to hit those
         * areas. If that is the case, we do a data fault. (We can't get here
         * from an instruction tlb miss anyway).
         *
         * Note also that when going to a fault, we must unwind the previous
         * level as well. Since we are doing that, we don't need to clear or
         * restore the TLB reservation neither.
         */
        subf    r10,r13,r12
        cmpldi  cr0,r10,PACA_EXTLB+EX_TLB_SIZE
        bne-    virt_page_table_tlb_miss_whacko_fault

        /* We dig the original DEAR and ESR from slot 0 */
        ld      r15,EX_TLB_DEAR+PACA_EXTLB(r13)
        ld      r16,EX_TLB_ESR+PACA_EXTLB(r13)

        /* We check for the "special" ESR value for instruction faults */
        cmpdi   cr0,r16,-1
        beq     1f
        mtspr   SPRN_DEAR,r15
        mtspr   SPRN_ESR,r16
        TLB_MISS_EPILOG_ERROR
        b       exc_data_storage_book3e
1:      TLB_MISS_EPILOG_ERROR
        b       exc_instruction_storage_book3e

virt_page_table_tlb_miss_whacko_fault:
        /* The linear fault will restart everything so ESR and DEAR will
         * not have been clobbered, let's just fault with what we have
         */
        TLB_MISS_EPILOG_ERROR
        b       exc_data_storage_book3e

/*
 * This is the guts of "any" level TLB miss handler for kernel linear
 * mapping misses. We are entered with:
 *
 *
 * r16 = faulting address
 * r15 = crap (free to use)
 * r14 = ESR (data) or -1 (instruction)
 * r13 = PACA
 * r12 = TLB exception frame in PACA
 * r11 = crap (free to use)
 * r10 = crap (free to use)
 *
 * In addition we know that we will not re-enter, so in theory, we could
 * use a simpler epilog not restoring SRR0/1 etc.. but we'll do that later.
 *
 * We also need to be careful about MAS registers here & TLB reservation,
 * as we know we'll have clobbered them if we interrupt the main TLB miss
 * handlers in which case we probably want to do a full restart at level
 * 0 rather than saving / restoring the MAS.
 *
 * Note: If we care about performance of that core, we can easily shuffle
 *       a few things around
 */
tlb_load_linear:
        /* For now, we assume the linear mapping is contiguous and stops at
         * linear_map_top. We also assume the size is a multiple of 1G, thus
         * we only use 1G pages for now. That might have to be changed in a
         * final implementation, especially when dealing with hypervisors
         */
        __LOAD_PACA_TOC(r11)
        LOAD_REG_ADDR_ALTTOC(r11, r11, linear_map_top)
        ld      r10,0(r11)
        tovirt(10,10)
        cmpld   cr0,r16,r10
        bge     tlb_load_linear_fault

        /* MAS1 need whole new setup. */
        li      r15,(BOOK3E_PAGESZ_1GB<<MAS1_TSIZE_SHIFT)
        oris    r15,r15,MAS1_VALID@h    /* MAS1 needs V and TSIZE */
        mtspr   SPRN_MAS1,r15

        /* Already somebody there ? */
        PPC_TLBSRX_DOT(0,R16)
        beq     tlb_load_linear_done

        /* Now we build the remaining MAS. MAS0 and 2 should be fine
         * with their defaults, which leaves us with MAS 3 and 7. The
         * mapping is linear, so we just take the address, clear the
         * region bits, and or in the permission bits which are currently
         * hard wired
         */
        clrrdi  r10,r16,30              /* 1G page index */
        clrldi  r10,r10,4               /* clear region bits */
        ori     r10,r10,MAS3_SR|MAS3_SW|MAS3_SX

        srdi    r16,r10,32
        mtspr   SPRN_MAS3,r10
        mtspr   SPRN_MAS7,r16

        tlbwe

tlb_load_linear_done:
        /* We use the "error" epilog for success as we do want to
         * restore to the initial faulting context, whatever it was.
         * We do that because we can't resume a fault within a TLB
         * miss handler, due to MAS and TLB reservation being clobbered.
         */
        TLB_MISS_EPILOG_ERROR
        rfi

tlb_load_linear_fault:
        /* We keep the DEAR and ESR around, this shouldn't have happened */
        cmpdi   cr0,r14,-1
        beq     1f
        TLB_MISS_EPILOG_ERROR_SPECIAL
        b       exc_data_storage_book3e
1:      TLB_MISS_EPILOG_ERROR_SPECIAL
        b       exc_instruction_storage_book3e