/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Synthesize TLB refill handlers at runtime.
 *
 * Copyright (C) 2004, 2005, 2006, 2008  Thiemo Seufer
 * Copyright (C) 2005, 2007, 2008, 2009  Maciej W. Rozycki
 * Copyright (C) 2006  Ralf Baechle (ralf@linux-mips.org)
 * Copyright (C) 2008, 2009 Cavium Networks, Inc.
 * Copyright (C) 2011  MIPS Technologies, Inc.
 *
 * ... and the days got worse and worse and now you see
 * I've gone completely out of my mind.
 *
 * They're coming to take me a away haha
 * they're coming to take me a away hoho hihi haha
 * to the funny farm where code is beautiful all the time ...
 *
 * (Condolences to Napoleon XIV)
 */

#include <linux/bug.h>
#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/smp.h>
#include <linux/string.h>
#include <linux/cache.h>
#include <linux/pgtable.h>

#include <asm/cacheflush.h>
#include <asm/cpu-type.h>
#include <asm/mmu_context.h>
#include <asm/war.h>
#include <asm/uasm.h>
#include <asm/setup.h>
#include <asm/tlbex.h>

static int mips_xpa_disabled;

static int __init xpa_disable(char *s)
{
        mips_xpa_disabled = 1;

        return 1;
}

__setup("noxpa", xpa_disable);

/*
 * TLB load/store/modify handlers.
 *
 * Only the fastpath gets synthesized at runtime, the slowpath for
 * do_page_fault remains normal asm.
 */
extern void tlb_do_page_fault_0(void);
extern void tlb_do_page_fault_1(void);

struct work_registers {
        int r1;
        int r2;
        int r3;
};

struct tlb_reg_save {
        unsigned long a;
        unsigned long b;
} ____cacheline_aligned_in_smp;

static struct tlb_reg_save handler_reg_save[NR_CPUS];

static inline int r45k_bvahwbug(void)
{
        /* XXX: We should probe for the presence of this bug, but we don't. */
        return 0;
}

static inline int r4k_250MHZhwbug(void)
{
        /* XXX: We should probe for the presence of this bug, but we don't. */
        return 0;
}

extern int sb1250_m3_workaround_needed(void);

static inline int __maybe_unused bcm1250_m3_war(void)
{
        if (IS_ENABLED(CONFIG_SB1_PASS_2_WORKAROUNDS))
                return sb1250_m3_workaround_needed();
        return 0;
}

static inline int __maybe_unused r10000_llsc_war(void)
{
        return IS_ENABLED(CONFIG_WAR_R10000_LLSC);
}

static int use_bbit_insns(void)
{
        switch (current_cpu_type()) {
        case CPU_CAVIUM_OCTEON:
        case CPU_CAVIUM_OCTEON_PLUS:
        case CPU_CAVIUM_OCTEON2:
        case CPU_CAVIUM_OCTEON3:
                return 1;
        default:
                return 0;
        }
}

static int use_lwx_insns(void)
{
        switch (current_cpu_type()) {
        case CPU_CAVIUM_OCTEON2:
        case CPU_CAVIUM_OCTEON3:
                return 1;
        default:
                return 0;
        }
}
#if defined(CONFIG_CAVIUM_OCTEON_CVMSEG_SIZE) && \
    CONFIG_CAVIUM_OCTEON_CVMSEG_SIZE > 0
static bool scratchpad_available(void)
{
        return true;
}
static int scratchpad_offset(int i)
{
        /*
         * CVMSEG starts at address -32768 and extends for
         * CAVIUM_OCTEON_CVMSEG_SIZE 128 byte cache lines.
         */
        i += 1; /* Kernel use starts at the top and works down. */
        return CONFIG_CAVIUM_OCTEON_CVMSEG_SIZE * 128 - (8 * i) - 32768;
}
#else
static bool scratchpad_available(void)
{
        return false;
}
static int scratchpad_offset(int i)
{
        BUG();
        /* Really unreachable, but evidently some GCC want this. */
        return 0;
}
#endif
/*
 * Found by experiment: At least some revisions of the 4kc throw under
 * some circumstances a machine check exception, triggered by invalid
 * values in the index register.  Delaying the tlbp instruction until
 * after the next branch,  plus adding an additional nop in front of
 * tlbwi/tlbwr avoids the invalid index register values. Nobody knows
 * why; it's not an issue caused by the core RTL.
 *
 */
static int m4kc_tlbp_war(void)
{
        return current_cpu_type() == CPU_4KC;
}

/* Handle labels (which must be positive integers). */
enum label_id {
        label_second_part = 1,
        label_leave,
        label_vmalloc,
        label_vmalloc_done,
        label_tlbw_hazard_0,
        label_split = label_tlbw_hazard_0 + 8,
        label_tlbl_goaround1,
        label_tlbl_goaround2,
        label_nopage_tlbl,
        label_nopage_tlbs,
        label_nopage_tlbm,
        label_smp_pgtable_change,
        label_r3000_write_probe_fail,
        label_large_segbits_fault,
#ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
        label_tlb_huge_update,
#endif
};

UASM_L_LA(_second_part)
UASM_L_LA(_leave)
UASM_L_LA(_vmalloc)
UASM_L_LA(_vmalloc_done)
/* _tlbw_hazard_x is handled differently.  */
UASM_L_LA(_split)
UASM_L_LA(_tlbl_goaround1)
UASM_L_LA(_tlbl_goaround2)
UASM_L_LA(_nopage_tlbl)
UASM_L_LA(_nopage_tlbs)
UASM_L_LA(_nopage_tlbm)
UASM_L_LA(_smp_pgtable_change)
UASM_L_LA(_r3000_write_probe_fail)
UASM_L_LA(_large_segbits_fault)
#ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
UASM_L_LA(_tlb_huge_update)
#endif

static int hazard_instance;

static void uasm_bgezl_hazard(u32 **p, struct uasm_reloc **r, int instance)
{
        switch (instance) {
        case 0 ... 7:
                uasm_il_bgezl(p, r, 0, label_tlbw_hazard_0 + instance);
                return;
        default:
                BUG();
        }
}

static void uasm_bgezl_label(struct uasm_label **l, u32 **p, int instance)
{
        switch (instance) {
        case 0 ... 7:
                uasm_build_label(l, *p, label_tlbw_hazard_0 + instance);
                break;
        default:
                BUG();
        }
}

/*
 * pgtable bits are assigned dynamically depending on processor feature
 * and statically based on kernel configuration.  This spits out the actual
 * values the kernel is using.  Required to make sense from disassembled
 * TLB exception handlers.
 */
static void output_pgtable_bits_defines(void)
{
#define pr_define(fmt, ...)                                     \
        pr_debug("#define " fmt, ##__VA_ARGS__)

        pr_debug("#include <asm/asm.h>\n");
        pr_debug("#include <asm/regdef.h>\n");
        pr_debug("\n");

        pr_define("_PAGE_PRESENT_SHIFT %d\n", _PAGE_PRESENT_SHIFT);
        pr_define("_PAGE_NO_READ_SHIFT %d\n", _PAGE_NO_READ_SHIFT);
        pr_define("_PAGE_WRITE_SHIFT %d\n", _PAGE_WRITE_SHIFT);
        pr_define("_PAGE_ACCESSED_SHIFT %d\n", _PAGE_ACCESSED_SHIFT);
        pr_define("_PAGE_MODIFIED_SHIFT %d\n", _PAGE_MODIFIED_SHIFT);
#ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
        pr_define("_PAGE_HUGE_SHIFT %d\n", _PAGE_HUGE_SHIFT);
#endif
#ifdef _PAGE_NO_EXEC_SHIFT
        if (cpu_has_rixi)
                pr_define("_PAGE_NO_EXEC_SHIFT %d\n", _PAGE_NO_EXEC_SHIFT);
#endif
        pr_define("_PAGE_GLOBAL_SHIFT %d\n", _PAGE_GLOBAL_SHIFT);
        pr_define("_PAGE_VALID_SHIFT %d\n", _PAGE_VALID_SHIFT);
        pr_define("_PAGE_DIRTY_SHIFT %d\n", _PAGE_DIRTY_SHIFT);
        pr_define("_PFN_SHIFT %d\n", _PFN_SHIFT);
        pr_debug("\n");
}

static inline void dump_handler(const char *symbol, const void *start, const void *end)
{
        unsigned int count = (end - start) / sizeof(u32);
        const u32 *handler = start;
        int i;

        pr_debug("LEAF(%s)\n", symbol);

        pr_debug("\t.set push\n");
        pr_debug("\t.set noreorder\n");

        for (i = 0; i < count; i++)
                pr_debug("\t.word\t0x%08x\t\t# %p\n", handler[i], &handler[i]);

        pr_debug("\t.set\tpop\n");

        pr_debug("\tEND(%s)\n", symbol);
}

/* The only general purpose registers allowed in TLB handlers. */
#define K0              26
#define K1              27

/* Some CP0 registers */
#define C0_INDEX        0, 0
#define C0_ENTRYLO0     2, 0
#define C0_TCBIND       2, 2
#define C0_ENTRYLO1     3, 0
#define C0_CONTEXT      4, 0
#define C0_PAGEMASK     5, 0
#define C0_PWBASE       5, 5
#define C0_PWFIELD      5, 6
#define C0_PWSIZE       5, 7
#define C0_PWCTL        6, 6
#define C0_BADVADDR     8, 0
#define C0_PGD          9, 7
#define C0_ENTRYHI      10, 0
#define C0_EPC          14, 0
#define C0_XCONTEXT     20, 0

#ifdef CONFIG_64BIT
# define GET_CONTEXT(buf, reg) UASM_i_MFC0(buf, reg, C0_XCONTEXT)
#else
# define GET_CONTEXT(buf, reg) UASM_i_MFC0(buf, reg, C0_CONTEXT)
#endif

/* The worst case length of the handler is around 18 instructions for
 * R3000-style TLBs and up to 63 instructions for R4000-style TLBs.
 * Maximum space available is 32 instructions for R3000 and 64
 * instructions for R4000.
 *
 * We deliberately chose a buffer size of 128, so we won't scribble
 * over anything important on overflow before we panic.
 */
static u32 tlb_handler[128];

/* simply assume worst case size for labels and relocs */
static struct uasm_label labels[128];
static struct uasm_reloc relocs[128];

static int check_for_high_segbits;
static bool fill_includes_sw_bits;

static unsigned int kscratch_used_mask;

static inline int __maybe_unused c0_kscratch(void)
{
        switch (current_cpu_type()) {
        case CPU_XLP:
        case CPU_XLR:
                return 22;
        default:
                return 31;
        }
}

static int allocate_kscratch(void)
{
        int r;
        unsigned int a = cpu_data[0].kscratch_mask & ~kscratch_used_mask;

        r = ffs(a);

        if (r == 0)
                return -1;

        r--; /* make it zero based */

        kscratch_used_mask |= (1 << r);

        return r;
}

static int scratch_reg;
int pgd_reg;
EXPORT_SYMBOL_GPL(pgd_reg);
enum vmalloc64_mode {not_refill, refill_scratch, refill_noscratch};

static struct work_registers build_get_work_registers(u32 **p)
{
        struct work_registers r;

        if (scratch_reg >= 0) {
                /* Save in CPU local C0_KScratch? */
                UASM_i_MTC0(p, 1, c0_kscratch(), scratch_reg);
                r.r1 = K0;
                r.r2 = K1;
                r.r3 = 1;
                return r;
        }

        if (num_possible_cpus() > 1) {
                /* Get smp_processor_id */
                UASM_i_CPUID_MFC0(p, K0, SMP_CPUID_REG);
                UASM_i_SRL_SAFE(p, K0, K0, SMP_CPUID_REGSHIFT);

                /* handler_reg_save index in K0 */
                UASM_i_SLL(p, K0, K0, ilog2(sizeof(struct tlb_reg_save)));

                UASM_i_LA(p, K1, (long)&handler_reg_save);
                UASM_i_ADDU(p, K0, K0, K1);
        } else {
                UASM_i_LA(p, K0, (long)&handler_reg_save);
        }
        /* K0 now points to save area, save $1 and $2  */
        UASM_i_SW(p, 1, offsetof(struct tlb_reg_save, a), K0);
        UASM_i_SW(p, 2, offsetof(struct tlb_reg_save, b), K0);

        r.r1 = K1;
        r.r2 = 1;
        r.r3 = 2;
        return r;
}

static void build_restore_work_registers(u32 **p)
{
        if (scratch_reg >= 0) {
                uasm_i_ehb(p);
                UASM_i_MFC0(p, 1, c0_kscratch(), scratch_reg);
                return;
        }
        /* K0 already points to save area, restore $1 and $2  */
        UASM_i_LW(p, 1, offsetof(struct tlb_reg_save, a), K0);
        UASM_i_LW(p, 2, offsetof(struct tlb_reg_save, b), K0);
}

#ifndef CONFIG_MIPS_PGD_C0_CONTEXT

/*
 * CONFIG_MIPS_PGD_C0_CONTEXT implies 64 bit and lack of pgd_current,
 * we cannot do r3000 under these circumstances.
 *
 * The R3000 TLB handler is simple.
 */
static void build_r3000_tlb_refill_handler(void)
{
        long pgdc = (long)pgd_current;
        u32 *p;

        memset(tlb_handler, 0, sizeof(tlb_handler));
        p = tlb_handler;

        uasm_i_mfc0(&p, K0, C0_BADVADDR);
        uasm_i_lui(&p, K1, uasm_rel_hi(pgdc)); /* cp0 delay */
        uasm_i_lw(&p, K1, uasm_rel_lo(pgdc), K1);
        uasm_i_srl(&p, K0, K0, 22); /* load delay */
        uasm_i_sll(&p, K0, K0, 2);
        uasm_i_addu(&p, K1, K1, K0);
        uasm_i_mfc0(&p, K0, C0_CONTEXT);
        uasm_i_lw(&p, K1, 0, K1); /* cp0 delay */
        uasm_i_andi(&p, K0, K0, 0xffc); /* load delay */
        uasm_i_addu(&p, K1, K1, K0);
        uasm_i_lw(&p, K0, 0, K1);
        uasm_i_nop(&p); /* load delay */
        uasm_i_mtc0(&p, K0, C0_ENTRYLO0);
        uasm_i_mfc0(&p, K1, C0_EPC); /* cp0 delay */
        uasm_i_tlbwr(&p); /* cp0 delay */
        uasm_i_jr(&p, K1);
        uasm_i_rfe(&p); /* branch delay */

        if (p > tlb_handler + 32)
                panic("TLB refill handler space exceeded");

        pr_debug("Wrote TLB refill handler (%u instructions).\n",
                 (unsigned int)(p - tlb_handler));

        memcpy((void *)ebase, tlb_handler, 0x80);
        local_flush_icache_range(ebase, ebase + 0x80);
        dump_handler("r3000_tlb_refill", (u32 *)ebase, (u32 *)(ebase + 0x80));
}
#endif /* CONFIG_MIPS_PGD_C0_CONTEXT */

/*
 * The R4000 TLB handler is much more complicated. We have two
 * consecutive handler areas with 32 instructions space each.
 * Since they aren't used at the same time, we can overflow in the
 * other one.To keep things simple, we first assume linear space,
 * then we relocate it to the final handler layout as needed.
 */
static u32 final_handler[64];

/*
 * Hazards
 *
 * From the IDT errata for the QED RM5230 (Nevada), processor revision 1.0:
 * 2. A timing hazard exists for the TLBP instruction.
 *
 *      stalling_instruction
 *      TLBP
 *
 * The JTLB is being read for the TLBP throughout the stall generated by the
 * previous instruction. This is not really correct as the stalling instruction
 * can modify the address used to access the JTLB.  The failure symptom is that
 * the TLBP instruction will use an address created for the stalling instruction
 * and not the address held in C0_ENHI and thus report the wrong results.
 *
 * The software work-around is to not allow the instruction preceding the TLBP
 * to stall - make it an NOP or some other instruction guaranteed not to stall.
 *
 * Errata 2 will not be fixed.  This errata is also on the R5000.
 *
 * As if we MIPS hackers wouldn't know how to nop pipelines happy ...
 */
static void __maybe_unused build_tlb_probe_entry(u32 **p)
{
        switch (current_cpu_type()) {
        /* Found by experiment: R4600 v2.0/R4700 needs this, too.  */
        case CPU_R4600:
        case CPU_R4700:
        case CPU_R5000:
        case CPU_NEVADA:
                uasm_i_nop(p);
                uasm_i_tlbp(p);
                break;

        default:
                uasm_i_tlbp(p);
                break;
        }
}

void build_tlb_write_entry(u32 **p, struct uasm_label **l,
                           struct uasm_reloc **r,
                           enum tlb_write_entry wmode)
{
        void(*tlbw)(u32 **) = NULL;

        switch (wmode) {
        case tlb_random: tlbw = uasm_i_tlbwr; break;
        case tlb_indexed: tlbw = uasm_i_tlbwi; break;
        }

        if (cpu_has_mips_r2_r6) {
                if (cpu_has_mips_r2_exec_hazard)
                        uasm_i_ehb(p);
                tlbw(p);
                return;
        }

        switch (current_cpu_type()) {
        case CPU_R4000PC:
        case CPU_R4000SC:
        case CPU_R4000MC:
        case CPU_R4400PC:
        case CPU_R4400SC:
        case CPU_R4400MC:
                /*
                 * This branch uses up a mtc0 hazard nop slot and saves
                 * two nops after the tlbw instruction.
                 */
                uasm_bgezl_hazard(p, r, hazard_instance);
                tlbw(p);
                uasm_bgezl_label(l, p, hazard_instance);
                hazard_instance++;
                uasm_i_nop(p);
                break;

        case CPU_R4600:
        case CPU_R4700:
                uasm_i_nop(p);
                tlbw(p);
                uasm_i_nop(p);
                break;

        case CPU_R5000:
        case CPU_NEVADA:
                uasm_i_nop(p); /* QED specifies 2 nops hazard */
                uasm_i_nop(p); /* QED specifies 2 nops hazard */
                tlbw(p);
                break;

        case CPU_5KC:
        case CPU_TX49XX:
        case CPU_PR4450:
        case CPU_XLR:
                uasm_i_nop(p);
                tlbw(p);
                break;

        case CPU_R10000:
        case CPU_R12000:
        case CPU_R14000:
        case CPU_R16000:
        case CPU_4KC:
        case CPU_4KEC:
        case CPU_M14KC:
        case CPU_M14KEC:
        case CPU_SB1:
        case CPU_SB1A:
        case CPU_4KSC:
        case CPU_20KC:
        case CPU_25KF:
        case CPU_BMIPS32:
        case CPU_BMIPS3300:
        case CPU_BMIPS4350:
        case CPU_BMIPS4380:
        case CPU_BMIPS5000:
        case CPU_LOONGSON2EF:
        case CPU_LOONGSON64:
        case CPU_R5500:
                if (m4kc_tlbp_war())
                        uasm_i_nop(p);
                fallthrough;
        case CPU_ALCHEMY:
                tlbw(p);
                break;

        case CPU_RM7000:
                uasm_i_nop(p);
                uasm_i_nop(p);
                uasm_i_nop(p);
                uasm_i_nop(p);
                tlbw(p);
                break;

        case CPU_VR4111:
        case CPU_VR4121:
        case CPU_VR4122:
        case CPU_VR4181:
        case CPU_VR4181A:
                uasm_i_nop(p);
                uasm_i_nop(p);
                tlbw(p);
                uasm_i_nop(p);
                uasm_i_nop(p);
                break;

        case CPU_VR4131:
        case CPU_VR4133:
                uasm_i_nop(p);
                uasm_i_nop(p);
                tlbw(p);
                break;

        case CPU_XBURST:
                tlbw(p);
                uasm_i_nop(p);
                break;

        default:
                panic("No TLB refill handler yet (CPU type: %d)",
                      current_cpu_type());
                break;
        }
}
EXPORT_SYMBOL_GPL(build_tlb_write_entry);

static __maybe_unused void build_convert_pte_to_entrylo(u32 **p,
                                                        unsigned int reg)
{
        if (_PAGE_GLOBAL_SHIFT == 0) {
                /* pte_t is already in EntryLo format */
                return;
        }

        if (cpu_has_rixi && !!_PAGE_NO_EXEC) {
                if (fill_includes_sw_bits) {
                        UASM_i_ROTR(p, reg, reg, ilog2(_PAGE_GLOBAL));
                } else {
                        UASM_i_SRL(p, reg, reg, ilog2(_PAGE_NO_EXEC));
                        UASM_i_ROTR(p, reg, reg,
                                    ilog2(_PAGE_GLOBAL) - ilog2(_PAGE_NO_EXEC));
                }
        } else {
#ifdef CONFIG_PHYS_ADDR_T_64BIT
                uasm_i_dsrl_safe(p, reg, reg, ilog2(_PAGE_GLOBAL));
#else
                UASM_i_SRL(p, reg, reg, ilog2(_PAGE_GLOBAL));
#endif
        }
}

#ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT

static void build_restore_pagemask(u32 **p, struct uasm_reloc **r,
                                   unsigned int tmp, enum label_id lid,
                                   int restore_scratch)
{
        if (restore_scratch) {
                /*
                 * Ensure the MFC0 below observes the value written to the
                 * KScratch register by the prior MTC0.
                 */
                if (scratch_reg >= 0)
                        uasm_i_ehb(p);

                /* Reset default page size */
                if (PM_DEFAULT_MASK >> 16) {
                        uasm_i_lui(p, tmp, PM_DEFAULT_MASK >> 16);
                        uasm_i_ori(p, tmp, tmp, PM_DEFAULT_MASK & 0xffff);
                        uasm_i_mtc0(p, tmp, C0_PAGEMASK);
                        uasm_il_b(p, r, lid);
                } else if (PM_DEFAULT_MASK) {
                        uasm_i_ori(p, tmp, 0, PM_DEFAULT_MASK);
                        uasm_i_mtc0(p, tmp, C0_PAGEMASK);
                        uasm_il_b(p, r, lid);
                } else {
                        uasm_i_mtc0(p, 0, C0_PAGEMASK);
                        uasm_il_b(p, r, lid);
                }
                if (scratch_reg >= 0)
                        UASM_i_MFC0(p, 1, c0_kscratch(), scratch_reg);
                else
                        UASM_i_LW(p, 1, scratchpad_offset(0), 0);
        } else {
                /* Reset default page size */
                if (PM_DEFAULT_MASK >> 16) {
                        uasm_i_lui(p, tmp, PM_DEFAULT_MASK >> 16);
                        uasm_i_ori(p, tmp, tmp, PM_DEFAULT_MASK & 0xffff);
                        uasm_il_b(p, r, lid);
                        uasm_i_mtc0(p, tmp, C0_PAGEMASK);
                } else if (PM_DEFAULT_MASK) {
                        uasm_i_ori(p, tmp, 0, PM_DEFAULT_MASK);
                        uasm_il_b(p, r, lid);
                        uasm_i_mtc0(p, tmp, C0_PAGEMASK);
                } else {
                        uasm_il_b(p, r, lid);
                        uasm_i_mtc0(p, 0, C0_PAGEMASK);
                }
        }
}

static void build_huge_tlb_write_entry(u32 **p, struct uasm_label **l,
                                       struct uasm_reloc **r,
                                       unsigned int tmp,
                                       enum tlb_write_entry wmode,
                                       int restore_scratch)
{
        /* Set huge page tlb entry size */
        uasm_i_lui(p, tmp, PM_HUGE_MASK >> 16);
        uasm_i_ori(p, tmp, tmp, PM_HUGE_MASK & 0xffff);
        uasm_i_mtc0(p, tmp, C0_PAGEMASK);

        build_tlb_write_entry(p, l, r, wmode);

        build_restore_pagemask(p, r, tmp, label_leave, restore_scratch);
}

/*
 * Check if Huge PTE is present, if so then jump to LABEL.
 */
static void
build_is_huge_pte(u32 **p, struct uasm_reloc **r, unsigned int tmp,
                  unsigned int pmd, int lid)
{
        UASM_i_LW(p, tmp, 0, pmd);
        if (use_bbit_insns()) {
                uasm_il_bbit1(p, r, tmp, ilog2(_PAGE_HUGE), lid);
        } else {
                uasm_i_andi(p, tmp, tmp, _PAGE_HUGE);
                uasm_il_bnez(p, r, tmp, lid);
        }
}

static void build_huge_update_entries(u32 **p, unsigned int pte,
                                      unsigned int tmp)
{
        int small_sequence;

        /*
         * A huge PTE describes an area the size of the
         * configured huge page size. This is twice the
         * of the large TLB entry size we intend to use.
         * A TLB entry half the size of the configured
         * huge page size is configured into entrylo0
         * and entrylo1 to cover the contiguous huge PTE
         * address space.
         */
        small_sequence = (HPAGE_SIZE >> 7) < 0x10000;

        /* We can clobber tmp.  It isn't used after this.*/
        if (!small_sequence)
                uasm_i_lui(p, tmp, HPAGE_SIZE >> (7 + 16));

        build_convert_pte_to_entrylo(p, pte);
        UASM_i_MTC0(p, pte, C0_ENTRYLO0); /* load it */
        /* convert to entrylo1 */
        if (small_sequence)
                UASM_i_ADDIU(p, pte, pte, HPAGE_SIZE >> 7);
        else
                UASM_i_ADDU(p, pte, pte, tmp);

        UASM_i_MTC0(p, pte, C0_ENTRYLO1); /* load it */
}

static void build_huge_handler_tail(u32 **p, struct uasm_reloc **r,
                                    struct uasm_label **l,
                                    unsigned int pte,
                                    unsigned int ptr,
                                    unsigned int flush)
{
#ifdef CONFIG_SMP
        UASM_i_SC(p, pte, 0, ptr);
        uasm_il_beqz(p, r, pte, label_tlb_huge_update);
        UASM_i_LW(p, pte, 0, ptr); /* Needed because SC killed our PTE */
#else
        UASM_i_SW(p, pte, 0, ptr);
#endif
        if (cpu_has_ftlb && flush) {
                BUG_ON(!cpu_has_tlbinv);

                UASM_i_MFC0(p, ptr, C0_ENTRYHI);
                uasm_i_ori(p, ptr, ptr, MIPS_ENTRYHI_EHINV);
                UASM_i_MTC0(p, ptr, C0_ENTRYHI);
                build_tlb_write_entry(p, l, r, tlb_indexed);

                uasm_i_xori(p, ptr, ptr, MIPS_ENTRYHI_EHINV);
                UASM_i_MTC0(p, ptr, C0_ENTRYHI);
                build_huge_update_entries(p, pte, ptr);
                build_huge_tlb_write_entry(p, l, r, pte, tlb_random, 0);

                return;
        }

        build_huge_update_entries(p, pte, ptr);
        build_huge_tlb_write_entry(p, l, r, pte, tlb_indexed, 0);
}
#endif /* CONFIG_MIPS_HUGE_TLB_SUPPORT */

#ifdef CONFIG_64BIT
/*
 * TMP and PTR are scratch.
 * TMP will be clobbered, PTR will hold the pmd entry.
 */
void build_get_pmde64(u32 **p, struct uasm_label **l, struct uasm_reloc **r,
                      unsigned int tmp, unsigned int ptr)
{
#ifndef CONFIG_MIPS_PGD_C0_CONTEXT
        long pgdc = (long)pgd_current;
#endif
        /*
         * The vmalloc handling is not in the hotpath.
         */
        uasm_i_dmfc0(p, tmp, C0_BADVADDR);

        if (check_for_high_segbits) {
                /*
                 * The kernel currently implicitely assumes that the
                 * MIPS SEGBITS parameter for the processor is
                 * (PGDIR_SHIFT+PGDIR_BITS) or less, and will never
                 * allocate virtual addresses outside the maximum
                 * range for SEGBITS = (PGDIR_SHIFT+PGDIR_BITS). But
                 * that doesn't prevent user code from accessing the
                 * higher xuseg addresses.  Here, we make sure that
                 * everything but the lower xuseg addresses goes down
                 * the module_alloc/vmalloc path.
                 */
                uasm_i_dsrl_safe(p, ptr, tmp, PGDIR_SHIFT + PGD_ORDER + PAGE_SHIFT - 3);
                uasm_il_bnez(p, r, ptr, label_vmalloc);
        } else {
                uasm_il_bltz(p, r, tmp, label_vmalloc);
        }
        /* No uasm_i_nop needed here, since the next insn doesn't touch TMP. */

        if (pgd_reg != -1) {
                /* pgd is in pgd_reg */
                if (cpu_has_ldpte)
                        UASM_i_MFC0(p, ptr, C0_PWBASE);
                else
                        UASM_i_MFC0(p, ptr, c0_kscratch(), pgd_reg);
        } else {
#if defined(CONFIG_MIPS_PGD_C0_CONTEXT)
                /*
                 * &pgd << 11 stored in CONTEXT [23..63].
                 */
                UASM_i_MFC0(p, ptr, C0_CONTEXT);

                /* Clear lower 23 bits of context. */
                uasm_i_dins(p, ptr, 0, 0, 23);

                /* 1 0  1 0 1  << 6  xkphys cached */
                uasm_i_ori(p, ptr, ptr, 0x540);
                uasm_i_drotr(p, ptr, ptr, 11);
#elif defined(CONFIG_SMP)
                UASM_i_CPUID_MFC0(p, ptr, SMP_CPUID_REG);
                uasm_i_dsrl_safe(p, ptr, ptr, SMP_CPUID_PTRSHIFT);
                UASM_i_LA_mostly(p, tmp, pgdc);
                uasm_i_daddu(p, ptr, ptr, tmp);
                uasm_i_dmfc0(p, tmp, C0_BADVADDR);
                uasm_i_ld(p, ptr, uasm_rel_lo(pgdc), ptr);
#else
                UASM_i_LA_mostly(p, ptr, pgdc);
                uasm_i_ld(p, ptr, uasm_rel_lo(pgdc), ptr);
#endif
        }

        uasm_l_vmalloc_done(l, *p);

        /* get pgd offset in bytes */
        uasm_i_dsrl_safe(p, tmp, tmp, PGDIR_SHIFT - 3);

        uasm_i_andi(p, tmp, tmp, (PTRS_PER_PGD - 1)<<3);
        uasm_i_daddu(p, ptr, ptr, tmp); /* add in pgd offset */
#ifndef __PAGETABLE_PUD_FOLDED
        uasm_i_dmfc0(p, tmp, C0_BADVADDR); /* get faulting address */
        uasm_i_ld(p, ptr, 0, ptr); /* get pud pointer */
        uasm_i_dsrl_safe(p, tmp, tmp, PUD_SHIFT - 3); /* get pud offset in bytes */
        uasm_i_andi(p, tmp, tmp, (PTRS_PER_PUD - 1) << 3);
        uasm_i_daddu(p, ptr, ptr, tmp); /* add in pud offset */
#endif
#ifndef __PAGETABLE_PMD_FOLDED
        uasm_i_dmfc0(p, tmp, C0_BADVADDR); /* get faulting address */
        uasm_i_ld(p, ptr, 0, ptr); /* get pmd pointer */
        uasm_i_dsrl_safe(p, tmp, tmp, PMD_SHIFT-3); /* get pmd offset in bytes */
        uasm_i_andi(p, tmp, tmp, (PTRS_PER_PMD - 1)<<3);
        uasm_i_daddu(p, ptr, ptr, tmp); /* add in pmd offset */
#endif
}
EXPORT_SYMBOL_GPL(build_get_pmde64);

/*
 * BVADDR is the faulting address, PTR is scratch.
 * PTR will hold the pgd for vmalloc.
 */
static void
build_get_pgd_vmalloc64(u32 **p, struct uasm_label **l, struct uasm_reloc **r,
                        unsigned int bvaddr, unsigned int ptr,
                        enum vmalloc64_mode mode)
{
        long swpd = (long)swapper_pg_dir;
        int single_insn_swpd;
        int did_vmalloc_branch = 0;

        single_insn_swpd = uasm_in_compat_space_p(swpd) && !uasm_rel_lo(swpd);

        uasm_l_vmalloc(l, *p);

        if (mode != not_refill && check_for_high_segbits) {
                if (single_insn_swpd) {
                        uasm_il_bltz(p, r, bvaddr, label_vmalloc_done);
                        uasm_i_lui(p, ptr, uasm_rel_hi(swpd));
                        did_vmalloc_branch = 1;
                        /* fall through */
                } else {
                        uasm_il_bgez(p, r, bvaddr, label_large_segbits_fault);
                }
        }
        if (!did_vmalloc_branch) {
                if (single_insn_swpd) {
                        uasm_il_b(p, r, label_vmalloc_done);
                        uasm_i_lui(p, ptr, uasm_rel_hi(swpd));
                } else {
                        UASM_i_LA_mostly(p, ptr, swpd);
                        uasm_il_b(p, r, label_vmalloc_done);
                        if (uasm_in_compat_space_p(swpd))
                                uasm_i_addiu(p, ptr, ptr, uasm_rel_lo(swpd));
                        else
                                uasm_i_daddiu(p, ptr, ptr, uasm_rel_lo(swpd));
                }
        }
        if (mode != not_refill && check_for_high_segbits) {
                uasm_l_large_segbits_fault(l, *p);

                if (mode == refill_scratch && scratch_reg >= 0)
                        uasm_i_ehb(p);

                /*
                 * We get here if we are an xsseg address, or if we are
                 * an xuseg address above (PGDIR_SHIFT+PGDIR_BITS) boundary.
                 *
                 * Ignoring xsseg (assume disabled so would generate
                 * (address errors?), the only remaining possibility
                 * is the upper xuseg addresses.  On processors with
                 * TLB_SEGBITS <= PGDIR_SHIFT+PGDIR_BITS, these
                 * addresses would have taken an address error. We try
                 * to mimic that here by taking a load/istream page
                 * fault.
                 */
                if (IS_ENABLED(CONFIG_CPU_LOONGSON3_WORKAROUNDS))
                        uasm_i_sync(p, 0);
                UASM_i_LA(p, ptr, (unsigned long)tlb_do_page_fault_0);
                uasm_i_jr(p, ptr);

                if (mode == refill_scratch) {
                        if (scratch_reg >= 0)
                                UASM_i_MFC0(p, 1, c0_kscratch(), scratch_reg);
                        else
                                UASM_i_LW(p, 1, scratchpad_offset(0), 0);
                } else {
                        uasm_i_nop(p);
                }
        }
}

#else /* !CONFIG_64BIT */

/*
 * TMP and PTR are scratch.
 * TMP will be clobbered, PTR will hold the pgd entry.
 */
void build_get_pgde32(u32 **p, unsigned int tmp, unsigned int ptr)
{
        if (pgd_reg != -1) {
                /* pgd is in pgd_reg */
                uasm_i_mfc0(p, ptr, c0_kscratch(), pgd_reg);
                uasm_i_mfc0(p, tmp, C0_BADVADDR); /* get faulting address */
        } else {
                long pgdc = (long)pgd_current;

                /* 32 bit SMP has smp_processor_id() stored in CONTEXT. */
#ifdef CONFIG_SMP
                uasm_i_mfc0(p, ptr, SMP_CPUID_REG);
                UASM_i_LA_mostly(p, tmp, pgdc);
                uasm_i_srl(p, ptr, ptr, SMP_CPUID_PTRSHIFT);
                uasm_i_addu(p, ptr, tmp, ptr);
#else
                UASM_i_LA_mostly(p, ptr, pgdc);
#endif
                uasm_i_mfc0(p, tmp, C0_BADVADDR); /* get faulting address */
                uasm_i_lw(p, ptr, uasm_rel_lo(pgdc), ptr);
        }
        uasm_i_srl(p, tmp, tmp, PGDIR_SHIFT); /* get pgd only bits */
        uasm_i_sll(p, tmp, tmp, PGD_T_LOG2);
        uasm_i_addu(p, ptr, ptr, tmp); /* add in pgd offset */
}
EXPORT_SYMBOL_GPL(build_get_pgde32);

#endif /* !CONFIG_64BIT */

static void build_adjust_context(u32 **p, unsigned int ctx)

{
        unsigned int shift = 4 - (PTE_T_LOG2 + 1) + PAGE_SHIFT - 12;
        unsigned int mask = (PTRS_PER_PTE / 2 - 1) << (PTE_T_LOG2 + 1);

        switch (current_cpu_type()) {
        case CPU_VR41XX:
        case CPU_VR4111:
        case CPU_VR4121:
        case CPU_VR4122:
        case CPU_VR4131:
        case CPU_VR4181:
        case CPU_VR4181A:
        case CPU_VR4133:
                shift += 2;
                break;

        default:
                break;
        }

        if (shift)
                UASM_i_SRL(p, ctx, ctx, shift);
        uasm_i_andi(p, ctx, ctx, mask);
}

void build_get_ptep(u32 **p, unsigned int tmp, unsigned int ptr)
{
        /*
         * Bug workaround for the Nevada. It seems as if under certain
         * circumstances the move from cp0_context might produce a
         * bogus result when the mfc0 instruction and its consumer are
         * in a different cacheline or a load instruction, probably any
         * memory reference, is between them.
         */
        switch (current_cpu_type()) {
        case CPU_NEVADA:
                UASM_i_LW(p, ptr, 0, ptr);
                GET_CONTEXT(p, tmp); /* get context reg */
                break;

        default:
                GET_CONTEXT(p, tmp); /* get context reg */
                UASM_i_LW(p, ptr, 0, ptr);
                break;
        }

        build_adjust_context(p, tmp);
        UASM_i_ADDU(p, ptr, ptr, tmp); /* add in offset */
}
EXPORT_SYMBOL_GPL(build_get_ptep);

void build_update_entries(u32 **p, unsigned int tmp, unsigned int ptep)
{
        int pte_off_even = 0;
        int pte_off_odd = sizeof(pte_t);

#if defined(CONFIG_CPU_MIPS32) && defined(CONFIG_PHYS_ADDR_T_64BIT)
        /* The low 32 bits of EntryLo is stored in pte_high */
        pte_off_even += offsetof(pte_t, pte_high);
        pte_off_odd += offsetof(pte_t, pte_high);
#endif

        if (IS_ENABLED(CONFIG_XPA)) {
                uasm_i_lw(p, tmp, pte_off_even, ptep); /* even pte */
                UASM_i_ROTR(p, tmp, tmp, ilog2(_PAGE_GLOBAL));
                UASM_i_MTC0(p, tmp, C0_ENTRYLO0);

                if (cpu_has_xpa && !mips_xpa_disabled) {
                        uasm_i_lw(p, tmp, 0, ptep);
                        uasm_i_ext(p, tmp, tmp, 0, 24);
                        uasm_i_mthc0(p, tmp, C0_ENTRYLO0);
                }

                uasm_i_lw(p, tmp, pte_off_odd, ptep); /* odd pte */
                UASM_i_ROTR(p, tmp, tmp, ilog2(_PAGE_GLOBAL));
                UASM_i_MTC0(p, tmp, C0_ENTRYLO1);

                if (cpu_has_xpa && !mips_xpa_disabled) {
                        uasm_i_lw(p, tmp, sizeof(pte_t), ptep);
                        uasm_i_ext(p, tmp, tmp, 0, 24);
                        uasm_i_mthc0(p, tmp, C0_ENTRYLO1);
                }
                return;
        }

        UASM_i_LW(p, tmp, pte_off_even, ptep); /* get even pte */
        UASM_i_LW(p, ptep, pte_off_odd, ptep); /* get odd pte */
        if (r45k_bvahwbug())
                build_tlb_probe_entry(p);
        build_convert_pte_to_entrylo(p, tmp);
        if (r4k_250MHZhwbug())
                UASM_i_MTC0(p, 0, C0_ENTRYLO0);
        UASM_i_MTC0(p, tmp, C0_ENTRYLO0); /* load it */
        build_convert_pte_to_entrylo(p, ptep);
        if (r45k_bvahwbug())
                uasm_i_mfc0(p, tmp, C0_INDEX);
        if (r4k_250MHZhwbug())
                UASM_i_MTC0(p, 0, C0_ENTRYLO1);
        UASM_i_MTC0(p, ptep, C0_ENTRYLO1); /* load it */
}
EXPORT_SYMBOL_GPL(build_update_entries);

struct mips_huge_tlb_info {
        int huge_pte;
        int restore_scratch;
        bool need_reload_pte;
};

static struct mips_huge_tlb_info
build_fast_tlb_refill_handler (u32 **p, struct uasm_label **l,
                               struct uasm_reloc **r, unsigned int tmp,
                               unsigned int ptr, int c0_scratch_reg)
{
        struct mips_huge_tlb_info rv;
        unsigned int even, odd;
        int vmalloc_branch_delay_filled = 0;
        const int scratch = 1; /* Our extra working register */

        rv.huge_pte = scratch;
        rv.restore_scratch = 0;
        rv.need_reload_pte = false;

        if (check_for_high_segbits) {
                UASM_i_MFC0(p, tmp, C0_BADVADDR);

                if (pgd_reg != -1)
                        UASM_i_MFC0(p, ptr, c0_kscratch(), pgd_reg);
                else
                        UASM_i_MFC0(p, ptr, C0_CONTEXT);

                if (c0_scratch_reg >= 0)
                        UASM_i_MTC0(p, scratch, c0_kscratch(), c0_scratch_reg);
                else
                        UASM_i_SW(p, scratch, scratchpad_offset(0), 0);

                uasm_i_dsrl_safe(p, scratch, tmp,
                                 PGDIR_SHIFT + PGD_ORDER + PAGE_SHIFT - 3);
                uasm_il_bnez(p, r, scratch, label_vmalloc);

                if (pgd_reg == -1) {
                        vmalloc_branch_delay_filled = 1;
                        /* Clear lower 23 bits of context. */
                        uasm_i_dins(p, ptr, 0, 0, 23);
                }
        } else {
                if (pgd_reg != -1)
                        UASM_i_MFC0(p, ptr, c0_kscratch(), pgd_reg);
                else
                        UASM_i_MFC0(p, ptr, C0_CONTEXT);

                UASM_i_MFC0(p, tmp, C0_BADVADDR);

                if (c0_scratch_reg >= 0)
                        UASM_i_MTC0(p, scratch, c0_kscratch(), c0_scratch_reg);
                else
                        UASM_i_SW(p, scratch, scratchpad_offset(0), 0);

                if (pgd_reg == -1)
                        /* Clear lower 23 bits of context. */
                        uasm_i_dins(p, ptr, 0, 0, 23);

                uasm_il_bltz(p, r, tmp, label_vmalloc);
        }

        if (pgd_reg == -1) {
                vmalloc_branch_delay_filled = 1;
                /* 1 0  1 0 1  << 6  xkphys cached */
                uasm_i_ori(p, ptr, ptr, 0x540);
                uasm_i_drotr(p, ptr, ptr, 11);
        }

#ifdef __PAGETABLE_PMD_FOLDED
#define LOC_PTEP scratch
#else
#define LOC_PTEP ptr
#endif

        if (!vmalloc_branch_delay_filled)
                /* get pgd offset in bytes */
                uasm_i_dsrl_safe(p, scratch, tmp, PGDIR_SHIFT - 3);

        uasm_l_vmalloc_done(l, *p);

        /*
         *                         tmp          ptr
         * fall-through case =   badvaddr  *pgd_current
         * vmalloc case      =   badvaddr  swapper_pg_dir
         */

        if (vmalloc_branch_delay_filled)
                /* get pgd offset in bytes */
                uasm_i_dsrl_safe(p, scratch, tmp, PGDIR_SHIFT - 3);

#ifdef __PAGETABLE_PMD_FOLDED
        GET_CONTEXT(p, tmp); /* get context reg */
#endif
        uasm_i_andi(p, scratch, scratch, (PTRS_PER_PGD - 1) << 3);

        if (use_lwx_insns()) {
                UASM_i_LWX(p, LOC_PTEP, scratch, ptr);
        } else {
                uasm_i_daddu(p, ptr, ptr, scratch); /* add in pgd offset */
                uasm_i_ld(p, LOC_PTEP, 0, ptr); /* get pmd pointer */
        }

#ifndef __PAGETABLE_PUD_FOLDED
        /* get pud offset in bytes */
        uasm_i_dsrl_safe(p, scratch, tmp, PUD_SHIFT - 3);
        uasm_i_andi(p, scratch, scratch, (PTRS_PER_PUD - 1) << 3);

        if (use_lwx_insns()) {
                UASM_i_LWX(p, ptr, scratch, ptr);
        } else {
                uasm_i_daddu(p, ptr, ptr, scratch); /* add in pmd offset */
                UASM_i_LW(p, ptr, 0, ptr);
        }
        /* ptr contains a pointer to PMD entry */
        /* tmp contains the address */
#endif

#ifndef __PAGETABLE_PMD_FOLDED
        /* get pmd offset in bytes */
        uasm_i_dsrl_safe(p, scratch, tmp, PMD_SHIFT - 3);
        uasm_i_andi(p, scratch, scratch, (PTRS_PER_PMD - 1) << 3);
        GET_CONTEXT(p, tmp); /* get context reg */

        if (use_lwx_insns()) {
                UASM_i_LWX(p, scratch, scratch, ptr);
        } else {
                uasm_i_daddu(p, ptr, ptr, scratch); /* add in pmd offset */
                UASM_i_LW(p, scratch, 0, ptr);
        }
#endif
        /* Adjust the context during the load latency. */
        build_adjust_context(p, tmp);

#ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
        uasm_il_bbit1(p, r, scratch, ilog2(_PAGE_HUGE), label_tlb_huge_update);
        /*
         * The in the LWX case we don't want to do the load in the
         * delay slot.  It cannot issue in the same cycle and may be
         * speculative and unneeded.
         */
        if (use_lwx_insns())
                uasm_i_nop(p);
#endif /* CONFIG_MIPS_HUGE_TLB_SUPPORT */


        /* build_update_entries */
        if (use_lwx_insns()) {
                even = ptr;
                odd = tmp;
                UASM_i_LWX(p, even, scratch, tmp);
                UASM_i_ADDIU(p, tmp, tmp, sizeof(pte_t));
                UASM_i_LWX(p, odd, scratch, tmp);
        } else {
                UASM_i_ADDU(p, ptr, scratch, tmp); /* add in offset */
                even = tmp;
                odd = ptr;
                UASM_i_LW(p, even, 0, ptr); /* get even pte */
                UASM_i_LW(p, odd, sizeof(pte_t), ptr); /* get odd pte */
        }
        if (cpu_has_rixi) {
                uasm_i_drotr(p, even, even, ilog2(_PAGE_GLOBAL));
                UASM_i_MTC0(p, even, C0_ENTRYLO0); /* load it */
                uasm_i_drotr(p, odd, odd, ilog2(_PAGE_GLOBAL));
        } else {
                uasm_i_dsrl_safe(p, even, even, ilog2(_PAGE_GLOBAL));
                UASM_i_MTC0(p, even, C0_ENTRYLO0); /* load it */
                uasm_i_dsrl_safe(p, odd, odd, ilog2(_PAGE_GLOBAL));
        }
        UASM_i_MTC0(p, odd, C0_ENTRYLO1); /* load it */

        if (c0_scratch_reg >= 0) {
                uasm_i_ehb(p);
                UASM_i_MFC0(p, scratch, c0_kscratch(), c0_scratch_reg);
                build_tlb_write_entry(p, l, r, tlb_random);
                uasm_l_leave(l, *p);
                rv.restore_scratch = 1;
        } else if (PAGE_SHIFT == 14 || PAGE_SHIFT == 13)  {
                build_tlb_write_entry(p, l, r, tlb_random);
                uasm_l_leave(l, *p);
                UASM_i_LW(p, scratch, scratchpad_offset(0), 0);
        } else {
                UASM_i_LW(p, scratch, scratchpad_offset(0), 0);
                build_tlb_write_entry(p, l, r, tlb_random);
                uasm_l_leave(l, *p);
                rv.restore_scratch = 1;
        }

        uasm_i_eret(p); /* return from trap */

        return rv;
}

/*
 * For a 64-bit kernel, we are using the 64-bit XTLB refill exception
 * because EXL == 0.  If we wrap, we can also use the 32 instruction
 * slots before the XTLB refill exception handler which belong to the
 * unused TLB refill exception.
 */
#define MIPS64_REFILL_INSNS 32

static void build_r4000_tlb_refill_handler(void)
{
        u32 *p = tlb_handler;
        struct uasm_label *l = labels;
        struct uasm_reloc *r = relocs;
        u32 *f;
        unsigned int final_len;
        struct mips_huge_tlb_info htlb_info __maybe_unused;
        enum vmalloc64_mode vmalloc_mode __maybe_unused;

        memset(tlb_handler, 0, sizeof(tlb_handler));
        memset(labels, 0, sizeof(labels));
        memset(relocs, 0, sizeof(relocs));
        memset(final_handler, 0, sizeof(final_handler));

        if (IS_ENABLED(CONFIG_64BIT) && (scratch_reg >= 0 || scratchpad_available()) && use_bbit_insns()) {
                htlb_info = build_fast_tlb_refill_handler(&p, &l, &r, K0, K1,
                                                          scratch_reg);
                vmalloc_mode = refill_scratch;
        } else {
                htlb_info.huge_pte = K0;
                htlb_info.restore_scratch = 0;
                htlb_info.need_reload_pte = true;
                vmalloc_mode = refill_noscratch;
                /*
                 * create the plain linear handler
                 */
                if (bcm1250_m3_war()) {
                        unsigned int segbits = 44;

                        uasm_i_dmfc0(&p, K0, C0_BADVADDR);
                        uasm_i_dmfc0(&p, K1, C0_ENTRYHI);
                        uasm_i_xor(&p, K0, K0, K1);
                        uasm_i_dsrl_safe(&p, K1, K0, 62);
                        uasm_i_dsrl_safe(&p, K0, K0, 12 + 1);
                        uasm_i_dsll_safe(&p, K0, K0, 64 + 12 + 1 - segbits);
                        uasm_i_or(&p, K0, K0, K1);
                        uasm_il_bnez(&p, &r, K0, label_leave);
                        /* No need for uasm_i_nop */
                }

#ifdef CONFIG_64BIT
                build_get_pmde64(&p, &l, &r, K0, K1); /* get pmd in K1 */
#else
                build_get_pgde32(&p, K0, K1); /* get pgd in K1 */
#endif

#ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
                build_is_huge_pte(&p, &r, K0, K1, label_tlb_huge_update);
#endif

                build_get_ptep(&p, K0, K1);
                build_update_entries(&p, K0, K1);
                build_tlb_write_entry(&p, &l, &r, tlb_random);
                uasm_l_leave(&l, p);
                uasm_i_eret(&p); /* return from trap */
        }
#ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
        uasm_l_tlb_huge_update(&l, p);
        if (htlb_info.need_reload_pte)
                UASM_i_LW(&p, htlb_info.huge_pte, 0, K1);
        build_huge_update_entries(&p, htlb_info.huge_pte, K1);
        build_huge_tlb_write_entry(&p, &l, &r, K0, tlb_random,
                                   htlb_info.restore_scratch);
#endif

#ifdef CONFIG_64BIT
        build_get_pgd_vmalloc64(&p, &l, &r, K0, K1, vmalloc_mode);
#endif

        /*
         * Overflow check: For the 64bit handler, we need at least one
         * free instruction slot for the wrap-around branch. In worst
         * case, if the intended insertion point is a delay slot, we
         * need three, with the second nop'ed and the third being
         * unused.
         */
        switch (boot_cpu_type()) {
        default:
                if (sizeof(long) == 4) {
        case CPU_LOONGSON2EF:
                /* Loongson2 ebase is different than r4k, we have more space */
                        if ((p - tlb_handler) > 64)
                                panic("TLB refill handler space exceeded");
                        /*
                         * Now fold the handler in the TLB refill handler space.
                         */
                        f = final_handler;
                        /* Simplest case, just copy the handler. */
                        uasm_copy_handler(relocs, labels, tlb_handler, p, f);
                        final_len = p - tlb_handler;
                        break;
                } else {
                        if (((p - tlb_handler) > (MIPS64_REFILL_INSNS * 2) - 1)
                            || (((p - tlb_handler) > (MIPS64_REFILL_INSNS * 2) - 3)
                                && uasm_insn_has_bdelay(relocs,
                                                        tlb_handler + MIPS64_REFILL_INSNS - 3)))
                                panic("TLB refill handler space exceeded");
                        /*
                         * Now fold the handler in the TLB refill handler space.
                         */
                        f = final_handler + MIPS64_REFILL_INSNS;
                        if ((p - tlb_handler) <= MIPS64_REFILL_INSNS) {
                                /* Just copy the handler. */
                                uasm_copy_handler(relocs, labels, tlb_handler, p, f);
                                final_len = p - tlb_handler;
                        } else {
#ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
                                const enum label_id ls = label_tlb_huge_update;
#else
                                const enum label_id ls = label_vmalloc;
#endif
                                u32 *split;
                                int ov = 0;
                                int i;

                                for (i = 0; i < ARRAY_SIZE(labels) && labels[i].lab != ls; i++)
                                        ;
                                BUG_ON(i == ARRAY_SIZE(labels));
                                split = labels[i].addr;

                                /*
                                 * See if we have overflown one way or the other.
                                 */
                                if (split > tlb_handler + MIPS64_REFILL_INSNS ||
                                    split < p - MIPS64_REFILL_INSNS)
                                        ov = 1;

                                if (ov) {
                                        /*
                                         * Split two instructions before the end.  One
                                         * for the branch and one for the instruction
                                         * in the delay slot.
                                         */
                                        split = tlb_handler + MIPS64_REFILL_INSNS - 2;

                                        /*
                                         * If the branch would fall in a delay slot,
                                         * we must back up an additional instruction
                                         * so that it is no longer in a delay slot.
                                         */
                                        if (uasm_insn_has_bdelay(relocs, split - 1))
                                                split--;
                                }
                                /* Copy first part of the handler. */
                                uasm_copy_handler(relocs, labels, tlb_handler, split, f);
                                f += split - tlb_handler;

                                if (ov) {
                                        /* Insert branch. */
                                        uasm_l_split(&l, final_handler);
                                        uasm_il_b(&f, &r, label_split);
                                        if (uasm_insn_has_bdelay(relocs, split))
                                                uasm_i_nop(&f);
                                        else {
                                                uasm_copy_handler(relocs, labels,
                                                                  split, split + 1, f);
                                                uasm_move_labels(labels, f, f + 1, -1);
                                                f++;
                                                split++;
                                        }
                                }

                                /* Copy the rest of the handler. */
                                uasm_copy_handler(relocs, labels, split, p, final_handler);
                                final_len = (f - (final_handler + MIPS64_REFILL_INSNS)) +
                                            (p - split);
                        }
                }
                break;
        }

        uasm_resolve_relocs(relocs, labels);
        pr_debug("Wrote TLB refill handler (%u instructions).\n",
                 final_len);

        memcpy((void *)ebase, final_handler, 0x100);
        local_flush_icache_range(ebase, ebase + 0x100);
        dump_handler("r4000_tlb_refill", (u32 *)ebase, (u32 *)(ebase + 0x100));
}

static void setup_pw(void)
{
        unsigned int pwctl;
        unsigned long pgd_i, pgd_w;
#ifndef __PAGETABLE_PMD_FOLDED
        unsigned long pmd_i, pmd_w;
#endif
        unsigned long pt_i, pt_w;
        unsigned long pte_i, pte_w;
#ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
        unsigned long psn;

        psn = ilog2(_PAGE_HUGE);     /* bit used to indicate huge page */
#endif
        pgd_i = PGDIR_SHIFT;  /* 1st level PGD */
#ifndef __PAGETABLE_PMD_FOLDED
        pgd_w = PGDIR_SHIFT - PMD_SHIFT + PGD_ORDER;

        pmd_i = PMD_SHIFT;    /* 2nd level PMD */
        pmd_w = PMD_SHIFT - PAGE_SHIFT;
#else
        pgd_w = PGDIR_SHIFT - PAGE_SHIFT + PGD_ORDER;
#endif

        pt_i  = PAGE_SHIFT;    /* 3rd level PTE */
        pt_w  = PAGE_SHIFT - 3;

        pte_i = ilog2(_PAGE_GLOBAL);
        pte_w = 0;
        pwctl = 1 << 30; /* Set PWDirExt */

#ifndef __PAGETABLE_PMD_FOLDED
        write_c0_pwfield(pgd_i << 24 | pmd_i << 12 | pt_i << 6 | pte_i);
        write_c0_pwsize(1 << 30 | pgd_w << 24 | pmd_w << 12 | pt_w << 6 | pte_w);
#else
        write_c0_pwfield(pgd_i << 24 | pt_i << 6 | pte_i);
        write_c0_pwsize(1 << 30 | pgd_w << 24 | pt_w << 6 | pte_w);
#endif

#ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
        pwctl |= (1 << 6 | psn);
#endif
        write_c0_pwctl(pwctl);
        write_c0_kpgd((long)swapper_pg_dir);
        kscratch_used_mask |= (1 << 7); /* KScratch6 is used for KPGD */
}

static void build_loongson3_tlb_refill_handler(void)
{
        u32 *p = tlb_handler;
        struct uasm_label *l = labels;
        struct uasm_reloc *r = relocs;

        memset(labels, 0, sizeof(labels));
        memset(relocs, 0, sizeof(relocs));
        memset(tlb_handler, 0, sizeof(tlb_handler));

        if (check_for_high_segbits) {
                uasm_i_dmfc0(&p, K0, C0_BADVADDR);
                uasm_i_dsrl_safe(&p, K1, K0, PGDIR_SHIFT + PGD_ORDER + PAGE_SHIFT - 3);
                uasm_il_beqz(&p, &r, K1, label_vmalloc);
                uasm_i_nop(&p);

                uasm_il_bgez(&p, &r, K0, label_large_segbits_fault);
                uasm_i_nop(&p);
                uasm_l_vmalloc(&l, p);
        }

        uasm_i_dmfc0(&p, K1, C0_PGD);

        uasm_i_lddir(&p, K0, K1, 3);  /* global page dir */
#ifndef __PAGETABLE_PMD_FOLDED
        uasm_i_lddir(&p, K1, K0, 1);  /* middle page dir */
#endif
        uasm_i_ldpte(&p, K1, 0);      /* even */
        uasm_i_ldpte(&p, K1, 1);      /* odd */
        uasm_i_tlbwr(&p);

        /* restore page mask */
        if (PM_DEFAULT_MASK >> 16) {
                uasm_i_lui(&p, K0, PM_DEFAULT_MASK >> 16);
                uasm_i_ori(&p, K0, K0, PM_DEFAULT_MASK & 0xffff);
                uasm_i_mtc0(&p, K0, C0_PAGEMASK);
        } else if (PM_DEFAULT_MASK) {
                uasm_i_ori(&p, K0, 0, PM_DEFAULT_MASK);
                uasm_i_mtc0(&p, K0, C0_PAGEMASK);
        } else {
                uasm_i_mtc0(&p, 0, C0_PAGEMASK);
        }

        uasm_i_eret(&p);

        if (check_for_high_segbits) {
                uasm_l_large_segbits_fault(&l, p);
                UASM_i_LA(&p, K1, (unsigned long)tlb_do_page_fault_0);
                uasm_i_jr(&p, K1);
                uasm_i_nop(&p);
        }

        uasm_resolve_relocs(relocs, labels);
        memcpy((void *)(ebase + 0x80), tlb_handler, 0x80);
        local_flush_icache_range(ebase + 0x80, ebase + 0x100);
        dump_handler("loongson3_tlb_refill",
                     (u32 *)(ebase + 0x80), (u32 *)(ebase + 0x100));
}

static void build_setup_pgd(void)
{
        const int a0 = 4;
        const int __maybe_unused a1 = 5;
        const int __maybe_unused a2 = 6;
        u32 *p = (u32 *)msk_isa16_mode((ulong)tlbmiss_handler_setup_pgd);
#ifndef CONFIG_MIPS_PGD_C0_CONTEXT
        long pgdc = (long)pgd_current;
#endif

        memset(p, 0, tlbmiss_handler_setup_pgd_end - (char *)p);
        memset(labels, 0, sizeof(labels));
        memset(relocs, 0, sizeof(relocs));
        pgd_reg = allocate_kscratch();
#ifdef CONFIG_MIPS_PGD_C0_CONTEXT
        if (pgd_reg == -1) {
                struct uasm_label *l = labels;
                struct uasm_reloc *r = relocs;

                /* PGD << 11 in c0_Context */
                /*
                 * If it is a ckseg0 address, convert to a physical
                 * address.  Shifting right by 29 and adding 4 will
                 * result in zero for these addresses.
                 *
                 */
                UASM_i_SRA(&p, a1, a0, 29);
                UASM_i_ADDIU(&p, a1, a1, 4);
                uasm_il_bnez(&p, &r, a1, label_tlbl_goaround1);
                uasm_i_nop(&p);
                uasm_i_dinsm(&p, a0, 0, 29, 64 - 29);
                uasm_l_tlbl_goaround1(&l, p);
                UASM_i_SLL(&p, a0, a0, 11);
                UASM_i_MTC0(&p, a0, C0_CONTEXT);
                uasm_i_jr(&p, 31);
                uasm_i_ehb(&p);
        } else {
                /* PGD in c0_KScratch */
                if (cpu_has_ldpte)
                        UASM_i_MTC0(&p, a0, C0_PWBASE);
                else
                        UASM_i_MTC0(&p, a0, c0_kscratch(), pgd_reg);
                uasm_i_jr(&p, 31);
                uasm_i_ehb(&p);
        }
#else
#ifdef CONFIG_SMP
        /* Save PGD to pgd_current[smp_processor_id()] */
        UASM_i_CPUID_MFC0(&p, a1, SMP_CPUID_REG);
        UASM_i_SRL_SAFE(&p, a1, a1, SMP_CPUID_PTRSHIFT);
        UASM_i_LA_mostly(&p, a2, pgdc);
        UASM_i_ADDU(&p, a2, a2, a1);
        UASM_i_SW(&p, a0, uasm_rel_lo(pgdc), a2);
#else
        UASM_i_LA_mostly(&p, a2, pgdc);
        UASM_i_SW(&p, a0, uasm_rel_lo(pgdc), a2);
#endif /* SMP */

        /* if pgd_reg is allocated, save PGD also to scratch register */
        if (pgd_reg != -1) {
                UASM_i_MTC0(&p, a0, c0_kscratch(), pgd_reg);
                uasm_i_jr(&p, 31);
                uasm_i_ehb(&p);
        } else {
                uasm_i_jr(&p, 31);
                uasm_i_nop(&p);
        }
#endif
        if (p >= (u32 *)tlbmiss_handler_setup_pgd_end)
                panic("tlbmiss_handler_setup_pgd space exceeded");

        uasm_resolve_relocs(relocs, labels);
        pr_debug("Wrote tlbmiss_handler_setup_pgd (%u instructions).\n",
                 (unsigned int)(p - (u32 *)tlbmiss_handler_setup_pgd));

        dump_handler("tlbmiss_handler", tlbmiss_handler_setup_pgd,
                                        tlbmiss_handler_setup_pgd_end);
}

static void
iPTE_LW(u32 **p, unsigned int pte, unsigned int ptr)
{
#ifdef CONFIG_SMP
        if (IS_ENABLED(CONFIG_CPU_LOONGSON3_WORKAROUNDS))
                uasm_i_sync(p, 0);
# ifdef CONFIG_PHYS_ADDR_T_64BIT
        if (cpu_has_64bits)
                uasm_i_lld(p, pte, 0, ptr);
        else
# endif
                UASM_i_LL(p, pte, 0, ptr);
#else
# ifdef CONFIG_PHYS_ADDR_T_64BIT
        if (cpu_has_64bits)
                uasm_i_ld(p, pte, 0, ptr);
        else
# endif
                UASM_i_LW(p, pte, 0, ptr);
#endif
}

static void
iPTE_SW(u32 **p, struct uasm_reloc **r, unsigned int pte, unsigned int ptr,
        unsigned int mode, unsigned int scratch)
{
        unsigned int hwmode = mode & (_PAGE_VALID | _PAGE_DIRTY);
        unsigned int swmode = mode & ~hwmode;

        if (IS_ENABLED(CONFIG_XPA) && !cpu_has_64bits) {
                uasm_i_lui(p, scratch, swmode >> 16);
                uasm_i_or(p, pte, pte, scratch);
                BUG_ON(swmode & 0xffff);
        } else {
                uasm_i_ori(p, pte, pte, mode);
        }

#ifdef CONFIG_SMP
# ifdef CONFIG_PHYS_ADDR_T_64BIT
        if (cpu_has_64bits)
                uasm_i_scd(p, pte, 0, ptr);
        else
# endif
                UASM_i_SC(p, pte, 0, ptr);

        if (r10000_llsc_war())
                uasm_il_beqzl(p, r, pte, label_smp_pgtable_change);
        else
                uasm_il_beqz(p, r, pte, label_smp_pgtable_change);

# ifdef CONFIG_PHYS_ADDR_T_64BIT
        if (!cpu_has_64bits) {
                /* no uasm_i_nop needed */
                uasm_i_ll(p, pte, sizeof(pte_t) / 2, ptr);
                uasm_i_ori(p, pte, pte, hwmode);
                BUG_ON(hwmode & ~0xffff);
                uasm_i_sc(p, pte, sizeof(pte_t) / 2, ptr);
                uasm_il_beqz(p, r, pte, label_smp_pgtable_change);
                /* no uasm_i_nop needed */
                uasm_i_lw(p, pte, 0, ptr);
        } else
                uasm_i_nop(p);
# else
        uasm_i_nop(p);
# endif
#else
# ifdef CONFIG_PHYS_ADDR_T_64BIT
        if (cpu_has_64bits)
                uasm_i_sd(p, pte, 0, ptr);
        else
# endif
                UASM_i_SW(p, pte, 0, ptr);

# ifdef CONFIG_PHYS_ADDR_T_64BIT
        if (!cpu_has_64bits) {
                uasm_i_lw(p, pte, sizeof(pte_t) / 2, ptr);
                uasm_i_ori(p, pte, pte, hwmode);
                BUG_ON(hwmode & ~0xffff);
                uasm_i_sw(p, pte, sizeof(pte_t) / 2, ptr);
                uasm_i_lw(p, pte, 0, ptr);
        }
# endif
#endif
}

/*
 * Check if PTE is present, if not then jump to LABEL. PTR points to
 * the page table where this PTE is located, PTE will be re-loaded
 * with it's original value.
 */
static void
build_pte_present(u32 **p, struct uasm_reloc **r,
                  int pte, int ptr, int scratch, enum label_id lid)
{
        int t = scratch >= 0 ? scratch : pte;
        int cur = pte;

        if (cpu_has_rixi) {
                if (use_bbit_insns()) {
                        uasm_il_bbit0(p, r, pte, ilog2(_PAGE_PRESENT), lid);
                        uasm_i_nop(p);
                } else {
                        if (_PAGE_PRESENT_SHIFT) {
                                uasm_i_srl(p, t, cur, _PAGE_PRESENT_SHIFT);
                                cur = t;
                        }
                        uasm_i_andi(p, t, cur, 1);
                        uasm_il_beqz(p, r, t, lid);
                        if (pte == t)
                                /* You lose the SMP race :-(*/
                                iPTE_LW(p, pte, ptr);
                }
        } else {
                if (_PAGE_PRESENT_SHIFT) {
                        uasm_i_srl(p, t, cur, _PAGE_PRESENT_SHIFT);
                        cur = t;
                }
                uasm_i_andi(p, t, cur,
                        (_PAGE_PRESENT | _PAGE_NO_READ) >> _PAGE_PRESENT_SHIFT);
                uasm_i_xori(p, t, t, _PAGE_PRESENT >> _PAGE_PRESENT_SHIFT);
                uasm_il_bnez(p, r, t, lid);
                if (pte == t)
                        /* You lose the SMP race :-(*/
                        iPTE_LW(p, pte, ptr);
        }
}

/* Make PTE valid, store result in PTR. */
static void
build_make_valid(u32 **p, struct uasm_reloc **r, unsigned int pte,
                 unsigned int ptr, unsigned int scratch)
{
        unsigned int mode = _PAGE_VALID | _PAGE_ACCESSED;

        iPTE_SW(p, r, pte, ptr, mode, scratch);
}

/*
 * Check if PTE can be written to, if not branch to LABEL. Regardless
 * restore PTE with value from PTR when done.
 */
static void
build_pte_writable(u32 **p, struct uasm_reloc **r,
                   unsigned int pte, unsigned int ptr, int scratch,
                   enum label_id lid)
{
        int t = scratch >= 0 ? scratch : pte;
        int cur = pte;

        if (_PAGE_PRESENT_SHIFT) {
                uasm_i_srl(p, t, cur, _PAGE_PRESENT_SHIFT);
                cur = t;
        }
        uasm_i_andi(p, t, cur,
                    (_PAGE_PRESENT | _PAGE_WRITE) >> _PAGE_PRESENT_SHIFT);
        uasm_i_xori(p, t, t,
                    (_PAGE_PRESENT | _PAGE_WRITE) >> _PAGE_PRESENT_SHIFT);
        uasm_il_bnez(p, r, t, lid);
        if (pte == t)
                /* You lose the SMP race :-(*/
                iPTE_LW(p, pte, ptr);
        else
                uasm_i_nop(p);
}

/* Make PTE writable, update software status bits as well, then store
 * at PTR.
 */
static void
build_make_write(u32 **p, struct uasm_reloc **r, unsigned int pte,
                 unsigned int ptr, unsigned int scratch)
{
        unsigned int mode = (_PAGE_ACCESSED | _PAGE_MODIFIED | _PAGE_VALID
                             | _PAGE_DIRTY);

        iPTE_SW(p, r, pte, ptr, mode, scratch);
}

/*
 * Check if PTE can be modified, if not branch to LABEL. Regardless
 * restore PTE with value from PTR when done.
 */
static void
build_pte_modifiable(u32 **p, struct uasm_reloc **r,
                     unsigned int pte, unsigned int ptr, int scratch,
                     enum label_id lid)
{
        if (use_bbit_insns()) {
                uasm_il_bbit0(p, r, pte, ilog2(_PAGE_WRITE), lid);
                uasm_i_nop(p);
        } else {
                int t = scratch >= 0 ? scratch : pte;
                uasm_i_srl(p, t, pte, _PAGE_WRITE_SHIFT);
                uasm_i_andi(p, t, t, 1);
                uasm_il_beqz(p, r, t, lid);
                if (pte == t)
                        /* You lose the SMP race :-(*/
                        iPTE_LW(p, pte, ptr);
        }
}

#ifndef CONFIG_MIPS_PGD_C0_CONTEXT


/*
 * R3000 style TLB load/store/modify handlers.
 */

/*
 * This places the pte into ENTRYLO0 and writes it with tlbwi.
 * Then it returns.
 */
static void
build_r3000_pte_reload_tlbwi(u32 **p, unsigned int pte, unsigned int tmp)
{
        uasm_i_mtc0(p, pte, C0_ENTRYLO0); /* cp0 delay */
        uasm_i_mfc0(p, tmp, C0_EPC); /* cp0 delay */
        uasm_i_tlbwi(p);
        uasm_i_jr(p, tmp);
        uasm_i_rfe(p); /* branch delay */
}

/*
 * This places the pte into ENTRYLO0 and writes it with tlbwi
 * or tlbwr as appropriate.  This is because the index register
 * may have the probe fail bit set as a result of a trap on a
 * kseg2 access, i.e. without refill.  Then it returns.
 */
static void
build_r3000_tlb_reload_write(u32 **p, struct uasm_label **l,
                             struct uasm_reloc **r, unsigned int pte,
                             unsigned int tmp)
{
        uasm_i_mfc0(p, tmp, C0_INDEX);
        uasm_i_mtc0(p, pte, C0_ENTRYLO0); /* cp0 delay */
        uasm_il_bltz(p, r, tmp, label_r3000_write_probe_fail); /* cp0 delay */
        uasm_i_mfc0(p, tmp, C0_EPC); /* branch delay */
        uasm_i_tlbwi(p); /* cp0 delay */
        uasm_i_jr(p, tmp);
        uasm_i_rfe(p); /* branch delay */
        uasm_l_r3000_write_probe_fail(l, *p);
        uasm_i_tlbwr(p); /* cp0 delay */
        uasm_i_jr(p, tmp);
        uasm_i_rfe(p); /* branch delay */
}

static void
build_r3000_tlbchange_handler_head(u32 **p, unsigned int pte,
                                   unsigned int ptr)
{
        long pgdc = (long)pgd_current;

        uasm_i_mfc0(p, pte, C0_BADVADDR);
        uasm_i_lui(p, ptr, uasm_rel_hi(pgdc)); /* cp0 delay */
        uasm_i_lw(p, ptr, uasm_rel_lo(pgdc), ptr);
        uasm_i_srl(p, pte, pte, 22); /* load delay */
        uasm_i_sll(p, pte, pte, 2);
        uasm_i_addu(p, ptr, ptr, pte);
        uasm_i_mfc0(p, pte, C0_CONTEXT);
        uasm_i_lw(p, ptr, 0, ptr); /* cp0 delay */
        uasm_i_andi(p, pte, pte, 0xffc); /* load delay */
        uasm_i_addu(p, ptr, ptr, pte);
        uasm_i_lw(p, pte, 0, ptr);
        uasm_i_tlbp(p); /* load delay */
}

static void build_r3000_tlb_load_handler(void)
{
        u32 *p = (u32 *)handle_tlbl;
        struct uasm_label *l = labels;
        struct uasm_reloc *r = relocs;

        memset(p, 0, handle_tlbl_end - (char *)p);
        memset(labels, 0, sizeof(labels));
        memset(relocs, 0, sizeof(relocs));

        build_r3000_tlbchange_handler_head(&p, K0, K1);
        build_pte_present(&p, &r, K0, K1, -1, label_nopage_tlbl);
        uasm_i_nop(&p); /* load delay */
        build_make_valid(&p, &r, K0, K1, -1);
        build_r3000_tlb_reload_write(&p, &l, &r, K0, K1);

        uasm_l_nopage_tlbl(&l, p);
        uasm_i_j(&p, (unsigned long)tlb_do_page_fault_0 & 0x0fffffff);
        uasm_i_nop(&p);

        if (p >= (u32 *)handle_tlbl_end)
                panic("TLB load handler fastpath space exceeded");

        uasm_resolve_relocs(relocs, labels);
        pr_debug("Wrote TLB load handler fastpath (%u instructions).\n",
                 (unsigned int)(p - (u32 *)handle_tlbl));

        dump_handler("r3000_tlb_load", handle_tlbl, handle_tlbl_end);
}

static void build_r3000_tlb_store_handler(void)
{
        u32 *p = (u32 *)handle_tlbs;
        struct uasm_label *l = labels;
        struct uasm_reloc *r = relocs;

        memset(p, 0, handle_tlbs_end - (char *)p);
        memset(labels, 0, sizeof(labels));
        memset(relocs, 0, sizeof(relocs));

        build_r3000_tlbchange_handler_head(&p, K0, K1);
        build_pte_writable(&p, &r, K0, K1, -1, label_nopage_tlbs);
        uasm_i_nop(&p); /* load delay */
        build_make_write(&p, &r, K0, K1, -1);
        build_r3000_tlb_reload_write(&p, &l, &r, K0, K1);

        uasm_l_nopage_tlbs(&l, p);
        uasm_i_j(&p, (unsigned long)tlb_do_page_fault_1 & 0x0fffffff);
        uasm_i_nop(&p);

        if (p >= (u32 *)handle_tlbs_end)
                panic("TLB store handler fastpath space exceeded");

        uasm_resolve_relocs(relocs, labels);
        pr_debug("Wrote TLB store handler fastpath (%u instructions).\n",
                 (unsigned int)(p - (u32 *)handle_tlbs));

        dump_handler("r3000_tlb_store", handle_tlbs, handle_tlbs_end);
}

static void build_r3000_tlb_modify_handler(void)
{
        u32 *p = (u32 *)handle_tlbm;
        struct uasm_label *l = labels;
        struct uasm_reloc *r = relocs;

        memset(p, 0, handle_tlbm_end - (char *)p);
        memset(labels, 0, sizeof(labels));
        memset(relocs, 0, sizeof(relocs));

        build_r3000_tlbchange_handler_head(&p, K0, K1);
        build_pte_modifiable(&p, &r, K0, K1,  -1, label_nopage_tlbm);
        uasm_i_nop(&p); /* load delay */
        build_make_write(&p, &r, K0, K1, -1);
        build_r3000_pte_reload_tlbwi(&p, K0, K1);

        uasm_l_nopage_tlbm(&l, p);
        uasm_i_j(&p, (unsigned long)tlb_do_page_fault_1 & 0x0fffffff);
        uasm_i_nop(&p);

        if (p >= (u32 *)handle_tlbm_end)
                panic("TLB modify handler fastpath space exceeded");

        uasm_resolve_relocs(relocs, labels);
        pr_debug("Wrote TLB modify handler fastpath (%u instructions).\n",
                 (unsigned int)(p - (u32 *)handle_tlbm));

        dump_handler("r3000_tlb_modify", handle_tlbm, handle_tlbm_end);
}
#endif /* CONFIG_MIPS_PGD_C0_CONTEXT */

static bool cpu_has_tlbex_tlbp_race(void)
{
        /*
         * When a Hardware Table Walker is running it can replace TLB entries
         * at any time, leading to a race between it & the CPU.
         */
        if (cpu_has_htw)
                return true;

        /*
         * If the CPU shares FTLB RAM with its siblings then our entry may be
         * replaced at any time by a sibling performing a write to the FTLB.
         */
        if (cpu_has_shared_ftlb_ram)
                return true;

        /* In all other cases there ought to be no race condition to handle */
        return false;
}

/*
 * R4000 style TLB load/store/modify handlers.
 */
static struct work_registers
build_r4000_tlbchange_handler_head(u32 **p, struct uasm_label **l,
                                   struct uasm_reloc **r)
{
        struct work_registers wr = build_get_work_registers(p);

#ifdef CONFIG_64BIT
        build_get_pmde64(p, l, r, wr.r1, wr.r2); /* get pmd in ptr */
#else
        build_get_pgde32(p, wr.r1, wr.r2); /* get pgd in ptr */
#endif

#ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
        /*
         * For huge tlb entries, pmd doesn't contain an address but
         * instead contains the tlb pte. Check the PAGE_HUGE bit and
         * see if we need to jump to huge tlb processing.
         */
        build_is_huge_pte(p, r, wr.r1, wr.r2, label_tlb_huge_update);
#endif

        UASM_i_MFC0(p, wr.r1, C0_BADVADDR);
        UASM_i_LW(p, wr.r2, 0, wr.r2);
        UASM_i_SRL(p, wr.r1, wr.r1, PAGE_SHIFT + PTE_ORDER - PTE_T_LOG2);
        uasm_i_andi(p, wr.r1, wr.r1, (PTRS_PER_PTE - 1) << PTE_T_LOG2);
        UASM_i_ADDU(p, wr.r2, wr.r2, wr.r1);

#ifdef CONFIG_SMP
        uasm_l_smp_pgtable_change(l, *p);
#endif
        iPTE_LW(p, wr.r1, wr.r2); /* get even pte */
        if (!m4kc_tlbp_war()) {
                build_tlb_probe_entry(p);
                if (cpu_has_tlbex_tlbp_race()) {
                        /* race condition happens, leaving */
                        uasm_i_ehb(p);
                        uasm_i_mfc0(p, wr.r3, C0_INDEX);
                        uasm_il_bltz(p, r, wr.r3, label_leave);
                        uasm_i_nop(p);
                }
        }
        return wr;
}

static void
build_r4000_tlbchange_handler_tail(u32 **p, struct uasm_label **l,
                                   struct uasm_reloc **r, unsigned int tmp,
                                   unsigned int ptr)
{
        uasm_i_ori(p, ptr, ptr, sizeof(pte_t));
        uasm_i_xori(p, ptr, ptr, sizeof(pte_t));
        build_update_entries(p, tmp, ptr);
        build_tlb_write_entry(p, l, r, tlb_indexed);
        uasm_l_leave(l, *p);
        build_restore_work_registers(p);
        uasm_i_eret(p); /* return from trap */

#ifdef CONFIG_64BIT
        build_get_pgd_vmalloc64(p, l, r, tmp, ptr, not_refill);
#endif
}

static void build_r4000_tlb_load_handler(void)
{
        u32 *p = (u32 *)msk_isa16_mode((ulong)handle_tlbl);
        struct uasm_label *l = labels;
        struct uasm_reloc *r = relocs;
        struct work_registers wr;

        memset(p, 0, handle_tlbl_end - (char *)p);
        memset(labels, 0, sizeof(labels));
        memset(relocs, 0, sizeof(relocs));

        if (bcm1250_m3_war()) {
                unsigned int segbits = 44;

                uasm_i_dmfc0(&p, K0, C0_BADVADDR);
                uasm_i_dmfc0(&p, K1, C0_ENTRYHI);
                uasm_i_xor(&p, K0, K0, K1);
                uasm_i_dsrl_safe(&p, K1, K0, 62);
                uasm_i_dsrl_safe(&p, K0, K0, 12 + 1);
                uasm_i_dsll_safe(&p, K0, K0, 64 + 12 + 1 - segbits);
                uasm_i_or(&p, K0, K0, K1);
                uasm_il_bnez(&p, &r, K0, label_leave);
                /* No need for uasm_i_nop */
        }

        wr = build_r4000_tlbchange_handler_head(&p, &l, &r);
        build_pte_present(&p, &r, wr.r1, wr.r2, wr.r3, label_nopage_tlbl);
        if (m4kc_tlbp_war())
                build_tlb_probe_entry(&p);

        if (cpu_has_rixi && !cpu_has_rixiex) {
                /*
                 * If the page is not _PAGE_VALID, RI or XI could not
                 * have triggered it.  Skip the expensive test..
                 */
                if (use_bbit_insns()) {
                        uasm_il_bbit0(&p, &r, wr.r1, ilog2(_PAGE_VALID),
                                      label_tlbl_goaround1);
                } else {
                        uasm_i_andi(&p, wr.r3, wr.r1, _PAGE_VALID);
                        uasm_il_beqz(&p, &r, wr.r3, label_tlbl_goaround1);
                }
                uasm_i_nop(&p);

                /*
                 * Warn if something may race with us & replace the TLB entry
                 * before we read it here. Everything with such races should
                 * also have dedicated RiXi exception handlers, so this
                 * shouldn't be hit.
                 */
                WARN(cpu_has_tlbex_tlbp_race(), "Unhandled race in RiXi path");

                uasm_i_tlbr(&p);

                switch (current_cpu_type()) {
                default:
                        if (cpu_has_mips_r2_exec_hazard) {
                                uasm_i_ehb(&p);

                case CPU_CAVIUM_OCTEON:
                case CPU_CAVIUM_OCTEON_PLUS:
                case CPU_CAVIUM_OCTEON2:
                                break;
                        }
                }

                /* Examine  entrylo 0 or 1 based on ptr. */
                if (use_bbit_insns()) {
                        uasm_i_bbit0(&p, wr.r2, ilog2(sizeof(pte_t)), 8);
                } else {
                        uasm_i_andi(&p, wr.r3, wr.r2, sizeof(pte_t));
                        uasm_i_beqz(&p, wr.r3, 8);
                }
                /* load it in the delay slot*/
                UASM_i_MFC0(&p, wr.r3, C0_ENTRYLO0);
                /* load it if ptr is odd */
                UASM_i_MFC0(&p, wr.r3, C0_ENTRYLO1);
                /*
                 * If the entryLo (now in wr.r3) is valid (bit 1), RI or
                 * XI must have triggered it.
                 */
                if (use_bbit_insns()) {
                        uasm_il_bbit1(&p, &r, wr.r3, 1, label_nopage_tlbl);
                        uasm_i_nop(&p);
                        uasm_l_tlbl_goaround1(&l, p);
                } else {
                        uasm_i_andi(&p, wr.r3, wr.r3, 2);
                        uasm_il_bnez(&p, &r, wr.r3, label_nopage_tlbl);
                        uasm_i_nop(&p);
                }
                uasm_l_tlbl_goaround1(&l, p);
        }
        build_make_valid(&p, &r, wr.r1, wr.r2, wr.r3);
        build_r4000_tlbchange_handler_tail(&p, &l, &r, wr.r1, wr.r2);

#ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
        /*
         * This is the entry point when build_r4000_tlbchange_handler_head
         * spots a huge page.
         */
        uasm_l_tlb_huge_update(&l, p);
        iPTE_LW(&p, wr.r1, wr.r2);
        build_pte_present(&p, &r, wr.r1, wr.r2, wr.r3, label_nopage_tlbl);
        build_tlb_probe_entry(&p);

        if (cpu_has_rixi && !cpu_has_rixiex) {
                /*
                 * If the page is not _PAGE_VALID, RI or XI could not
                 * have triggered it.  Skip the expensive test..
                 */
                if (use_bbit_insns()) {
                        uasm_il_bbit0(&p, &r, wr.r1, ilog2(_PAGE_VALID),
                                      label_tlbl_goaround2);
                } else {
                        uasm_i_andi(&p, wr.r3, wr.r1, _PAGE_VALID);
                        uasm_il_beqz(&p, &r, wr.r3, label_tlbl_goaround2);
                }
                uasm_i_nop(&p);

                /*
                 * Warn if something may race with us & replace the TLB entry
                 * before we read it here. Everything with such races should
                 * also have dedicated RiXi exception handlers, so this
                 * shouldn't be hit.
                 */
                WARN(cpu_has_tlbex_tlbp_race(), "Unhandled race in RiXi path");

                uasm_i_tlbr(&p);

                switch (current_cpu_type()) {
                default:
                        if (cpu_has_mips_r2_exec_hazard) {
                                uasm_i_ehb(&p);

                case CPU_CAVIUM_OCTEON:
                case CPU_CAVIUM_OCTEON_PLUS:
                case CPU_CAVIUM_OCTEON2:
                                break;
                        }
                }

                /* Examine  entrylo 0 or 1 based on ptr. */
                if (use_bbit_insns()) {
                        uasm_i_bbit0(&p, wr.r2, ilog2(sizeof(pte_t)), 8);
                } else {
                        uasm_i_andi(&p, wr.r3, wr.r2, sizeof(pte_t));
                        uasm_i_beqz(&p, wr.r3, 8);
                }
                /* load it in the delay slot*/
                UASM_i_MFC0(&p, wr.r3, C0_ENTRYLO0);
                /* load it if ptr is odd */
                UASM_i_MFC0(&p, wr.r3, C0_ENTRYLO1);
                /*
                 * If the entryLo (now in wr.r3) is valid (bit 1), RI or
                 * XI must have triggered it.
                 */
                if (use_bbit_insns()) {
                        uasm_il_bbit0(&p, &r, wr.r3, 1, label_tlbl_goaround2);
                } else {
                        uasm_i_andi(&p, wr.r3, wr.r3, 2);
                        uasm_il_beqz(&p, &r, wr.r3, label_tlbl_goaround2);
                }
                if (PM_DEFAULT_MASK == 0)
                        uasm_i_nop(&p);
                /*
                 * We clobbered C0_PAGEMASK, restore it.  On the other branch
                 * it is restored in build_huge_tlb_write_entry.
                 */
                build_restore_pagemask(&p, &r, wr.r3, label_nopage_tlbl, 0);

                uasm_l_tlbl_goaround2(&l, p);
        }
        uasm_i_ori(&p, wr.r1, wr.r1, (_PAGE_ACCESSED | _PAGE_VALID));
        build_huge_handler_tail(&p, &r, &l, wr.r1, wr.r2, 1);
#endif

        uasm_l_nopage_tlbl(&l, p);
        if (IS_ENABLED(CONFIG_CPU_LOONGSON3_WORKAROUNDS))
                uasm_i_sync(&p, 0);
        build_restore_work_registers(&p);
#ifdef CONFIG_CPU_MICROMIPS
        if ((unsigned long)tlb_do_page_fault_0 & 1) {
                uasm_i_lui(&p, K0, uasm_rel_hi((long)tlb_do_page_fault_0));
                uasm_i_addiu(&p, K0, K0, uasm_rel_lo((long)tlb_do_page_fault_0));
                uasm_i_jr(&p, K0);
        } else
#endif
        uasm_i_j(&p, (unsigned long)tlb_do_page_fault_0 & 0x0fffffff);
        uasm_i_nop(&p);

        if (p >= (u32 *)handle_tlbl_end)
                panic("TLB load handler fastpath space exceeded");

        uasm_resolve_relocs(relocs, labels);
        pr_debug("Wrote TLB load handler fastpath (%u instructions).\n",
                 (unsigned int)(p - (u32 *)handle_tlbl));

        dump_handler("r4000_tlb_load", handle_tlbl, handle_tlbl_end);
}

static void build_r4000_tlb_store_handler(void)
{
        u32 *p = (u32 *)msk_isa16_mode((ulong)handle_tlbs);
        struct uasm_label *l = labels;
        struct uasm_reloc *r = relocs;
        struct work_registers wr;

        memset(p, 0, handle_tlbs_end - (char *)p);
        memset(labels, 0, sizeof(labels));
        memset(relocs, 0, sizeof(relocs));

        wr = build_r4000_tlbchange_handler_head(&p, &l, &r);
        build_pte_writable(&p, &r, wr.r1, wr.r2, wr.r3, label_nopage_tlbs);
        if (m4kc_tlbp_war())
                build_tlb_probe_entry(&p);
        build_make_write(&p, &r, wr.r1, wr.r2, wr.r3);
        build_r4000_tlbchange_handler_tail(&p, &l, &r, wr.r1, wr.r2);

#ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
        /*
         * This is the entry point when
         * build_r4000_tlbchange_handler_head spots a huge page.
         */
        uasm_l_tlb_huge_update(&l, p);
        iPTE_LW(&p, wr.r1, wr.r2);
        build_pte_writable(&p, &r, wr.r1, wr.r2, wr.r3, label_nopage_tlbs);
        build_tlb_probe_entry(&p);
        uasm_i_ori(&p, wr.r1, wr.r1,
                   _PAGE_ACCESSED | _PAGE_MODIFIED | _PAGE_VALID | _PAGE_DIRTY);
        build_huge_handler_tail(&p, &r, &l, wr.r1, wr.r2, 1);
#endif

        uasm_l_nopage_tlbs(&l, p);
        if (IS_ENABLED(CONFIG_CPU_LOONGSON3_WORKAROUNDS))
                uasm_i_sync(&p, 0);
        build_restore_work_registers(&p);
#ifdef CONFIG_CPU_MICROMIPS
        if ((unsigned long)tlb_do_page_fault_1 & 1) {
                uasm_i_lui(&p, K0, uasm_rel_hi((long)tlb_do_page_fault_1));
                uasm_i_addiu(&p, K0, K0, uasm_rel_lo((long)tlb_do_page_fault_1));
                uasm_i_jr(&p, K0);
        } else
#endif
        uasm_i_j(&p, (unsigned long)tlb_do_page_fault_1 & 0x0fffffff);
        uasm_i_nop(&p);

        if (p >= (u32 *)handle_tlbs_end)
                panic("TLB store handler fastpath space exceeded");

        uasm_resolve_relocs(relocs, labels);
        pr_debug("Wrote TLB store handler fastpath (%u instructions).\n",
                 (unsigned int)(p - (u32 *)handle_tlbs));

        dump_handler("r4000_tlb_store", handle_tlbs, handle_tlbs_end);
}

static void build_r4000_tlb_modify_handler(void)
{
        u32 *p = (u32 *)msk_isa16_mode((ulong)handle_tlbm);
        struct uasm_label *l = labels;
        struct uasm_reloc *r = relocs;
        struct work_registers wr;

        memset(p, 0, handle_tlbm_end - (char *)p);
        memset(labels, 0, sizeof(labels));
        memset(relocs, 0, sizeof(relocs));

        wr = build_r4000_tlbchange_handler_head(&p, &l, &r);
        build_pte_modifiable(&p, &r, wr.r1, wr.r2, wr.r3, label_nopage_tlbm);
        if (m4kc_tlbp_war())
                build_tlb_probe_entry(&p);
        /* Present and writable bits set, set accessed and dirty bits. */
        build_make_write(&p, &r, wr.r1, wr.r2, wr.r3);
        build_r4000_tlbchange_handler_tail(&p, &l, &r, wr.r1, wr.r2);

#ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
        /*
         * This is the entry point when
         * build_r4000_tlbchange_handler_head spots a huge page.
         */
        uasm_l_tlb_huge_update(&l, p);
        iPTE_LW(&p, wr.r1, wr.r2);
        build_pte_modifiable(&p, &r, wr.r1, wr.r2,  wr.r3, label_nopage_tlbm);
        build_tlb_probe_entry(&p);
        uasm_i_ori(&p, wr.r1, wr.r1,
                   _PAGE_ACCESSED | _PAGE_MODIFIED | _PAGE_VALID | _PAGE_DIRTY);
        build_huge_handler_tail(&p, &r, &l, wr.r1, wr.r2, 0);
#endif

        uasm_l_nopage_tlbm(&l, p);
        if (IS_ENABLED(CONFIG_CPU_LOONGSON3_WORKAROUNDS))
                uasm_i_sync(&p, 0);
        build_restore_work_registers(&p);
#ifdef CONFIG_CPU_MICROMIPS
        if ((unsigned long)tlb_do_page_fault_1 & 1) {
                uasm_i_lui(&p, K0, uasm_rel_hi((long)tlb_do_page_fault_1));
                uasm_i_addiu(&p, K0, K0, uasm_rel_lo((long)tlb_do_page_fault_1));
                uasm_i_jr(&p, K0);
        } else
#endif
        uasm_i_j(&p, (unsigned long)tlb_do_page_fault_1 & 0x0fffffff);
        uasm_i_nop(&p);

        if (p >= (u32 *)handle_tlbm_end)
                panic("TLB modify handler fastpath space exceeded");

        uasm_resolve_relocs(relocs, labels);
        pr_debug("Wrote TLB modify handler fastpath (%u instructions).\n",
                 (unsigned int)(p - (u32 *)handle_tlbm));

        dump_handler("r4000_tlb_modify", handle_tlbm, handle_tlbm_end);
}

static void flush_tlb_handlers(void)
{
        local_flush_icache_range((unsigned long)handle_tlbl,
                           (unsigned long)handle_tlbl_end);
        local_flush_icache_range((unsigned long)handle_tlbs,
                           (unsigned long)handle_tlbs_end);
        local_flush_icache_range((unsigned long)handle_tlbm,
                           (unsigned long)handle_tlbm_end);
        local_flush_icache_range((unsigned long)tlbmiss_handler_setup_pgd,
                           (unsigned long)tlbmiss_handler_setup_pgd_end);
}

static void print_htw_config(void)
{
        unsigned long config;
        unsigned int pwctl;
        const int field = 2 * sizeof(unsigned long);

        config = read_c0_pwfield();
        pr_debug("PWField (0x%0*lx): GDI: 0x%02lx  UDI: 0x%02lx  MDI: 0x%02lx  PTI: 0x%02lx  PTEI: 0x%02lx\n",
                field, config,
                (config & MIPS_PWFIELD_GDI_MASK) >> MIPS_PWFIELD_GDI_SHIFT,
                (config & MIPS_PWFIELD_UDI_MASK) >> MIPS_PWFIELD_UDI_SHIFT,
                (config & MIPS_PWFIELD_MDI_MASK) >> MIPS_PWFIELD_MDI_SHIFT,
                (config & MIPS_PWFIELD_PTI_MASK) >> MIPS_PWFIELD_PTI_SHIFT,
                (config & MIPS_PWFIELD_PTEI_MASK) >> MIPS_PWFIELD_PTEI_SHIFT);

        config = read_c0_pwsize();
        pr_debug("PWSize  (0x%0*lx): PS: 0x%lx  GDW: 0x%02lx  UDW: 0x%02lx  MDW: 0x%02lx  PTW: 0x%02lx  PTEW: 0x%02lx\n",
                field, config,
                (config & MIPS_PWSIZE_PS_MASK) >> MIPS_PWSIZE_PS_SHIFT,
                (config & MIPS_PWSIZE_GDW_MASK) >> MIPS_PWSIZE_GDW_SHIFT,
                (config & MIPS_PWSIZE_UDW_MASK) >> MIPS_PWSIZE_UDW_SHIFT,
                (config & MIPS_PWSIZE_MDW_MASK) >> MIPS_PWSIZE_MDW_SHIFT,
                (config & MIPS_PWSIZE_PTW_MASK) >> MIPS_PWSIZE_PTW_SHIFT,
                (config & MIPS_PWSIZE_PTEW_MASK) >> MIPS_PWSIZE_PTEW_SHIFT);

        pwctl = read_c0_pwctl();
        pr_debug("PWCtl   (0x%x): PWEn: 0x%x  XK: 0x%x  XS: 0x%x  XU: 0x%x  DPH: 0x%x  HugePg: 0x%x  Psn: 0x%x\n",
                pwctl,
                (pwctl & MIPS_PWCTL_PWEN_MASK) >> MIPS_PWCTL_PWEN_SHIFT,
                (pwctl & MIPS_PWCTL_XK_MASK) >> MIPS_PWCTL_XK_SHIFT,
                (pwctl & MIPS_PWCTL_XS_MASK) >> MIPS_PWCTL_XS_SHIFT,
                (pwctl & MIPS_PWCTL_XU_MASK) >> MIPS_PWCTL_XU_SHIFT,
                (pwctl & MIPS_PWCTL_DPH_MASK) >> MIPS_PWCTL_DPH_SHIFT,
                (pwctl & MIPS_PWCTL_HUGEPG_MASK) >> MIPS_PWCTL_HUGEPG_SHIFT,
                (pwctl & MIPS_PWCTL_PSN_MASK) >> MIPS_PWCTL_PSN_SHIFT);
}

static void config_htw_params(void)
{
        unsigned long pwfield, pwsize, ptei;
        unsigned int config;

        /*
         * We are using 2-level page tables, so we only need to
         * setup GDW and PTW appropriately. UDW and MDW will remain 0.
         * The default value of GDI/UDI/MDI/PTI is 0xc. It is illegal to
         * write values less than 0xc in these fields because the entire
         * write will be dropped. As a result of which, we must preserve
         * the original reset values and overwrite only what we really want.
         */

        pwfield = read_c0_pwfield();
        /* re-initialize the GDI field */
        pwfield &= ~MIPS_PWFIELD_GDI_MASK;
        pwfield |= PGDIR_SHIFT << MIPS_PWFIELD_GDI_SHIFT;
        /* re-initialize the PTI field including the even/odd bit */
        pwfield &= ~MIPS_PWFIELD_PTI_MASK;
        pwfield |= PAGE_SHIFT << MIPS_PWFIELD_PTI_SHIFT;
        if (CONFIG_PGTABLE_LEVELS >= 3) {
                pwfield &= ~MIPS_PWFIELD_MDI_MASK;
                pwfield |= PMD_SHIFT << MIPS_PWFIELD_MDI_SHIFT;
        }
        /* Set the PTEI right shift */
        ptei = _PAGE_GLOBAL_SHIFT << MIPS_PWFIELD_PTEI_SHIFT;
        pwfield |= ptei;
        write_c0_pwfield(pwfield);
        /* Check whether the PTEI value is supported */
        back_to_back_c0_hazard();
        pwfield = read_c0_pwfield();
        if (((pwfield & MIPS_PWFIELD_PTEI_MASK) << MIPS_PWFIELD_PTEI_SHIFT)
                != ptei) {
                pr_warn("Unsupported PTEI field value: 0x%lx. HTW will not be enabled",
                        ptei);
                /*
                 * Drop option to avoid HTW being enabled via another path
                 * (eg htw_reset())
                 */
                current_cpu_data.options &= ~MIPS_CPU_HTW;
                return;
        }

        pwsize = ilog2(PTRS_PER_PGD) << MIPS_PWSIZE_GDW_SHIFT;
        pwsize |= ilog2(PTRS_PER_PTE) << MIPS_PWSIZE_PTW_SHIFT;
        if (CONFIG_PGTABLE_LEVELS >= 3)
                pwsize |= ilog2(PTRS_PER_PMD) << MIPS_PWSIZE_MDW_SHIFT;

        /* Set pointer size to size of directory pointers */
        if (IS_ENABLED(CONFIG_64BIT))
                pwsize |= MIPS_PWSIZE_PS_MASK;
        /* PTEs may be multiple pointers long (e.g. with XPA) */
        pwsize |= ((PTE_T_LOG2 - PGD_T_LOG2) << MIPS_PWSIZE_PTEW_SHIFT)
                        & MIPS_PWSIZE_PTEW_MASK;

        write_c0_pwsize(pwsize);

        /* Make sure everything is set before we enable the HTW */
        back_to_back_c0_hazard();

        /*
         * Enable HTW (and only for XUSeg on 64-bit), and disable the rest of
         * the pwctl fields.
         */
        config = 1 << MIPS_PWCTL_PWEN_SHIFT;
        if (IS_ENABLED(CONFIG_64BIT))
                config |= MIPS_PWCTL_XU_MASK;
        write_c0_pwctl(config);
        pr_info("Hardware Page Table Walker enabled\n");

        print_htw_config();
}

static void config_xpa_params(void)
{
#ifdef CONFIG_XPA
        unsigned int pagegrain;

        if (mips_xpa_disabled) {
                pr_info("Extended Physical Addressing (XPA) disabled\n");
                return;
        }

        pagegrain = read_c0_pagegrain();
        write_c0_pagegrain(pagegrain | PG_ELPA);
        back_to_back_c0_hazard();
        pagegrain = read_c0_pagegrain();

        if (pagegrain & PG_ELPA)
                pr_info("Extended Physical Addressing (XPA) enabled\n");
        else
                panic("Extended Physical Addressing (XPA) disabled");
#endif
}

static void check_pabits(void)
{
        unsigned long entry;
        unsigned pabits, fillbits;

        if (!cpu_has_rixi || !_PAGE_NO_EXEC) {
                /*
                 * We'll only be making use of the fact that we can rotate bits
                 * into the fill if the CPU supports RIXI, so don't bother
                 * probing this for CPUs which don't.
                 */
                return;
        }

        write_c0_entrylo0(~0ul);
        back_to_back_c0_hazard();
        entry = read_c0_entrylo0();

        /* clear all non-PFN bits */
        entry &= ~((1 << MIPS_ENTRYLO_PFN_SHIFT) - 1);
        entry &= ~(MIPS_ENTRYLO_RI | MIPS_ENTRYLO_XI);

        /* find a lower bound on PABITS, and upper bound on fill bits */
        pabits = fls_long(entry) + 6;
        fillbits = max_t(int, (int)BITS_PER_LONG - pabits, 0);

        /* minus the RI & XI bits */
        fillbits -= min_t(unsigned, fillbits, 2);

        if (fillbits >= ilog2(_PAGE_NO_EXEC))
                fill_includes_sw_bits = true;

        pr_debug("Entry* registers contain %u fill bits\n", fillbits);
}

void build_tlb_refill_handler(void)
{
        /*
         * The refill handler is generated per-CPU, multi-node systems
         * may have local storage for it. The other handlers are only
         * needed once.
         */
        static int run_once = 0;

        if (IS_ENABLED(CONFIG_XPA) && !cpu_has_rixi)
                panic("Kernels supporting XPA currently require CPUs with RIXI");

        output_pgtable_bits_defines();
        check_pabits();

#ifdef CONFIG_64BIT
        check_for_high_segbits = current_cpu_data.vmbits > (PGDIR_SHIFT + PGD_ORDER + PAGE_SHIFT - 3);
#endif

        if (cpu_has_3kex) {
#ifndef CONFIG_MIPS_PGD_C0_CONTEXT
                if (!run_once) {
                        build_setup_pgd();
                        build_r3000_tlb_refill_handler();
                        build_r3000_tlb_load_handler();
                        build_r3000_tlb_store_handler();
                        build_r3000_tlb_modify_handler();
                        flush_tlb_handlers();
                        run_once++;
                }
#else
                panic("No R3000 TLB refill handler");
#endif
                return;
        }

        if (cpu_has_ldpte)
                setup_pw();

        if (!run_once) {
                scratch_reg = allocate_kscratch();
                build_setup_pgd();
                build_r4000_tlb_load_handler();
                build_r4000_tlb_store_handler();
                build_r4000_tlb_modify_handler();
                if (cpu_has_ldpte)
                        build_loongson3_tlb_refill_handler();
                else
                        build_r4000_tlb_refill_handler();
                flush_tlb_handlers();
                run_once++;
        }
        if (cpu_has_xpa)
                config_xpa_params();
        if (cpu_has_htw)
                config_htw_params();
}