[mirror_ubuntu-jammy-kernel.git] / arch / powerpc / mm / tlb_nohash.c

/*
 * This file contains the routines for TLB flushing.
 * On machines where the MMU does not use a hash table to store virtual to
 * physical translations (ie, SW loaded TLBs or Book3E compilant processors,
 * this does -not- include 603 however which shares the implementation with
 * hash based processors)
 *
 *  -- BenH
 *
 * Copyright 2008,2009 Ben Herrenschmidt <benh@kernel.crashing.org>
 *                     IBM Corp.
 *
 *  Derived from arch/ppc/mm/init.c:
 *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
 *
 *  Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
 *  and Cort Dougan (PReP) (cort@cs.nmt.edu)
 *    Copyright (C) 1996 Paul Mackerras
 *
 *  Derived from "arch/i386/mm/init.c"
 *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 *
 */

#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/mm.h>
#include <linux/init.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/preempt.h>
#include <linux/spinlock.h>
#include <linux/memblock.h>
#include <linux/of_fdt.h>
#include <linux/hugetlb.h>

#include <asm/tlbflush.h>
#include <asm/tlb.h>
#include <asm/code-patching.h>
#include <asm/cputhreads.h>
#include <asm/hugetlb.h>
#include <asm/paca.h>

#include "mmu_decl.h"

/*
 * This struct lists the sw-supported page sizes.  The hardawre MMU may support
 * other sizes not listed here.   The .ind field is only used on MMUs that have
 * indirect page table entries.
 */
#if defined(CONFIG_PPC_BOOK3E_MMU) || defined(CONFIG_PPC_8xx)
#ifdef CONFIG_PPC_FSL_BOOK3E
struct mmu_psize_def mmu_psize_defs[MMU_PAGE_COUNT] = {
        [MMU_PAGE_4K] = {
                .shift  = 12,
                .enc    = BOOK3E_PAGESZ_4K,
        },
        [MMU_PAGE_2M] = {
                .shift  = 21,
                .enc    = BOOK3E_PAGESZ_2M,
        },
        [MMU_PAGE_4M] = {
                .shift  = 22,
                .enc    = BOOK3E_PAGESZ_4M,
        },
        [MMU_PAGE_16M] = {
                .shift  = 24,
                .enc    = BOOK3E_PAGESZ_16M,
        },
        [MMU_PAGE_64M] = {
                .shift  = 26,
                .enc    = BOOK3E_PAGESZ_64M,
        },
        [MMU_PAGE_256M] = {
                .shift  = 28,
                .enc    = BOOK3E_PAGESZ_256M,
        },
        [MMU_PAGE_1G] = {
                .shift  = 30,
                .enc    = BOOK3E_PAGESZ_1GB,
        },
};
#elif defined(CONFIG_PPC_8xx)
struct mmu_psize_def mmu_psize_defs[MMU_PAGE_COUNT] = {
        /* we only manage 4k and 16k pages as normal pages */
#ifdef CONFIG_PPC_4K_PAGES
        [MMU_PAGE_4K] = {
                .shift  = 12,
        },
#else
        [MMU_PAGE_16K] = {
                .shift  = 14,
        },
#endif
};
#else
struct mmu_psize_def mmu_psize_defs[MMU_PAGE_COUNT] = {
        [MMU_PAGE_4K] = {
                .shift  = 12,
                .ind    = 20,
                .enc    = BOOK3E_PAGESZ_4K,
        },
        [MMU_PAGE_16K] = {
                .shift  = 14,
                .enc    = BOOK3E_PAGESZ_16K,
        },
        [MMU_PAGE_64K] = {
                .shift  = 16,
                .ind    = 28,
                .enc    = BOOK3E_PAGESZ_64K,
        },
        [MMU_PAGE_1M] = {
                .shift  = 20,
                .enc    = BOOK3E_PAGESZ_1M,
        },
        [MMU_PAGE_16M] = {
                .shift  = 24,
                .ind    = 36,
                .enc    = BOOK3E_PAGESZ_16M,
        },
        [MMU_PAGE_256M] = {
                .shift  = 28,
                .enc    = BOOK3E_PAGESZ_256M,
        },
        [MMU_PAGE_1G] = {
                .shift  = 30,
                .enc    = BOOK3E_PAGESZ_1GB,
        },
};
#endif /* CONFIG_FSL_BOOKE */

static inline int mmu_get_tsize(int psize)
{
        return mmu_psize_defs[psize].enc;
}
#else
static inline int mmu_get_tsize(int psize)
{
        /* This isn't used on !Book3E for now */
        return 0;
}
#endif /* CONFIG_PPC_BOOK3E_MMU */

/* The variables below are currently only used on 64-bit Book3E
 * though this will probably be made common with other nohash
 * implementations at some point
 */
#ifdef CONFIG_PPC64

int mmu_linear_psize;           /* Page size used for the linear mapping */
int mmu_pte_psize;              /* Page size used for PTE pages */
int mmu_vmemmap_psize;          /* Page size used for the virtual mem map */
int book3e_htw_mode;            /* HW tablewalk?  Value is PPC_HTW_* */
unsigned long linear_map_top;   /* Top of linear mapping */


/*
 * Number of bytes to add to SPRN_SPRG_TLB_EXFRAME on crit/mcheck/debug
 * exceptions.  This is used for bolted and e6500 TLB miss handlers which
 * do not modify this SPRG in the TLB miss code; for other TLB miss handlers,
 * this is set to zero.
 */
int extlb_level_exc;

#endif /* CONFIG_PPC64 */

#ifdef CONFIG_PPC_FSL_BOOK3E
/* next_tlbcam_idx is used to round-robin tlbcam entry assignment */
DEFINE_PER_CPU(int, next_tlbcam_idx);
EXPORT_PER_CPU_SYMBOL(next_tlbcam_idx);
#endif

/*
 * Base TLB flushing operations:
 *
 *  - flush_tlb_mm(mm) flushes the specified mm context TLB's
 *  - flush_tlb_page(vma, vmaddr) flushes one page
 *  - flush_tlb_range(vma, start, end) flushes a range of pages
 *  - flush_tlb_kernel_range(start, end) flushes kernel pages
 *
 *  - local_* variants of page and mm only apply to the current
 *    processor
 */

/*
 * These are the base non-SMP variants of page and mm flushing
 */
void local_flush_tlb_mm(struct mm_struct *mm)
{
        unsigned int pid;

        preempt_disable();
        pid = mm->context.id;
        if (pid != MMU_NO_CONTEXT)
                _tlbil_pid(pid);
        preempt_enable();
}
EXPORT_SYMBOL(local_flush_tlb_mm);

void __local_flush_tlb_page(struct mm_struct *mm, unsigned long vmaddr,
                            int tsize, int ind)
{
        unsigned int pid;

        preempt_disable();
        pid = mm ? mm->context.id : 0;
        if (pid != MMU_NO_CONTEXT)
                _tlbil_va(vmaddr, pid, tsize, ind);
        preempt_enable();
}

void local_flush_tlb_page(struct vm_area_struct *vma, unsigned long vmaddr)
{
        __local_flush_tlb_page(vma ? vma->vm_mm : NULL, vmaddr,
                               mmu_get_tsize(mmu_virtual_psize), 0);
}
EXPORT_SYMBOL(local_flush_tlb_page);

/*
 * And here are the SMP non-local implementations
 */
#ifdef CONFIG_SMP

static DEFINE_RAW_SPINLOCK(tlbivax_lock);

struct tlb_flush_param {
        unsigned long addr;
        unsigned int pid;
        unsigned int tsize;
        unsigned int ind;
};

static void do_flush_tlb_mm_ipi(void *param)
{
        struct tlb_flush_param *p = param;

        _tlbil_pid(p ? p->pid : 0);
}

static void do_flush_tlb_page_ipi(void *param)
{
        struct tlb_flush_param *p = param;

        _tlbil_va(p->addr, p->pid, p->tsize, p->ind);
}


/* Note on invalidations and PID:
 *
 * We snapshot the PID with preempt disabled. At this point, it can still
 * change either because:
 * - our context is being stolen (PID -> NO_CONTEXT) on another CPU
 * - we are invaliating some target that isn't currently running here
 *   and is concurrently acquiring a new PID on another CPU
 * - some other CPU is re-acquiring a lost PID for this mm
 * etc...
 *
 * However, this shouldn't be a problem as we only guarantee
 * invalidation of TLB entries present prior to this call, so we
 * don't care about the PID changing, and invalidating a stale PID
 * is generally harmless.
 */

void flush_tlb_mm(struct mm_struct *mm)
{
        unsigned int pid;

        preempt_disable();
        pid = mm->context.id;
        if (unlikely(pid == MMU_NO_CONTEXT))
                goto no_context;
        if (!mm_is_core_local(mm)) {
                struct tlb_flush_param p = { .pid = pid };
                /* Ignores smp_processor_id() even if set. */
                smp_call_function_many(mm_cpumask(mm),
                                       do_flush_tlb_mm_ipi, &p, 1);
        }
        _tlbil_pid(pid);
 no_context:
        preempt_enable();
}
EXPORT_SYMBOL(flush_tlb_mm);

void __flush_tlb_page(struct mm_struct *mm, unsigned long vmaddr,
                      int tsize, int ind)
{
        struct cpumask *cpu_mask;
        unsigned int pid;

        /*
         * This function as well as __local_flush_tlb_page() must only be called
         * for user contexts.
         */
        if (unlikely(WARN_ON(!mm)))
                return;

        preempt_disable();
        pid = mm->context.id;
        if (unlikely(pid == MMU_NO_CONTEXT))
                goto bail;
        cpu_mask = mm_cpumask(mm);
        if (!mm_is_core_local(mm)) {
                /* If broadcast tlbivax is supported, use it */
                if (mmu_has_feature(MMU_FTR_USE_TLBIVAX_BCAST)) {
                        int lock = mmu_has_feature(MMU_FTR_LOCK_BCAST_INVAL);
                        if (lock)
                                raw_spin_lock(&tlbivax_lock);
                        _tlbivax_bcast(vmaddr, pid, tsize, ind);
                        if (lock)
                                raw_spin_unlock(&tlbivax_lock);
                        goto bail;
                } else {
                        struct tlb_flush_param p = {
                                .pid = pid,
                                .addr = vmaddr,
                                .tsize = tsize,
                                .ind = ind,
                        };
                        /* Ignores smp_processor_id() even if set in cpu_mask */
                        smp_call_function_many(cpu_mask,
                                               do_flush_tlb_page_ipi, &p, 1);
                }
        }
        _tlbil_va(vmaddr, pid, tsize, ind);
 bail:
        preempt_enable();
}

void flush_tlb_page(struct vm_area_struct *vma, unsigned long vmaddr)
{
#ifdef CONFIG_HUGETLB_PAGE
        if (vma && is_vm_hugetlb_page(vma))
                flush_hugetlb_page(vma, vmaddr);
#endif

        __flush_tlb_page(vma ? vma->vm_mm : NULL, vmaddr,
                         mmu_get_tsize(mmu_virtual_psize), 0);
}
EXPORT_SYMBOL(flush_tlb_page);

#endif /* CONFIG_SMP */

#ifdef CONFIG_PPC_47x
void __init early_init_mmu_47x(void)
{
#ifdef CONFIG_SMP
        unsigned long root = of_get_flat_dt_root();
        if (of_get_flat_dt_prop(root, "cooperative-partition", NULL))
                mmu_clear_feature(MMU_FTR_USE_TLBIVAX_BCAST);
#endif /* CONFIG_SMP */
}
#endif /* CONFIG_PPC_47x */

/*
 * Flush kernel TLB entries in the given range
 */
void flush_tlb_kernel_range(unsigned long start, unsigned long end)
{
#ifdef CONFIG_SMP
        preempt_disable();
        smp_call_function(do_flush_tlb_mm_ipi, NULL, 1);
        _tlbil_pid(0);
        preempt_enable();
#else
        _tlbil_pid(0);
#endif
}
EXPORT_SYMBOL(flush_tlb_kernel_range);

/*
 * Currently, for range flushing, we just do a full mm flush. This should
 * be optimized based on a threshold on the size of the range, since
 * some implementation can stack multiple tlbivax before a tlbsync but
 * for now, we keep it that way
 */
void flush_tlb_range(struct vm_area_struct *vma, unsigned long start,
                     unsigned long end)

{
        if (end - start == PAGE_SIZE && !(start & ~PAGE_MASK))
                flush_tlb_page(vma, start);
        else
                flush_tlb_mm(vma->vm_mm);
}
EXPORT_SYMBOL(flush_tlb_range);

void tlb_flush(struct mmu_gather *tlb)
{
        flush_tlb_mm(tlb->mm);
}

/*
 * Below are functions specific to the 64-bit variant of Book3E though that
 * may change in the future
 */

#ifdef CONFIG_PPC64

/*
 * Handling of virtual linear page tables or indirect TLB entries
 * flushing when PTE pages are freed
 */
void tlb_flush_pgtable(struct mmu_gather *tlb, unsigned long address)
{
        int tsize = mmu_psize_defs[mmu_pte_psize].enc;

        if (book3e_htw_mode != PPC_HTW_NONE) {
                unsigned long start = address & PMD_MASK;
                unsigned long end = address + PMD_SIZE;
                unsigned long size = 1UL << mmu_psize_defs[mmu_pte_psize].shift;

                /* This isn't the most optimal, ideally we would factor out the
                 * while preempt & CPU mask mucking around, or even the IPI but
                 * it will do for now
                 */
                while (start < end) {
                        __flush_tlb_page(tlb->mm, start, tsize, 1);
                        start += size;
                }
        } else {
                unsigned long rmask = 0xf000000000000000ul;
                unsigned long rid = (address & rmask) | 0x1000000000000000ul;
                unsigned long vpte = address & ~rmask;

#ifdef CONFIG_PPC_64K_PAGES
                vpte = (vpte >> (PAGE_SHIFT - 4)) & ~0xfffful;
#else
                vpte = (vpte >> (PAGE_SHIFT - 3)) & ~0xffful;
#endif
                vpte |= rid;
                __flush_tlb_page(tlb->mm, vpte, tsize, 0);
        }
}

static void setup_page_sizes(void)
{
        unsigned int tlb0cfg;
        unsigned int tlb0ps;
        unsigned int eptcfg;
        int i, psize;

#ifdef CONFIG_PPC_FSL_BOOK3E
        unsigned int mmucfg = mfspr(SPRN_MMUCFG);
        int fsl_mmu = mmu_has_feature(MMU_FTR_TYPE_FSL_E);

        if (fsl_mmu && (mmucfg & MMUCFG_MAVN) == MMUCFG_MAVN_V1) {
                unsigned int tlb1cfg = mfspr(SPRN_TLB1CFG);
                unsigned int min_pg, max_pg;

                min_pg = (tlb1cfg & TLBnCFG_MINSIZE) >> TLBnCFG_MINSIZE_SHIFT;
                max_pg = (tlb1cfg & TLBnCFG_MAXSIZE) >> TLBnCFG_MAXSIZE_SHIFT;

                for (psize = 0; psize < MMU_PAGE_COUNT; ++psize) {
                        struct mmu_psize_def *def;
                        unsigned int shift;

                        def = &mmu_psize_defs[psize];
                        shift = def->shift;

                        if (shift == 0 || shift & 1)
                                continue;

                        /* adjust to be in terms of 4^shift Kb */
                        shift = (shift - 10) >> 1;

                        if ((shift >= min_pg) && (shift <= max_pg))
                                def->flags |= MMU_PAGE_SIZE_DIRECT;
                }

                goto out;
        }

        if (fsl_mmu && (mmucfg & MMUCFG_MAVN) == MMUCFG_MAVN_V2) {
                u32 tlb1cfg, tlb1ps;

                tlb0cfg = mfspr(SPRN_TLB0CFG);
                tlb1cfg = mfspr(SPRN_TLB1CFG);
                tlb1ps = mfspr(SPRN_TLB1PS);
                eptcfg = mfspr(SPRN_EPTCFG);

                if ((tlb1cfg & TLBnCFG_IND) && (tlb0cfg & TLBnCFG_PT))
                        book3e_htw_mode = PPC_HTW_E6500;

                /*
                 * We expect 4K subpage size and unrestricted indirect size.
                 * The lack of a restriction on indirect size is a Freescale
                 * extension, indicated by PSn = 0 but SPSn != 0.
                 */
                if (eptcfg != 2)
                        book3e_htw_mode = PPC_HTW_NONE;

                for (psize = 0; psize < MMU_PAGE_COUNT; ++psize) {
                        struct mmu_psize_def *def = &mmu_psize_defs[psize];

                        if (!def->shift)
                                continue;

                        if (tlb1ps & (1U << (def->shift - 10))) {
                                def->flags |= MMU_PAGE_SIZE_DIRECT;

                                if (book3e_htw_mode && psize == MMU_PAGE_2M)
                                        def->flags |= MMU_PAGE_SIZE_INDIRECT;
                        }
                }

                goto out;
        }
#endif

        tlb0cfg = mfspr(SPRN_TLB0CFG);
        tlb0ps = mfspr(SPRN_TLB0PS);
        eptcfg = mfspr(SPRN_EPTCFG);

        /* Look for supported direct sizes */
        for (psize = 0; psize < MMU_PAGE_COUNT; ++psize) {
                struct mmu_psize_def *def = &mmu_psize_defs[psize];

                if (tlb0ps & (1U << (def->shift - 10)))
                        def->flags |= MMU_PAGE_SIZE_DIRECT;
        }

        /* Indirect page sizes supported ? */
        if ((tlb0cfg & TLBnCFG_IND) == 0 ||
            (tlb0cfg & TLBnCFG_PT) == 0)
                goto out;

        book3e_htw_mode = PPC_HTW_IBM;

        /* Now, we only deal with one IND page size for each
         * direct size. Hopefully all implementations today are
         * unambiguous, but we might want to be careful in the
         * future.
         */
        for (i = 0; i < 3; i++) {
                unsigned int ps, sps;

                sps = eptcfg & 0x1f;
                eptcfg >>= 5;
                ps = eptcfg & 0x1f;
                eptcfg >>= 5;
                if (!ps || !sps)
                        continue;
                for (psize = 0; psize < MMU_PAGE_COUNT; psize++) {
                        struct mmu_psize_def *def = &mmu_psize_defs[psize];

                        if (ps == (def->shift - 10))
                                def->flags |= MMU_PAGE_SIZE_INDIRECT;
                        if (sps == (def->shift - 10))
                                def->ind = ps + 10;
                }
        }

out:
        /* Cleanup array and print summary */
        pr_info("MMU: Supported page sizes\n");
        for (psize = 0; psize < MMU_PAGE_COUNT; ++psize) {
                struct mmu_psize_def *def = &mmu_psize_defs[psize];
                const char *__page_type_names[] = {
                        "unsupported",
                        "direct",
                        "indirect",
                        "direct & indirect"
                };
                if (def->flags == 0) {
                        def->shift = 0; 
                        continue;
                }
                pr_info("  %8ld KB as %s\n", 1ul << (def->shift - 10),
                        __page_type_names[def->flags & 0x3]);
        }
}

static void setup_mmu_htw(void)
{
        /*
         * If we want to use HW tablewalk, enable it by patching the TLB miss
         * handlers to branch to the one dedicated to it.
         */

        switch (book3e_htw_mode) {
        case PPC_HTW_IBM:
                patch_exception(0x1c0, exc_data_tlb_miss_htw_book3e);
                patch_exception(0x1e0, exc_instruction_tlb_miss_htw_book3e);
                break;
#ifdef CONFIG_PPC_FSL_BOOK3E
        case PPC_HTW_E6500:
                extlb_level_exc = EX_TLB_SIZE;
                patch_exception(0x1c0, exc_data_tlb_miss_e6500_book3e);
                patch_exception(0x1e0, exc_instruction_tlb_miss_e6500_book3e);
                break;
#endif
        }
        pr_info("MMU: Book3E HW tablewalk %s\n",
                book3e_htw_mode != PPC_HTW_NONE ? "enabled" : "not supported");
}

/*
 * Early initialization of the MMU TLB code
 */
static void early_init_this_mmu(void)
{
        unsigned int mas4;

        /* Set MAS4 based on page table setting */

        mas4 = 0x4 << MAS4_WIMGED_SHIFT;
        switch (book3e_htw_mode) {
        case PPC_HTW_E6500:
                mas4 |= MAS4_INDD;
                mas4 |= BOOK3E_PAGESZ_2M << MAS4_TSIZED_SHIFT;
                mas4 |= MAS4_TLBSELD(1);
                mmu_pte_psize = MMU_PAGE_2M;
                break;

        case PPC_HTW_IBM:
                mas4 |= MAS4_INDD;
#ifdef CONFIG_PPC_64K_PAGES
                mas4 |= BOOK3E_PAGESZ_256M << MAS4_TSIZED_SHIFT;
                mmu_pte_psize = MMU_PAGE_256M;
#else
                mas4 |= BOOK3E_PAGESZ_1M << MAS4_TSIZED_SHIFT;
                mmu_pte_psize = MMU_PAGE_1M;
#endif
                break;

        case PPC_HTW_NONE:
#ifdef CONFIG_PPC_64K_PAGES
                mas4 |= BOOK3E_PAGESZ_64K << MAS4_TSIZED_SHIFT;
#else
                mas4 |= BOOK3E_PAGESZ_4K << MAS4_TSIZED_SHIFT;
#endif
                mmu_pte_psize = mmu_virtual_psize;
                break;
        }
        mtspr(SPRN_MAS4, mas4);

#ifdef CONFIG_PPC_FSL_BOOK3E
        if (mmu_has_feature(MMU_FTR_TYPE_FSL_E)) {
                unsigned int num_cams;
                int __maybe_unused cpu = smp_processor_id();
                bool map = true;

                /* use a quarter of the TLBCAM for bolted linear map */
                num_cams = (mfspr(SPRN_TLB1CFG) & TLBnCFG_N_ENTRY) / 4;

                /*
                 * Only do the mapping once per core, or else the
                 * transient mapping would cause problems.
                 */
#ifdef CONFIG_SMP
                if (hweight32(get_tensr()) > 1)
                        map = false;
#endif

                if (map)
                        linear_map_top = map_mem_in_cams(linear_map_top,
                                                         num_cams, false);
        }
#endif

        /* A sync won't hurt us after mucking around with
         * the MMU configuration
         */
        mb();
}

static void __init early_init_mmu_global(void)
{
        /* XXX This will have to be decided at runtime, but right
         * now our boot and TLB miss code hard wires it. Ideally
         * we should find out a suitable page size and patch the
         * TLB miss code (either that or use the PACA to store
         * the value we want)
         */
        mmu_linear_psize = MMU_PAGE_1G;

        /* XXX This should be decided at runtime based on supported
         * page sizes in the TLB, but for now let's assume 16M is
         * always there and a good fit (which it probably is)
         *
         * Freescale booke only supports 4K pages in TLB0, so use that.
         */
        if (mmu_has_feature(MMU_FTR_TYPE_FSL_E))
                mmu_vmemmap_psize = MMU_PAGE_4K;
        else
                mmu_vmemmap_psize = MMU_PAGE_16M;

        /* XXX This code only checks for TLB 0 capabilities and doesn't
         *     check what page size combos are supported by the HW. It
         *     also doesn't handle the case where a separate array holds
         *     the IND entries from the array loaded by the PT.
         */
        /* Look for supported page sizes */
        setup_page_sizes();

        /* Look for HW tablewalk support */
        setup_mmu_htw();

#ifdef CONFIG_PPC_FSL_BOOK3E
        if (mmu_has_feature(MMU_FTR_TYPE_FSL_E)) {
                if (book3e_htw_mode == PPC_HTW_NONE) {
                        extlb_level_exc = EX_TLB_SIZE;
                        patch_exception(0x1c0, exc_data_tlb_miss_bolted_book3e);
                        patch_exception(0x1e0,
                                exc_instruction_tlb_miss_bolted_book3e);
                }
        }
#endif

        /* Set the global containing the top of the linear mapping
         * for use by the TLB miss code
         */
        linear_map_top = memblock_end_of_DRAM();
}

static void __init early_mmu_set_memory_limit(void)
{
#ifdef CONFIG_PPC_FSL_BOOK3E
        if (mmu_has_feature(MMU_FTR_TYPE_FSL_E)) {
                /*
                 * Limit memory so we dont have linear faults.
                 * Unlike memblock_set_current_limit, which limits
                 * memory available during early boot, this permanently
                 * reduces the memory available to Linux.  We need to
                 * do this because highmem is not supported on 64-bit.
                 */
                memblock_enforce_memory_limit(linear_map_top);
        }
#endif

        memblock_set_current_limit(linear_map_top);
}

/* boot cpu only */
void __init early_init_mmu(void)
{
        early_init_mmu_global();
        early_init_this_mmu();
        early_mmu_set_memory_limit();
}

void early_init_mmu_secondary(void)
{
        early_init_this_mmu();
}

void setup_initial_memory_limit(phys_addr_t first_memblock_base,
                                phys_addr_t first_memblock_size)
{
        /* On non-FSL Embedded 64-bit, we adjust the RMA size to match
         * the bolted TLB entry. We know for now that only 1G
         * entries are supported though that may eventually
         * change.
         *
         * on FSL Embedded 64-bit, usually all RAM is bolted, but with
         * unusual memory sizes it's possible for some RAM to not be mapped
         * (such RAM is not used at all by Linux, since we don't support
         * highmem on 64-bit).  We limit ppc64_rma_size to what would be
         * mappable if this memblock is the only one.  Additional memblocks
         * can only increase, not decrease, the amount that ends up getting
         * mapped.  We still limit max to 1G even if we'll eventually map
         * more.  This is due to what the early init code is set up to do.
         *
         * We crop it to the size of the first MEMBLOCK to
         * avoid going over total available memory just in case...
         */
#ifdef CONFIG_PPC_FSL_BOOK3E
        if (early_mmu_has_feature(MMU_FTR_TYPE_FSL_E)) {
                unsigned long linear_sz;
                unsigned int num_cams;

                /* use a quarter of the TLBCAM for bolted linear map */
                num_cams = (mfspr(SPRN_TLB1CFG) & TLBnCFG_N_ENTRY) / 4;

                linear_sz = map_mem_in_cams(first_memblock_size, num_cams,
                                            true);

                ppc64_rma_size = min_t(u64, linear_sz, 0x40000000);
        } else
#endif
                ppc64_rma_size = min_t(u64, first_memblock_size, 0x40000000);

        /* Finally limit subsequent allocations */
        memblock_set_current_limit(first_memblock_base + ppc64_rma_size);
}
#else /* ! CONFIG_PPC64 */
void __init early_init_mmu(void)
{
#ifdef CONFIG_PPC_47x
        early_init_mmu_47x();
#endif
}
#endif /* CONFIG_PPC64 */