Linux 4.18.8

[linux/fpc-iii.git] / arch / powerpc / mm / pgtable-radix.c

/*
 * Page table handling routines for radix page table.
 *
 * Copyright 2015-2016, Aneesh Kumar K.V, IBM Corporation.
 *
 * 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.
 */

#define pr_fmt(fmt) "radix-mmu: " fmt

#include <linux/kernel.h>
#include <linux/sched/mm.h>
#include <linux/memblock.h>
#include <linux/of_fdt.h>
#include <linux/mm.h>
#include <linux/string_helpers.h>
#include <linux/stop_machine.h>

#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/mmu_context.h>
#include <asm/dma.h>
#include <asm/machdep.h>
#include <asm/mmu.h>
#include <asm/firmware.h>
#include <asm/powernv.h>
#include <asm/sections.h>
#include <asm/trace.h>

#include <trace/events/thp.h>

unsigned int mmu_pid_bits;
unsigned int mmu_base_pid;

static int native_register_process_table(unsigned long base, unsigned long pg_sz,
                                         unsigned long table_size)
{
        unsigned long patb0, patb1;

        patb0 = be64_to_cpu(partition_tb[0].patb0);
        patb1 = base | table_size | PATB_GR;

        mmu_partition_table_set_entry(0, patb0, patb1);

        return 0;
}

static __ref void *early_alloc_pgtable(unsigned long size, int nid,
                        unsigned long region_start, unsigned long region_end)
{
        unsigned long pa = 0;
        void *pt;

        if (region_start || region_end) /* has region hint */
                pa = memblock_alloc_range(size, size, region_start, region_end,
                                                MEMBLOCK_NONE);
        else if (nid != -1) /* has node hint */
                pa = memblock_alloc_base_nid(size, size,
                                                MEMBLOCK_ALLOC_ANYWHERE,
                                                nid, MEMBLOCK_NONE);

        if (!pa)
                pa = memblock_alloc_base(size, size, MEMBLOCK_ALLOC_ANYWHERE);

        BUG_ON(!pa);

        pt = __va(pa);
        memset(pt, 0, size);

        return pt;
}

static int early_map_kernel_page(unsigned long ea, unsigned long pa,
                          pgprot_t flags,
                          unsigned int map_page_size,
                          int nid,
                          unsigned long region_start, unsigned long region_end)
{
        unsigned long pfn = pa >> PAGE_SHIFT;
        pgd_t *pgdp;
        pud_t *pudp;
        pmd_t *pmdp;
        pte_t *ptep;

        pgdp = pgd_offset_k(ea);
        if (pgd_none(*pgdp)) {
                pudp = early_alloc_pgtable(PUD_TABLE_SIZE, nid,
                                                region_start, region_end);
                pgd_populate(&init_mm, pgdp, pudp);
        }
        pudp = pud_offset(pgdp, ea);
        if (map_page_size == PUD_SIZE) {
                ptep = (pte_t *)pudp;
                goto set_the_pte;
        }
        if (pud_none(*pudp)) {
                pmdp = early_alloc_pgtable(PMD_TABLE_SIZE, nid,
                                                region_start, region_end);
                pud_populate(&init_mm, pudp, pmdp);
        }
        pmdp = pmd_offset(pudp, ea);
        if (map_page_size == PMD_SIZE) {
                ptep = pmdp_ptep(pmdp);
                goto set_the_pte;
        }
        if (!pmd_present(*pmdp)) {
                ptep = early_alloc_pgtable(PAGE_SIZE, nid,
                                                region_start, region_end);
                pmd_populate_kernel(&init_mm, pmdp, ptep);
        }
        ptep = pte_offset_kernel(pmdp, ea);

set_the_pte:
        set_pte_at(&init_mm, ea, ptep, pfn_pte(pfn, flags));
        smp_wmb();
        return 0;
}

/*
 * nid, region_start, and region_end are hints to try to place the page
 * table memory in the same node or region.
 */
static int __map_kernel_page(unsigned long ea, unsigned long pa,
                          pgprot_t flags,
                          unsigned int map_page_size,
                          int nid,
                          unsigned long region_start, unsigned long region_end)
{
        unsigned long pfn = pa >> PAGE_SHIFT;
        pgd_t *pgdp;
        pud_t *pudp;
        pmd_t *pmdp;
        pte_t *ptep;
        /*
         * Make sure task size is correct as per the max adddr
         */
        BUILD_BUG_ON(TASK_SIZE_USER64 > RADIX_PGTABLE_RANGE);

        if (unlikely(!slab_is_available()))
                return early_map_kernel_page(ea, pa, flags, map_page_size,
                                                nid, region_start, region_end);

        /*
         * Should make page table allocation functions be able to take a
         * node, so we can place kernel page tables on the right nodes after
         * boot.
         */
        pgdp = pgd_offset_k(ea);
        pudp = pud_alloc(&init_mm, pgdp, ea);
        if (!pudp)
                return -ENOMEM;
        if (map_page_size == PUD_SIZE) {
                ptep = (pte_t *)pudp;
                goto set_the_pte;
        }
        pmdp = pmd_alloc(&init_mm, pudp, ea);
        if (!pmdp)
                return -ENOMEM;
        if (map_page_size == PMD_SIZE) {
                ptep = pmdp_ptep(pmdp);
                goto set_the_pte;
        }
        ptep = pte_alloc_kernel(pmdp, ea);
        if (!ptep)
                return -ENOMEM;

set_the_pte:
        set_pte_at(&init_mm, ea, ptep, pfn_pte(pfn, flags));
        smp_wmb();
        return 0;
}

int radix__map_kernel_page(unsigned long ea, unsigned long pa,
                          pgprot_t flags,
                          unsigned int map_page_size)
{
        return __map_kernel_page(ea, pa, flags, map_page_size, -1, 0, 0);
}

#ifdef CONFIG_STRICT_KERNEL_RWX
void radix__change_memory_range(unsigned long start, unsigned long end,
                                unsigned long clear)
{
        unsigned long idx;
        pgd_t *pgdp;
        pud_t *pudp;
        pmd_t *pmdp;
        pte_t *ptep;

        start = ALIGN_DOWN(start, PAGE_SIZE);
        end = PAGE_ALIGN(end); // aligns up

        pr_debug("Changing flags on range %lx-%lx removing 0x%lx\n",
                 start, end, clear);

        for (idx = start; idx < end; idx += PAGE_SIZE) {
                pgdp = pgd_offset_k(idx);
                pudp = pud_alloc(&init_mm, pgdp, idx);
                if (!pudp)
                        continue;
                if (pud_huge(*pudp)) {
                        ptep = (pte_t *)pudp;
                        goto update_the_pte;
                }
                pmdp = pmd_alloc(&init_mm, pudp, idx);
                if (!pmdp)
                        continue;
                if (pmd_huge(*pmdp)) {
                        ptep = pmdp_ptep(pmdp);
                        goto update_the_pte;
                }
                ptep = pte_alloc_kernel(pmdp, idx);
                if (!ptep)
                        continue;
update_the_pte:
                radix__pte_update(&init_mm, idx, ptep, clear, 0, 0);
        }

        radix__flush_tlb_kernel_range(start, end);
}

void radix__mark_rodata_ro(void)
{
        unsigned long start, end;

        /*
         * mark_rodata_ro() will mark itself as !writable at some point.
         * Due to DD1 workaround in radix__pte_update(), we'll end up with
         * an invalid pte and the system will crash quite severly.
         */
        if (cpu_has_feature(CPU_FTR_POWER9_DD1)) {
                pr_warn("Warning: Unable to mark rodata read only on P9 DD1\n");
                return;
        }

        start = (unsigned long)_stext;
        end = (unsigned long)__init_begin;

        radix__change_memory_range(start, end, _PAGE_WRITE);
}

void radix__mark_initmem_nx(void)
{
        unsigned long start = (unsigned long)__init_begin;
        unsigned long end = (unsigned long)__init_end;

        radix__change_memory_range(start, end, _PAGE_EXEC);
}
#endif /* CONFIG_STRICT_KERNEL_RWX */

static inline void __meminit print_mapping(unsigned long start,
                                           unsigned long end,
                                           unsigned long size)
{
        char buf[10];

        if (end <= start)
                return;

        string_get_size(size, 1, STRING_UNITS_2, buf, sizeof(buf));

        pr_info("Mapped 0x%016lx-0x%016lx with %s pages\n", start, end, buf);
}

static int __meminit create_physical_mapping(unsigned long start,
                                             unsigned long end,
                                             int nid)
{
        unsigned long vaddr, addr, mapping_size = 0;
        pgprot_t prot;
        unsigned long max_mapping_size;
#ifdef CONFIG_STRICT_KERNEL_RWX
        int split_text_mapping = 1;
#else
        int split_text_mapping = 0;
#endif

        start = _ALIGN_UP(start, PAGE_SIZE);
        for (addr = start; addr < end; addr += mapping_size) {
                unsigned long gap, previous_size;
                int rc;

                gap = end - addr;
                previous_size = mapping_size;
                max_mapping_size = PUD_SIZE;

retry:
                if (IS_ALIGNED(addr, PUD_SIZE) && gap >= PUD_SIZE &&
                    mmu_psize_defs[MMU_PAGE_1G].shift &&
                    PUD_SIZE <= max_mapping_size)
                        mapping_size = PUD_SIZE;
                else if (IS_ALIGNED(addr, PMD_SIZE) && gap >= PMD_SIZE &&
                         mmu_psize_defs[MMU_PAGE_2M].shift)
                        mapping_size = PMD_SIZE;
                else
                        mapping_size = PAGE_SIZE;

                if (split_text_mapping && (mapping_size == PUD_SIZE) &&
                        (addr <= __pa_symbol(__init_begin)) &&
                        (addr + mapping_size) >= __pa_symbol(_stext)) {
                        max_mapping_size = PMD_SIZE;
                        goto retry;
                }

                if (split_text_mapping && (mapping_size == PMD_SIZE) &&
                    (addr <= __pa_symbol(__init_begin)) &&
                    (addr + mapping_size) >= __pa_symbol(_stext))
                        mapping_size = PAGE_SIZE;

                if (mapping_size != previous_size) {
                        print_mapping(start, addr, previous_size);
                        start = addr;
                }

                vaddr = (unsigned long)__va(addr);

                if (overlaps_kernel_text(vaddr, vaddr + mapping_size) ||
                    overlaps_interrupt_vector_text(vaddr, vaddr + mapping_size))
                        prot = PAGE_KERNEL_X;
                else
                        prot = PAGE_KERNEL;

                rc = __map_kernel_page(vaddr, addr, prot, mapping_size, nid, start, end);
                if (rc)
                        return rc;
        }

        print_mapping(start, addr, mapping_size);
        return 0;
}

void __init radix_init_pgtable(void)
{
        unsigned long rts_field;
        struct memblock_region *reg;

        /* We don't support slb for radix */
        mmu_slb_size = 0;
        /*
         * Create the linear mapping, using standard page size for now
         */
        for_each_memblock(memory, reg) {
                /*
                 * The memblock allocator  is up at this point, so the
                 * page tables will be allocated within the range. No
                 * need or a node (which we don't have yet).
                 */
                WARN_ON(create_physical_mapping(reg->base,
                                                reg->base + reg->size,
                                                -1));
        }

        /* Find out how many PID bits are supported */
        if (cpu_has_feature(CPU_FTR_HVMODE)) {
                if (!mmu_pid_bits)
                        mmu_pid_bits = 20;
#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
                /*
                 * When KVM is possible, we only use the top half of the
                 * PID space to avoid collisions between host and guest PIDs
                 * which can cause problems due to prefetch when exiting the
                 * guest with AIL=3
                 */
                mmu_base_pid = 1 << (mmu_pid_bits - 1);
#else
                mmu_base_pid = 1;
#endif
        } else {
                /* The guest uses the bottom half of the PID space */
                if (!mmu_pid_bits)
                        mmu_pid_bits = 19;
                mmu_base_pid = 1;
        }

        /*
         * Allocate Partition table and process table for the
         * host.
         */
        BUG_ON(PRTB_SIZE_SHIFT > 36);
        process_tb = early_alloc_pgtable(1UL << PRTB_SIZE_SHIFT, -1, 0, 0);
        /*
         * Fill in the process table.
         */
        rts_field = radix__get_tree_size();
        process_tb->prtb0 = cpu_to_be64(rts_field | __pa(init_mm.pgd) | RADIX_PGD_INDEX_SIZE);
        /*
         * Fill in the partition table. We are suppose to use effective address
         * of process table here. But our linear mapping also enable us to use
         * physical address here.
         */
        register_process_table(__pa(process_tb), 0, PRTB_SIZE_SHIFT - 12);
        pr_info("Process table %p and radix root for kernel: %p\n", process_tb, init_mm.pgd);
        asm volatile("ptesync" : : : "memory");
        asm volatile(PPC_TLBIE_5(%0,%1,2,1,1) : :
                     "r" (TLBIEL_INVAL_SET_LPID), "r" (0));
        asm volatile("eieio; tlbsync; ptesync" : : : "memory");
        trace_tlbie(0, 0, TLBIEL_INVAL_SET_LPID, 0, 2, 1, 1);

        /*
         * The init_mm context is given the first available (non-zero) PID,
         * which is the "guard PID" and contains no page table. PIDR should
         * never be set to zero because that duplicates the kernel address
         * space at the 0x0... offset (quadrant 0)!
         *
         * An arbitrary PID that may later be allocated by the PID allocator
         * for userspace processes must not be used either, because that
         * would cause stale user mappings for that PID on CPUs outside of
         * the TLB invalidation scheme (because it won't be in mm_cpumask).
         *
         * So permanently carve out one PID for the purpose of a guard PID.
         */
        init_mm.context.id = mmu_base_pid;
        mmu_base_pid++;
}

static void __init radix_init_partition_table(void)
{
        unsigned long rts_field, dw0;

        mmu_partition_table_init();
        rts_field = radix__get_tree_size();
        dw0 = rts_field | __pa(init_mm.pgd) | RADIX_PGD_INDEX_SIZE | PATB_HR;
        mmu_partition_table_set_entry(0, dw0, 0);

        pr_info("Initializing Radix MMU\n");
        pr_info("Partition table %p\n", partition_tb);
}

void __init radix_init_native(void)
{
        register_process_table = native_register_process_table;
}

static int __init get_idx_from_shift(unsigned int shift)
{
        int idx = -1;

        switch (shift) {
        case 0xc:
                idx = MMU_PAGE_4K;
                break;
        case 0x10:
                idx = MMU_PAGE_64K;
                break;
        case 0x15:
                idx = MMU_PAGE_2M;
                break;
        case 0x1e:
                idx = MMU_PAGE_1G;
                break;
        }
        return idx;
}

static int __init radix_dt_scan_page_sizes(unsigned long node,
                                           const char *uname, int depth,
                                           void *data)
{
        int size = 0;
        int shift, idx;
        unsigned int ap;
        const __be32 *prop;
        const char *type = of_get_flat_dt_prop(node, "device_type", NULL);

        /* We are scanning "cpu" nodes only */
        if (type == NULL || strcmp(type, "cpu") != 0)
                return 0;

        /* Find MMU PID size */
        prop = of_get_flat_dt_prop(node, "ibm,mmu-pid-bits", &size);
        if (prop && size == 4)
                mmu_pid_bits = be32_to_cpup(prop);

        /* Grab page size encodings */
        prop = of_get_flat_dt_prop(node, "ibm,processor-radix-AP-encodings", &size);
        if (!prop)
                return 0;

        pr_info("Page sizes from device-tree:\n");
        for (; size >= 4; size -= 4, ++prop) {

                struct mmu_psize_def *def;

                /* top 3 bit is AP encoding */
                shift = be32_to_cpu(prop[0]) & ~(0xe << 28);
                ap = be32_to_cpu(prop[0]) >> 29;
                pr_info("Page size shift = %d AP=0x%x\n", shift, ap);

                idx = get_idx_from_shift(shift);
                if (idx < 0)
                        continue;

                def = &mmu_psize_defs[idx];
                def->shift = shift;
                def->ap  = ap;
        }

        /* needed ? */
        cur_cpu_spec->mmu_features &= ~MMU_FTR_NO_SLBIE_B;
        return 1;
}

void __init radix__early_init_devtree(void)
{
        int rc;

        /*
         * Try to find the available page sizes in the device-tree
         */
        rc = of_scan_flat_dt(radix_dt_scan_page_sizes, NULL);
        if (rc != 0)  /* Found */
                goto found;
        /*
         * let's assume we have page 4k and 64k support
         */
        mmu_psize_defs[MMU_PAGE_4K].shift = 12;
        mmu_psize_defs[MMU_PAGE_4K].ap = 0x0;

        mmu_psize_defs[MMU_PAGE_64K].shift = 16;
        mmu_psize_defs[MMU_PAGE_64K].ap = 0x5;
found:
#ifdef CONFIG_SPARSEMEM_VMEMMAP
        if (mmu_psize_defs[MMU_PAGE_2M].shift) {
                /*
                 * map vmemmap using 2M if available
                 */
                mmu_vmemmap_psize = MMU_PAGE_2M;
        }
#endif /* CONFIG_SPARSEMEM_VMEMMAP */
        return;
}

static void update_hid_for_radix(void)
{
        unsigned long hid0;
        unsigned long rb = 3UL << PPC_BITLSHIFT(53); /* IS = 3 */

        asm volatile("ptesync": : :"memory");
        /* prs = 0, ric = 2, rs = 0, r = 1 is = 3 */
        asm volatile(PPC_TLBIE_5(%0, %4, %3, %2, %1)
                     : : "r"(rb), "i"(1), "i"(0), "i"(2), "r"(0) : "memory");
        /* prs = 1, ric = 2, rs = 0, r = 1 is = 3 */
        asm volatile(PPC_TLBIE_5(%0, %4, %3, %2, %1)
                     : : "r"(rb), "i"(1), "i"(1), "i"(2), "r"(0) : "memory");
        asm volatile("eieio; tlbsync; ptesync; isync; slbia": : :"memory");
        trace_tlbie(0, 0, rb, 0, 2, 0, 1);
        trace_tlbie(0, 0, rb, 0, 2, 1, 1);

        /*
         * now switch the HID
         */
        hid0  = mfspr(SPRN_HID0);
        hid0 |= HID0_POWER9_RADIX;
        mtspr(SPRN_HID0, hid0);
        asm volatile("isync": : :"memory");

        /* Wait for it to happen */
        while (!(mfspr(SPRN_HID0) & HID0_POWER9_RADIX))
                cpu_relax();
}

static void radix_init_amor(void)
{
        /*
        * In HV mode, we init AMOR (Authority Mask Override Register) so that
        * the hypervisor and guest can setup IAMR (Instruction Authority Mask
        * Register), enable key 0 and set it to 1.
        *
        * AMOR = 0b1100 .... 0000 (Mask for key 0 is 11)
        */
        mtspr(SPRN_AMOR, (3ul << 62));
}

static void radix_init_iamr(void)
{
        unsigned long iamr;

        /*
         * The IAMR should set to 0 on DD1.
         */
        if (cpu_has_feature(CPU_FTR_POWER9_DD1))
                iamr = 0;
        else
                iamr = (1ul << 62);

        /*
         * Radix always uses key0 of the IAMR to determine if an access is
         * allowed. We set bit 0 (IBM bit 1) of key0, to prevent instruction
         * fetch.
         */
        mtspr(SPRN_IAMR, iamr);
}

void __init radix__early_init_mmu(void)
{
        unsigned long lpcr;

#ifdef CONFIG_PPC_64K_PAGES
        /* PAGE_SIZE mappings */
        mmu_virtual_psize = MMU_PAGE_64K;
#else
        mmu_virtual_psize = MMU_PAGE_4K;
#endif

#ifdef CONFIG_SPARSEMEM_VMEMMAP
        /* vmemmap mapping */
        mmu_vmemmap_psize = mmu_virtual_psize;
#endif
        /*
         * initialize page table size
         */
        __pte_index_size = RADIX_PTE_INDEX_SIZE;
        __pmd_index_size = RADIX_PMD_INDEX_SIZE;
        __pud_index_size = RADIX_PUD_INDEX_SIZE;
        __pgd_index_size = RADIX_PGD_INDEX_SIZE;
        __pud_cache_index = RADIX_PUD_INDEX_SIZE;
        __pte_table_size = RADIX_PTE_TABLE_SIZE;
        __pmd_table_size = RADIX_PMD_TABLE_SIZE;
        __pud_table_size = RADIX_PUD_TABLE_SIZE;
        __pgd_table_size = RADIX_PGD_TABLE_SIZE;

        __pmd_val_bits = RADIX_PMD_VAL_BITS;
        __pud_val_bits = RADIX_PUD_VAL_BITS;
        __pgd_val_bits = RADIX_PGD_VAL_BITS;

        __kernel_virt_start = RADIX_KERN_VIRT_START;
        __kernel_virt_size = RADIX_KERN_VIRT_SIZE;
        __vmalloc_start = RADIX_VMALLOC_START;
        __vmalloc_end = RADIX_VMALLOC_END;
        __kernel_io_start = RADIX_KERN_IO_START;
        vmemmap = (struct page *)RADIX_VMEMMAP_BASE;
        ioremap_bot = IOREMAP_BASE;

#ifdef CONFIG_PCI
        pci_io_base = ISA_IO_BASE;
#endif
        __pte_frag_nr = RADIX_PTE_FRAG_NR;
        __pte_frag_size_shift = RADIX_PTE_FRAG_SIZE_SHIFT;
        __pmd_frag_nr = RADIX_PMD_FRAG_NR;
        __pmd_frag_size_shift = RADIX_PMD_FRAG_SIZE_SHIFT;

        if (!firmware_has_feature(FW_FEATURE_LPAR)) {
                radix_init_native();
                if (cpu_has_feature(CPU_FTR_POWER9_DD1))
                        update_hid_for_radix();
                lpcr = mfspr(SPRN_LPCR);
                mtspr(SPRN_LPCR, lpcr | LPCR_UPRT | LPCR_HR);
                radix_init_partition_table();
                radix_init_amor();
        } else {
                radix_init_pseries();
        }

        memblock_set_current_limit(MEMBLOCK_ALLOC_ANYWHERE);

        radix_init_iamr();
        radix_init_pgtable();
        /* Switch to the guard PID before turning on MMU */
        radix__switch_mmu_context(NULL, &init_mm);
        if (cpu_has_feature(CPU_FTR_HVMODE))
                tlbiel_all();
}

void radix__early_init_mmu_secondary(void)
{
        unsigned long lpcr;
        /*
         * update partition table control register and UPRT
         */
        if (!firmware_has_feature(FW_FEATURE_LPAR)) {

                if (cpu_has_feature(CPU_FTR_POWER9_DD1))
                        update_hid_for_radix();

                lpcr = mfspr(SPRN_LPCR);
                mtspr(SPRN_LPCR, lpcr | LPCR_UPRT | LPCR_HR);

                mtspr(SPRN_PTCR,
                      __pa(partition_tb) | (PATB_SIZE_SHIFT - 12));
                radix_init_amor();
        }
        radix_init_iamr();

        radix__switch_mmu_context(NULL, &init_mm);
        if (cpu_has_feature(CPU_FTR_HVMODE))
                tlbiel_all();
}

void radix__mmu_cleanup_all(void)
{
        unsigned long lpcr;

        if (!firmware_has_feature(FW_FEATURE_LPAR)) {
                lpcr = mfspr(SPRN_LPCR);
                mtspr(SPRN_LPCR, lpcr & ~LPCR_UPRT);
                mtspr(SPRN_PTCR, 0);
                powernv_set_nmmu_ptcr(0);
                radix__flush_tlb_all();
        }
}

void radix__setup_initial_memory_limit(phys_addr_t first_memblock_base,
                                phys_addr_t first_memblock_size)
{
        /* We don't currently support the first MEMBLOCK not mapping 0
         * physical on those processors
         */
        BUG_ON(first_memblock_base != 0);

        /*
         * Radix mode is not limited by RMA / VRMA addressing.
         */
        ppc64_rma_size = ULONG_MAX;
}

#ifdef CONFIG_MEMORY_HOTPLUG
static void free_pte_table(pte_t *pte_start, pmd_t *pmd)
{
        pte_t *pte;
        int i;

        for (i = 0; i < PTRS_PER_PTE; i++) {
                pte = pte_start + i;
                if (!pte_none(*pte))
                        return;
        }

        pte_free_kernel(&init_mm, pte_start);
        pmd_clear(pmd);
}

static void free_pmd_table(pmd_t *pmd_start, pud_t *pud)
{
        pmd_t *pmd;
        int i;

        for (i = 0; i < PTRS_PER_PMD; i++) {
                pmd = pmd_start + i;
                if (!pmd_none(*pmd))
                        return;
        }

        pmd_free(&init_mm, pmd_start);
        pud_clear(pud);
}

struct change_mapping_params {
        pte_t *pte;
        unsigned long start;
        unsigned long end;
        unsigned long aligned_start;
        unsigned long aligned_end;
};

static int __meminit stop_machine_change_mapping(void *data)
{
        struct change_mapping_params *params =
                        (struct change_mapping_params *)data;

        if (!data)
                return -1;

        spin_unlock(&init_mm.page_table_lock);
        pte_clear(&init_mm, params->aligned_start, params->pte);
        create_physical_mapping(params->aligned_start, params->start, -1);
        create_physical_mapping(params->end, params->aligned_end, -1);
        spin_lock(&init_mm.page_table_lock);
        return 0;
}

static void remove_pte_table(pte_t *pte_start, unsigned long addr,
                             unsigned long end)
{
        unsigned long next;
        pte_t *pte;

        pte = pte_start + pte_index(addr);
        for (; addr < end; addr = next, pte++) {
                next = (addr + PAGE_SIZE) & PAGE_MASK;
                if (next > end)
                        next = end;

                if (!pte_present(*pte))
                        continue;

                if (!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(next)) {
                        /*
                         * The vmemmap_free() and remove_section_mapping()
                         * codepaths call us with aligned addresses.
                         */
                        WARN_ONCE(1, "%s: unaligned range\n", __func__);
                        continue;
                }

                pte_clear(&init_mm, addr, pte);
        }
}

/*
 * clear the pte and potentially split the mapping helper
 */
static void __meminit split_kernel_mapping(unsigned long addr, unsigned long end,
                                unsigned long size, pte_t *pte)
{
        unsigned long mask = ~(size - 1);
        unsigned long aligned_start = addr & mask;
        unsigned long aligned_end = addr + size;
        struct change_mapping_params params;
        bool split_region = false;

        if ((end - addr) < size) {
                /*
                 * We're going to clear the PTE, but not flushed
                 * the mapping, time to remap and flush. The
                 * effects if visible outside the processor or
                 * if we are running in code close to the
                 * mapping we cleared, we are in trouble.
                 */
                if (overlaps_kernel_text(aligned_start, addr) ||
                        overlaps_kernel_text(end, aligned_end)) {
                        /*
                         * Hack, just return, don't pte_clear
                         */
                        WARN_ONCE(1, "Linear mapping %lx->%lx overlaps kernel "
                                  "text, not splitting\n", addr, end);
                        return;
                }
                split_region = true;
        }

        if (split_region) {
                params.pte = pte;
                params.start = addr;
                params.end = end;
                params.aligned_start = addr & ~(size - 1);
                params.aligned_end = min_t(unsigned long, aligned_end,
                                (unsigned long)__va(memblock_end_of_DRAM()));
                stop_machine(stop_machine_change_mapping, &params, NULL);
                return;
        }

        pte_clear(&init_mm, addr, pte);
}

static void remove_pmd_table(pmd_t *pmd_start, unsigned long addr,
                             unsigned long end)
{
        unsigned long next;
        pte_t *pte_base;
        pmd_t *pmd;

        pmd = pmd_start + pmd_index(addr);
        for (; addr < end; addr = next, pmd++) {
                next = pmd_addr_end(addr, end);

                if (!pmd_present(*pmd))
                        continue;

                if (pmd_huge(*pmd)) {
                        split_kernel_mapping(addr, end, PMD_SIZE, (pte_t *)pmd);
                        continue;
                }

                pte_base = (pte_t *)pmd_page_vaddr(*pmd);
                remove_pte_table(pte_base, addr, next);
                free_pte_table(pte_base, pmd);
        }
}

static void remove_pud_table(pud_t *pud_start, unsigned long addr,
                             unsigned long end)
{
        unsigned long next;
        pmd_t *pmd_base;
        pud_t *pud;

        pud = pud_start + pud_index(addr);
        for (; addr < end; addr = next, pud++) {
                next = pud_addr_end(addr, end);

                if (!pud_present(*pud))
                        continue;

                if (pud_huge(*pud)) {
                        split_kernel_mapping(addr, end, PUD_SIZE, (pte_t *)pud);
                        continue;
                }

                pmd_base = (pmd_t *)pud_page_vaddr(*pud);
                remove_pmd_table(pmd_base, addr, next);
                free_pmd_table(pmd_base, pud);
        }
}

static void __meminit remove_pagetable(unsigned long start, unsigned long end)
{
        unsigned long addr, next;
        pud_t *pud_base;
        pgd_t *pgd;

        spin_lock(&init_mm.page_table_lock);

        for (addr = start; addr < end; addr = next) {
                next = pgd_addr_end(addr, end);

                pgd = pgd_offset_k(addr);
                if (!pgd_present(*pgd))
                        continue;

                if (pgd_huge(*pgd)) {
                        split_kernel_mapping(addr, end, PGDIR_SIZE, (pte_t *)pgd);
                        continue;
                }

                pud_base = (pud_t *)pgd_page_vaddr(*pgd);
                remove_pud_table(pud_base, addr, next);
        }

        spin_unlock(&init_mm.page_table_lock);
        radix__flush_tlb_kernel_range(start, end);
}

int __meminit radix__create_section_mapping(unsigned long start, unsigned long end, int nid)
{
        return create_physical_mapping(start, end, nid);
}

int __meminit radix__remove_section_mapping(unsigned long start, unsigned long end)
{
        remove_pagetable(start, end);
        return 0;
}
#endif /* CONFIG_MEMORY_HOTPLUG */

#ifdef CONFIG_SPARSEMEM_VMEMMAP
static int __map_kernel_page_nid(unsigned long ea, unsigned long pa,
                                 pgprot_t flags, unsigned int map_page_size,
                                 int nid)
{
        return __map_kernel_page(ea, pa, flags, map_page_size, nid, 0, 0);
}

int __meminit radix__vmemmap_create_mapping(unsigned long start,
                                      unsigned long page_size,
                                      unsigned long phys)
{
        /* Create a PTE encoding */
        unsigned long flags = _PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_KERNEL_RW;
        int nid = early_pfn_to_nid(phys >> PAGE_SHIFT);
        int ret;

        ret = __map_kernel_page_nid(start, phys, __pgprot(flags), page_size, nid);
        BUG_ON(ret);

        return 0;
}

#ifdef CONFIG_MEMORY_HOTPLUG
void __meminit radix__vmemmap_remove_mapping(unsigned long start, unsigned long page_size)
{
        remove_pagetable(start, start + page_size);
}
#endif
#endif

#ifdef CONFIG_TRANSPARENT_HUGEPAGE

unsigned long radix__pmd_hugepage_update(struct mm_struct *mm, unsigned long addr,
                                  pmd_t *pmdp, unsigned long clr,
                                  unsigned long set)
{
        unsigned long old;

#ifdef CONFIG_DEBUG_VM
        WARN_ON(!radix__pmd_trans_huge(*pmdp) && !pmd_devmap(*pmdp));
        assert_spin_locked(pmd_lockptr(mm, pmdp));
#endif

        old = radix__pte_update(mm, addr, (pte_t *)pmdp, clr, set, 1);
        trace_hugepage_update(addr, old, clr, set);

        return old;
}

pmd_t radix__pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address,
                        pmd_t *pmdp)

{
        pmd_t pmd;

        VM_BUG_ON(address & ~HPAGE_PMD_MASK);
        VM_BUG_ON(radix__pmd_trans_huge(*pmdp));
        VM_BUG_ON(pmd_devmap(*pmdp));
        /*
         * khugepaged calls this for normal pmd
         */
        pmd = *pmdp;
        pmd_clear(pmdp);

        /*FIXME!!  Verify whether we need this kick below */
        serialize_against_pte_lookup(vma->vm_mm);

        radix__flush_tlb_collapsed_pmd(vma->vm_mm, address);

        return pmd;
}

/*
 * For us pgtable_t is pte_t *. Inorder to save the deposisted
 * page table, we consider the allocated page table as a list
 * head. On withdraw we need to make sure we zero out the used
 * list_head memory area.
 */
void radix__pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
                                 pgtable_t pgtable)
{
        struct list_head *lh = (struct list_head *) pgtable;

        assert_spin_locked(pmd_lockptr(mm, pmdp));

        /* FIFO */
        if (!pmd_huge_pte(mm, pmdp))
                INIT_LIST_HEAD(lh);
        else
                list_add(lh, (struct list_head *) pmd_huge_pte(mm, pmdp));
        pmd_huge_pte(mm, pmdp) = pgtable;
}

pgtable_t radix__pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp)
{
        pte_t *ptep;
        pgtable_t pgtable;
        struct list_head *lh;

        assert_spin_locked(pmd_lockptr(mm, pmdp));

        /* FIFO */
        pgtable = pmd_huge_pte(mm, pmdp);
        lh = (struct list_head *) pgtable;
        if (list_empty(lh))
                pmd_huge_pte(mm, pmdp) = NULL;
        else {
                pmd_huge_pte(mm, pmdp) = (pgtable_t) lh->next;
                list_del(lh);
        }
        ptep = (pte_t *) pgtable;
        *ptep = __pte(0);
        ptep++;
        *ptep = __pte(0);
        return pgtable;
}


pmd_t radix__pmdp_huge_get_and_clear(struct mm_struct *mm,
                               unsigned long addr, pmd_t *pmdp)
{
        pmd_t old_pmd;
        unsigned long old;

        old = radix__pmd_hugepage_update(mm, addr, pmdp, ~0UL, 0);
        old_pmd = __pmd(old);
        /*
         * Serialize against find_current_mm_pte which does lock-less
         * lookup in page tables with local interrupts disabled. For huge pages
         * it casts pmd_t to pte_t. Since format of pte_t is different from
         * pmd_t we want to prevent transit from pmd pointing to page table
         * to pmd pointing to huge page (and back) while interrupts are disabled.
         * We clear pmd to possibly replace it with page table pointer in
         * different code paths. So make sure we wait for the parallel
         * find_current_mm_pte to finish.
         */
        serialize_against_pte_lookup(mm);
        return old_pmd;
}

int radix__has_transparent_hugepage(void)
{
        /* For radix 2M at PMD level means thp */
        if (mmu_psize_defs[MMU_PAGE_2M].shift == PMD_SHIFT)
                return 1;
        return 0;
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */

void radix__ptep_set_access_flags(struct vm_area_struct *vma, pte_t *ptep,
                                  pte_t entry, unsigned long address, int psize)
{
        struct mm_struct *mm = vma->vm_mm;
        unsigned long set = pte_val(entry) & (_PAGE_DIRTY | _PAGE_ACCESSED |
                                              _PAGE_RW | _PAGE_EXEC);
        /*
         * To avoid NMMU hang while relaxing access, we need mark
         * the pte invalid in between.
         */
        if (cpu_has_feature(CPU_FTR_POWER9_DD1) ||
            atomic_read(&mm->context.copros) > 0) {
                unsigned long old_pte, new_pte;

                old_pte = __radix_pte_update(ptep, ~0, 0);
                /*
                 * new value of pte
                 */
                new_pte = old_pte | set;
                radix__flush_tlb_page_psize(mm, address, psize);
                __radix_pte_update(ptep, 0, new_pte);
        } else {
                __radix_pte_update(ptep, 0, set);
                /*
                 * Book3S does not require a TLB flush when relaxing access
                 * restrictions when the address space is not attached to a
                 * NMMU, because the core MMU will reload the pte after taking
                 * an access fault, which is defined by the architectue.
                 */
        }
        /* See ptesync comment in radix__set_pte_at */
}