powerpc/tm: Fix null pointer deference in flush_hash_page

[deliverable/linux.git] / arch / powerpc / mm / hash_utils_64.c

/*
 * PowerPC64 port by Mike Corrigan and Dave Engebretsen
 *   {mikejc|engebret}@us.ibm.com
 *
 *    Copyright (c) 2000 Mike Corrigan <mikejc@us.ibm.com>
 *
 * SMP scalability work:
 *    Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM
 * 
 *    Module name: htab.c
 *
 *    Description:
 *      PowerPC Hashed Page Table functions
 *
 * 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.
 */

#undef DEBUG
#undef DEBUG_LOW

#include <linux/spinlock.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/sysctl.h>
#include <linux/export.h>
#include <linux/ctype.h>
#include <linux/cache.h>
#include <linux/init.h>
#include <linux/signal.h>
#include <linux/memblock.h>

#include <asm/processor.h>
#include <asm/pgtable.h>
#include <asm/mmu.h>
#include <asm/mmu_context.h>
#include <asm/page.h>
#include <asm/types.h>
#include <asm/uaccess.h>
#include <asm/machdep.h>
#include <asm/prom.h>
#include <asm/tlbflush.h>
#include <asm/io.h>
#include <asm/eeh.h>
#include <asm/tlb.h>
#include <asm/cacheflush.h>
#include <asm/cputable.h>
#include <asm/sections.h>
#include <asm/spu.h>
#include <asm/udbg.h>
#include <asm/code-patching.h>
#include <asm/fadump.h>
#include <asm/firmware.h>
#include <asm/tm.h>

#ifdef DEBUG
#define DBG(fmt...) udbg_printf(fmt)
#else
#define DBG(fmt...)
#endif

#ifdef DEBUG_LOW
#define DBG_LOW(fmt...) udbg_printf(fmt)
#else
#define DBG_LOW(fmt...)
#endif

#define KB (1024)
#define MB (1024*KB)
#define GB (1024L*MB)

/*
 * Note:  pte   --> Linux PTE
 *        HPTE  --> PowerPC Hashed Page Table Entry
 *
 * Execution context:
 *   htab_initialize is called with the MMU off (of course), but
 *   the kernel has been copied down to zero so it can directly
 *   reference global data.  At this point it is very difficult
 *   to print debug info.
 *
 */

#ifdef CONFIG_U3_DART
extern unsigned long dart_tablebase;
#endif /* CONFIG_U3_DART */

static unsigned long _SDR1;
struct mmu_psize_def mmu_psize_defs[MMU_PAGE_COUNT];

struct hash_pte *htab_address;
unsigned long htab_size_bytes;
unsigned long htab_hash_mask;
EXPORT_SYMBOL_GPL(htab_hash_mask);
int mmu_linear_psize = MMU_PAGE_4K;
int mmu_virtual_psize = MMU_PAGE_4K;
int mmu_vmalloc_psize = MMU_PAGE_4K;
#ifdef CONFIG_SPARSEMEM_VMEMMAP
int mmu_vmemmap_psize = MMU_PAGE_4K;
#endif
int mmu_io_psize = MMU_PAGE_4K;
int mmu_kernel_ssize = MMU_SEGSIZE_256M;
int mmu_highuser_ssize = MMU_SEGSIZE_256M;
u16 mmu_slb_size = 64;
EXPORT_SYMBOL_GPL(mmu_slb_size);
#ifdef CONFIG_PPC_64K_PAGES
int mmu_ci_restrictions;
#endif
#ifdef CONFIG_DEBUG_PAGEALLOC
static u8 *linear_map_hash_slots;
static unsigned long linear_map_hash_count;
static DEFINE_SPINLOCK(linear_map_hash_lock);
#endif /* CONFIG_DEBUG_PAGEALLOC */

/* There are definitions of page sizes arrays to be used when none
 * is provided by the firmware.
 */

/* Pre-POWER4 CPUs (4k pages only)
 */
static struct mmu_psize_def mmu_psize_defaults_old[] = {
        [MMU_PAGE_4K] = {
                .shift  = 12,
                .sllp   = 0,
                .penc   = {[MMU_PAGE_4K] = 0, [1 ... MMU_PAGE_COUNT - 1] = -1},
                .avpnm  = 0,
                .tlbiel = 0,
        },
};

/* POWER4, GPUL, POWER5
 *
 * Support for 16Mb large pages
 */
static struct mmu_psize_def mmu_psize_defaults_gp[] = {
        [MMU_PAGE_4K] = {
                .shift  = 12,
                .sllp   = 0,
                .penc   = {[MMU_PAGE_4K] = 0, [1 ... MMU_PAGE_COUNT - 1] = -1},
                .avpnm  = 0,
                .tlbiel = 1,
        },
        [MMU_PAGE_16M] = {
                .shift  = 24,
                .sllp   = SLB_VSID_L,
                .penc   = {[0 ... MMU_PAGE_16M - 1] = -1, [MMU_PAGE_16M] = 0,
                            [MMU_PAGE_16M + 1 ... MMU_PAGE_COUNT - 1] = -1 },
                .avpnm  = 0x1UL,
                .tlbiel = 0,
        },
};

static unsigned long htab_convert_pte_flags(unsigned long pteflags)
{
        unsigned long rflags = pteflags & 0x1fa;

        /* _PAGE_EXEC -> NOEXEC */
        if ((pteflags & _PAGE_EXEC) == 0)
                rflags |= HPTE_R_N;

        /* PP bits. PAGE_USER is already PP bit 0x2, so we only
         * need to add in 0x1 if it's a read-only user page
         */
        if ((pteflags & _PAGE_USER) && !((pteflags & _PAGE_RW) &&
                                         (pteflags & _PAGE_DIRTY)))
                rflags |= 1;

        /* Always add C */
        return rflags | HPTE_R_C;
}

int htab_bolt_mapping(unsigned long vstart, unsigned long vend,
                      unsigned long pstart, unsigned long prot,
                      int psize, int ssize)
{
        unsigned long vaddr, paddr;
        unsigned int step, shift;
        int ret = 0;

        shift = mmu_psize_defs[psize].shift;
        step = 1 << shift;

        prot = htab_convert_pte_flags(prot);

        DBG("htab_bolt_mapping(%lx..%lx -> %lx (%lx,%d,%d)\n",
            vstart, vend, pstart, prot, psize, ssize);

        for (vaddr = vstart, paddr = pstart; vaddr < vend;
             vaddr += step, paddr += step) {
                unsigned long hash, hpteg;
                unsigned long vsid = get_kernel_vsid(vaddr, ssize);
                unsigned long vpn  = hpt_vpn(vaddr, vsid, ssize);
                unsigned long tprot = prot;

                /*
                 * If we hit a bad address return error.
                 */
                if (!vsid)
                        return -1;
                /* Make kernel text executable */
                if (overlaps_kernel_text(vaddr, vaddr + step))
                        tprot &= ~HPTE_R_N;

                hash = hpt_hash(vpn, shift, ssize);
                hpteg = ((hash & htab_hash_mask) * HPTES_PER_GROUP);

                BUG_ON(!ppc_md.hpte_insert);
                ret = ppc_md.hpte_insert(hpteg, vpn, paddr, tprot,
                                         HPTE_V_BOLTED, psize, psize, ssize);

                if (ret < 0)
                        break;
#ifdef CONFIG_DEBUG_PAGEALLOC
                if ((paddr >> PAGE_SHIFT) < linear_map_hash_count)
                        linear_map_hash_slots[paddr >> PAGE_SHIFT] = ret | 0x80;
#endif /* CONFIG_DEBUG_PAGEALLOC */
        }
        return ret < 0 ? ret : 0;
}

#ifdef CONFIG_MEMORY_HOTPLUG
static int htab_remove_mapping(unsigned long vstart, unsigned long vend,
                      int psize, int ssize)
{
        unsigned long vaddr;
        unsigned int step, shift;

        shift = mmu_psize_defs[psize].shift;
        step = 1 << shift;

        if (!ppc_md.hpte_removebolted) {
                printk(KERN_WARNING "Platform doesn't implement "
                                "hpte_removebolted\n");
                return -EINVAL;
        }

        for (vaddr = vstart; vaddr < vend; vaddr += step)
                ppc_md.hpte_removebolted(vaddr, psize, ssize);

        return 0;
}
#endif /* CONFIG_MEMORY_HOTPLUG */

static int __init htab_dt_scan_seg_sizes(unsigned long node,
                                         const char *uname, int depth,
                                         void *data)
{
        char *type = of_get_flat_dt_prop(node, "device_type", NULL);
        u32 *prop;
        unsigned long size = 0;

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

        prop = (u32 *)of_get_flat_dt_prop(node, "ibm,processor-segment-sizes",
                                          &size);
        if (prop == NULL)
                return 0;
        for (; size >= 4; size -= 4, ++prop) {
                if (prop[0] == 40) {
                        DBG("1T segment support detected\n");
                        cur_cpu_spec->mmu_features |= MMU_FTR_1T_SEGMENT;
                        return 1;
                }
        }
        cur_cpu_spec->mmu_features &= ~MMU_FTR_NO_SLBIE_B;
        return 0;
}

static void __init htab_init_seg_sizes(void)
{
        of_scan_flat_dt(htab_dt_scan_seg_sizes, NULL);
}

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 0x14:
                idx = MMU_PAGE_1M;
                break;
        case 0x18:
                idx = MMU_PAGE_16M;
                break;
        case 0x22:
                idx = MMU_PAGE_16G;
                break;
        }
        return idx;
}

static int __init htab_dt_scan_page_sizes(unsigned long node,
                                          const char *uname, int depth,
                                          void *data)
{
        char *type = of_get_flat_dt_prop(node, "device_type", NULL);
        u32 *prop;
        unsigned long size = 0;

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

        prop = (u32 *)of_get_flat_dt_prop(node,
                                          "ibm,segment-page-sizes", &size);
        if (prop != NULL) {
                pr_info("Page sizes from device-tree:\n");
                size /= 4;
                cur_cpu_spec->mmu_features &= ~(MMU_FTR_16M_PAGE);
                while(size > 0) {
                        unsigned int base_shift = prop[0];
                        unsigned int slbenc = prop[1];
                        unsigned int lpnum = prop[2];
                        struct mmu_psize_def *def;
                        int idx, base_idx;

                        size -= 3; prop += 3;
                        base_idx = get_idx_from_shift(base_shift);
                        if (base_idx < 0) {
                                /*
                                 * skip the pte encoding also
                                 */
                                prop += lpnum * 2; size -= lpnum * 2;
                                continue;
                        }
                        def = &mmu_psize_defs[base_idx];
                        if (base_idx == MMU_PAGE_16M)
                                cur_cpu_spec->mmu_features |= MMU_FTR_16M_PAGE;

                        def->shift = base_shift;
                        if (base_shift <= 23)
                                def->avpnm = 0;
                        else
                                def->avpnm = (1 << (base_shift - 23)) - 1;
                        def->sllp = slbenc;
                        /*
                         * We don't know for sure what's up with tlbiel, so
                         * for now we only set it for 4K and 64K pages
                         */
                        if (base_idx == MMU_PAGE_4K || base_idx == MMU_PAGE_64K)
                                def->tlbiel = 1;
                        else
                                def->tlbiel = 0;

                        while (size > 0 && lpnum) {
                                unsigned int shift = prop[0];
                                int penc  = prop[1];

                                prop += 2; size -= 2;
                                lpnum--;

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

                                if (penc == -1)
                                        pr_err("Invalid penc for base_shift=%d "
                                               "shift=%d\n", base_shift, shift);

                                def->penc[idx] = penc;
                                pr_info("base_shift=%d: shift=%d, sllp=0x%04lx,"
                                        " avpnm=0x%08lx, tlbiel=%d, penc=%d\n",
                                        base_shift, shift, def->sllp,
                                        def->avpnm, def->tlbiel, def->penc[idx]);
                        }
                }
                return 1;
        }
        return 0;
}

#ifdef CONFIG_HUGETLB_PAGE
/* Scan for 16G memory blocks that have been set aside for huge pages
 * and reserve those blocks for 16G huge pages.
 */
static int __init htab_dt_scan_hugepage_blocks(unsigned long node,
                                        const char *uname, int depth,
                                        void *data) {
        char *type = of_get_flat_dt_prop(node, "device_type", NULL);
        unsigned long *addr_prop;
        u32 *page_count_prop;
        unsigned int expected_pages;
        long unsigned int phys_addr;
        long unsigned int block_size;

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

        /* This property is the log base 2 of the number of virtual pages that
         * will represent this memory block. */
        page_count_prop = of_get_flat_dt_prop(node, "ibm,expected#pages", NULL);
        if (page_count_prop == NULL)
                return 0;
        expected_pages = (1 << page_count_prop[0]);
        addr_prop = of_get_flat_dt_prop(node, "reg", NULL);
        if (addr_prop == NULL)
                return 0;
        phys_addr = addr_prop[0];
        block_size = addr_prop[1];
        if (block_size != (16 * GB))
                return 0;
        printk(KERN_INFO "Huge page(16GB) memory: "
                        "addr = 0x%lX size = 0x%lX pages = %d\n",
                        phys_addr, block_size, expected_pages);
        if (phys_addr + (16 * GB) <= memblock_end_of_DRAM()) {
                memblock_reserve(phys_addr, block_size * expected_pages);
                add_gpage(phys_addr, block_size, expected_pages);
        }
        return 0;
}
#endif /* CONFIG_HUGETLB_PAGE */

static void mmu_psize_set_default_penc(void)
{
        int bpsize, apsize;
        for (bpsize = 0; bpsize < MMU_PAGE_COUNT; bpsize++)
                for (apsize = 0; apsize < MMU_PAGE_COUNT; apsize++)
                        mmu_psize_defs[bpsize].penc[apsize] = -1;
}

static void __init htab_init_page_sizes(void)
{
        int rc;

        /* se the invalid penc to -1 */
        mmu_psize_set_default_penc();

        /* Default to 4K pages only */
        memcpy(mmu_psize_defs, mmu_psize_defaults_old,
               sizeof(mmu_psize_defaults_old));

        /*
         * Try to find the available page sizes in the device-tree
         */
        rc = of_scan_flat_dt(htab_dt_scan_page_sizes, NULL);
        if (rc != 0)  /* Found */
                goto found;

        /*
         * Not in the device-tree, let's fallback on known size
         * list for 16M capable GP & GR
         */
        if (mmu_has_feature(MMU_FTR_16M_PAGE))
                memcpy(mmu_psize_defs, mmu_psize_defaults_gp,
                       sizeof(mmu_psize_defaults_gp));
 found:
#ifndef CONFIG_DEBUG_PAGEALLOC
        /*
         * Pick a size for the linear mapping. Currently, we only support
         * 16M, 1M and 4K which is the default
         */
        if (mmu_psize_defs[MMU_PAGE_16M].shift)
                mmu_linear_psize = MMU_PAGE_16M;
        else if (mmu_psize_defs[MMU_PAGE_1M].shift)
                mmu_linear_psize = MMU_PAGE_1M;
#endif /* CONFIG_DEBUG_PAGEALLOC */

#ifdef CONFIG_PPC_64K_PAGES
        /*
         * Pick a size for the ordinary pages. Default is 4K, we support
         * 64K for user mappings and vmalloc if supported by the processor.
         * We only use 64k for ioremap if the processor
         * (and firmware) support cache-inhibited large pages.
         * If not, we use 4k and set mmu_ci_restrictions so that
         * hash_page knows to switch processes that use cache-inhibited
         * mappings to 4k pages.
         */
        if (mmu_psize_defs[MMU_PAGE_64K].shift) {
                mmu_virtual_psize = MMU_PAGE_64K;
                mmu_vmalloc_psize = MMU_PAGE_64K;
                if (mmu_linear_psize == MMU_PAGE_4K)
                        mmu_linear_psize = MMU_PAGE_64K;
                if (mmu_has_feature(MMU_FTR_CI_LARGE_PAGE)) {
                        /*
                         * Don't use 64k pages for ioremap on pSeries, since
                         * that would stop us accessing the HEA ethernet.
                         */
                        if (!machine_is(pseries))
                                mmu_io_psize = MMU_PAGE_64K;
                } else
                        mmu_ci_restrictions = 1;
        }
#endif /* CONFIG_PPC_64K_PAGES */

#ifdef CONFIG_SPARSEMEM_VMEMMAP
        /* We try to use 16M pages for vmemmap if that is supported
         * and we have at least 1G of RAM at boot
         */
        if (mmu_psize_defs[MMU_PAGE_16M].shift &&
            memblock_phys_mem_size() >= 0x40000000)
                mmu_vmemmap_psize = MMU_PAGE_16M;
        else if (mmu_psize_defs[MMU_PAGE_64K].shift)
                mmu_vmemmap_psize = MMU_PAGE_64K;
        else
                mmu_vmemmap_psize = MMU_PAGE_4K;
#endif /* CONFIG_SPARSEMEM_VMEMMAP */

        printk(KERN_DEBUG "Page orders: linear mapping = %d, "
               "virtual = %d, io = %d"
#ifdef CONFIG_SPARSEMEM_VMEMMAP
               ", vmemmap = %d"
#endif
               "\n",
               mmu_psize_defs[mmu_linear_psize].shift,
               mmu_psize_defs[mmu_virtual_psize].shift,
               mmu_psize_defs[mmu_io_psize].shift
#ifdef CONFIG_SPARSEMEM_VMEMMAP
               ,mmu_psize_defs[mmu_vmemmap_psize].shift
#endif
               );

#ifdef CONFIG_HUGETLB_PAGE
        /* Reserve 16G huge page memory sections for huge pages */
        of_scan_flat_dt(htab_dt_scan_hugepage_blocks, NULL);
#endif /* CONFIG_HUGETLB_PAGE */
}

static int __init htab_dt_scan_pftsize(unsigned long node,
                                       const char *uname, int depth,
                                       void *data)
{
        char *type = of_get_flat_dt_prop(node, "device_type", NULL);
        u32 *prop;

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

        prop = (u32 *)of_get_flat_dt_prop(node, "ibm,pft-size", NULL);
        if (prop != NULL) {
                /* pft_size[0] is the NUMA CEC cookie */
                ppc64_pft_size = prop[1];
                return 1;
        }
        return 0;
}

static unsigned long __init htab_get_table_size(void)
{
        unsigned long mem_size, rnd_mem_size, pteg_count, psize;

        /* If hash size isn't already provided by the platform, we try to
         * retrieve it from the device-tree. If it's not there neither, we
         * calculate it now based on the total RAM size
         */
        if (ppc64_pft_size == 0)
                of_scan_flat_dt(htab_dt_scan_pftsize, NULL);
        if (ppc64_pft_size)
                return 1UL << ppc64_pft_size;

        /* round mem_size up to next power of 2 */
        mem_size = memblock_phys_mem_size();
        rnd_mem_size = 1UL << __ilog2(mem_size);
        if (rnd_mem_size < mem_size)
                rnd_mem_size <<= 1;

        /* # pages / 2 */
        psize = mmu_psize_defs[mmu_virtual_psize].shift;
        pteg_count = max(rnd_mem_size >> (psize + 1), 1UL << 11);

        return pteg_count << 7;
}

#ifdef CONFIG_MEMORY_HOTPLUG
int create_section_mapping(unsigned long start, unsigned long end)
{
        return htab_bolt_mapping(start, end, __pa(start),
                                 pgprot_val(PAGE_KERNEL), mmu_linear_psize,
                                 mmu_kernel_ssize);
}

int remove_section_mapping(unsigned long start, unsigned long end)
{
        return htab_remove_mapping(start, end, mmu_linear_psize,
                        mmu_kernel_ssize);
}
#endif /* CONFIG_MEMORY_HOTPLUG */

#define FUNCTION_TEXT(A)        ((*(unsigned long *)(A)))

static void __init htab_finish_init(void)
{
        extern unsigned int *htab_call_hpte_insert1;
        extern unsigned int *htab_call_hpte_insert2;
        extern unsigned int *htab_call_hpte_remove;
        extern unsigned int *htab_call_hpte_updatepp;

#ifdef CONFIG_PPC_HAS_HASH_64K
        extern unsigned int *ht64_call_hpte_insert1;
        extern unsigned int *ht64_call_hpte_insert2;
        extern unsigned int *ht64_call_hpte_remove;
        extern unsigned int *ht64_call_hpte_updatepp;

        patch_branch(ht64_call_hpte_insert1,
                FUNCTION_TEXT(ppc_md.hpte_insert),
                BRANCH_SET_LINK);
        patch_branch(ht64_call_hpte_insert2,
                FUNCTION_TEXT(ppc_md.hpte_insert),
                BRANCH_SET_LINK);
        patch_branch(ht64_call_hpte_remove,
                FUNCTION_TEXT(ppc_md.hpte_remove),
                BRANCH_SET_LINK);
        patch_branch(ht64_call_hpte_updatepp,
                FUNCTION_TEXT(ppc_md.hpte_updatepp),
                BRANCH_SET_LINK);

#endif /* CONFIG_PPC_HAS_HASH_64K */

        patch_branch(htab_call_hpte_insert1,
                FUNCTION_TEXT(ppc_md.hpte_insert),
                BRANCH_SET_LINK);
        patch_branch(htab_call_hpte_insert2,
                FUNCTION_TEXT(ppc_md.hpte_insert),
                BRANCH_SET_LINK);
        patch_branch(htab_call_hpte_remove,
                FUNCTION_TEXT(ppc_md.hpte_remove),
                BRANCH_SET_LINK);
        patch_branch(htab_call_hpte_updatepp,
                FUNCTION_TEXT(ppc_md.hpte_updatepp),
                BRANCH_SET_LINK);
}

static void __init htab_initialize(void)
{
        unsigned long table;
        unsigned long pteg_count;
        unsigned long prot;
        unsigned long base = 0, size = 0, limit;
        struct memblock_region *reg;

        DBG(" -> htab_initialize()\n");

        /* Initialize segment sizes */
        htab_init_seg_sizes();

        /* Initialize page sizes */
        htab_init_page_sizes();

        if (mmu_has_feature(MMU_FTR_1T_SEGMENT)) {
                mmu_kernel_ssize = MMU_SEGSIZE_1T;
                mmu_highuser_ssize = MMU_SEGSIZE_1T;
                printk(KERN_INFO "Using 1TB segments\n");
        }

        /*
         * Calculate the required size of the htab.  We want the number of
         * PTEGs to equal one half the number of real pages.
         */ 
        htab_size_bytes = htab_get_table_size();
        pteg_count = htab_size_bytes >> 7;

        htab_hash_mask = pteg_count - 1;

        if (firmware_has_feature(FW_FEATURE_LPAR)) {
                /* Using a hypervisor which owns the htab */
                htab_address = NULL;
                _SDR1 = 0; 
#ifdef CONFIG_FA_DUMP
                /*
                 * If firmware assisted dump is active firmware preserves
                 * the contents of htab along with entire partition memory.
                 * Clear the htab if firmware assisted dump is active so
                 * that we dont end up using old mappings.
                 */
                if (is_fadump_active() && ppc_md.hpte_clear_all)
                        ppc_md.hpte_clear_all();
#endif
        } else {
                /* Find storage for the HPT.  Must be contiguous in
                 * the absolute address space. On cell we want it to be
                 * in the first 2 Gig so we can use it for IOMMU hacks.
                 */
                if (machine_is(cell))
                        limit = 0x80000000;
                else
                        limit = MEMBLOCK_ALLOC_ANYWHERE;

                table = memblock_alloc_base(htab_size_bytes, htab_size_bytes, limit);

                DBG("Hash table allocated at %lx, size: %lx\n", table,
                    htab_size_bytes);

                htab_address = __va(table);

                /* htab absolute addr + encoded htabsize */
                _SDR1 = table + __ilog2(pteg_count) - 11;

                /* Initialize the HPT with no entries */
                memset((void *)table, 0, htab_size_bytes);

                /* Set SDR1 */
                mtspr(SPRN_SDR1, _SDR1);
        }

        prot = pgprot_val(PAGE_KERNEL);

#ifdef CONFIG_DEBUG_PAGEALLOC
        linear_map_hash_count = memblock_end_of_DRAM() >> PAGE_SHIFT;
        linear_map_hash_slots = __va(memblock_alloc_base(linear_map_hash_count,
                                                    1, ppc64_rma_size));
        memset(linear_map_hash_slots, 0, linear_map_hash_count);
#endif /* CONFIG_DEBUG_PAGEALLOC */

        /* On U3 based machines, we need to reserve the DART area and
         * _NOT_ map it to avoid cache paradoxes as it's remapped non
         * cacheable later on
         */

        /* create bolted the linear mapping in the hash table */
        for_each_memblock(memory, reg) {
                base = (unsigned long)__va(reg->base);
                size = reg->size;

                DBG("creating mapping for region: %lx..%lx (prot: %lx)\n",
                    base, size, prot);

#ifdef CONFIG_U3_DART
                /* Do not map the DART space. Fortunately, it will be aligned
                 * in such a way that it will not cross two memblock regions and
                 * will fit within a single 16Mb page.
                 * The DART space is assumed to be a full 16Mb region even if
                 * we only use 2Mb of that space. We will use more of it later
                 * for AGP GART. We have to use a full 16Mb large page.
                 */
                DBG("DART base: %lx\n", dart_tablebase);

                if (dart_tablebase != 0 && dart_tablebase >= base
                    && dart_tablebase < (base + size)) {
                        unsigned long dart_table_end = dart_tablebase + 16 * MB;
                        if (base != dart_tablebase)
                                BUG_ON(htab_bolt_mapping(base, dart_tablebase,
                                                        __pa(base), prot,
                                                        mmu_linear_psize,
                                                        mmu_kernel_ssize));
                        if ((base + size) > dart_table_end)
                                BUG_ON(htab_bolt_mapping(dart_tablebase+16*MB,
                                                        base + size,
                                                        __pa(dart_table_end),
                                                         prot,
                                                         mmu_linear_psize,
                                                         mmu_kernel_ssize));
                        continue;
                }
#endif /* CONFIG_U3_DART */
                BUG_ON(htab_bolt_mapping(base, base + size, __pa(base),
                                prot, mmu_linear_psize, mmu_kernel_ssize));
        }
        memblock_set_current_limit(MEMBLOCK_ALLOC_ANYWHERE);

        /*
         * If we have a memory_limit and we've allocated TCEs then we need to
         * explicitly map the TCE area at the top of RAM. We also cope with the
         * case that the TCEs start below memory_limit.
         * tce_alloc_start/end are 16MB aligned so the mapping should work
         * for either 4K or 16MB pages.
         */
        if (tce_alloc_start) {
                tce_alloc_start = (unsigned long)__va(tce_alloc_start);
                tce_alloc_end = (unsigned long)__va(tce_alloc_end);

                if (base + size >= tce_alloc_start)
                        tce_alloc_start = base + size + 1;

                BUG_ON(htab_bolt_mapping(tce_alloc_start, tce_alloc_end,
                                         __pa(tce_alloc_start), prot,
                                         mmu_linear_psize, mmu_kernel_ssize));
        }

        htab_finish_init();

        DBG(" <- htab_initialize()\n");
}
#undef KB
#undef MB

void __init early_init_mmu(void)
{
        /* Setup initial STAB address in the PACA */
        get_paca()->stab_real = __pa((u64)&initial_stab);
        get_paca()->stab_addr = (u64)&initial_stab;

        /* Initialize the MMU Hash table and create the linear mapping
         * of memory. Has to be done before stab/slb initialization as
         * this is currently where the page size encoding is obtained
         */
        htab_initialize();

        /* Initialize stab / SLB management */
        if (mmu_has_feature(MMU_FTR_SLB))
                slb_initialize();
        else
                stab_initialize(get_paca()->stab_real);
}

#ifdef CONFIG_SMP
void __cpuinit early_init_mmu_secondary(void)
{
        /* Initialize hash table for that CPU */
        if (!firmware_has_feature(FW_FEATURE_LPAR))
                mtspr(SPRN_SDR1, _SDR1);

        /* Initialize STAB/SLB. We use a virtual address as it works
         * in real mode on pSeries.
         */
        if (mmu_has_feature(MMU_FTR_SLB))
                slb_initialize();
        else
                stab_initialize(get_paca()->stab_addr);
}
#endif /* CONFIG_SMP */

/*
 * Called by asm hashtable.S for doing lazy icache flush
 */
unsigned int hash_page_do_lazy_icache(unsigned int pp, pte_t pte, int trap)
{
        struct page *page;

        if (!pfn_valid(pte_pfn(pte)))
                return pp;

        page = pte_page(pte);

        /* page is dirty */
        if (!test_bit(PG_arch_1, &page->flags) && !PageReserved(page)) {
                if (trap == 0x400) {
                        flush_dcache_icache_page(page);
                        set_bit(PG_arch_1, &page->flags);
                } else
                        pp |= HPTE_R_N;
        }
        return pp;
}

#ifdef CONFIG_PPC_MM_SLICES
unsigned int get_paca_psize(unsigned long addr)
{
        u64 lpsizes;
        unsigned char *hpsizes;
        unsigned long index, mask_index;

        if (addr < SLICE_LOW_TOP) {
                lpsizes = get_paca()->context.low_slices_psize;
                index = GET_LOW_SLICE_INDEX(addr);
                return (lpsizes >> (index * 4)) & 0xF;
        }
        hpsizes = get_paca()->context.high_slices_psize;
        index = GET_HIGH_SLICE_INDEX(addr);
        mask_index = index & 0x1;
        return (hpsizes[index >> 1] >> (mask_index * 4)) & 0xF;
}

#else
unsigned int get_paca_psize(unsigned long addr)
{
        return get_paca()->context.user_psize;
}
#endif

/*
 * Demote a segment to using 4k pages.
 * For now this makes the whole process use 4k pages.
 */
#ifdef CONFIG_PPC_64K_PAGES
void demote_segment_4k(struct mm_struct *mm, unsigned long addr)
{
        if (get_slice_psize(mm, addr) == MMU_PAGE_4K)
                return;
        slice_set_range_psize(mm, addr, 1, MMU_PAGE_4K);
#ifdef CONFIG_SPU_BASE
        spu_flush_all_slbs(mm);
#endif
        if (get_paca_psize(addr) != MMU_PAGE_4K) {
                get_paca()->context = mm->context;
                slb_flush_and_rebolt();
        }
}
#endif /* CONFIG_PPC_64K_PAGES */

#ifdef CONFIG_PPC_SUBPAGE_PROT
/*
 * This looks up a 2-bit protection code for a 4k subpage of a 64k page.
 * Userspace sets the subpage permissions using the subpage_prot system call.
 *
 * Result is 0: full permissions, _PAGE_RW: read-only,
 * _PAGE_USER or _PAGE_USER|_PAGE_RW: no access.
 */
static int subpage_protection(struct mm_struct *mm, unsigned long ea)
{
        struct subpage_prot_table *spt = &mm->context.spt;
        u32 spp = 0;
        u32 **sbpm, *sbpp;

        if (ea >= spt->maxaddr)
                return 0;
        if (ea < 0x100000000) {
                /* addresses below 4GB use spt->low_prot */
                sbpm = spt->low_prot;
        } else {
                sbpm = spt->protptrs[ea >> SBP_L3_SHIFT];
                if (!sbpm)
                        return 0;
        }
        sbpp = sbpm[(ea >> SBP_L2_SHIFT) & (SBP_L2_COUNT - 1)];
        if (!sbpp)
                return 0;
        spp = sbpp[(ea >> PAGE_SHIFT) & (SBP_L1_COUNT - 1)];

        /* extract 2-bit bitfield for this 4k subpage */
        spp >>= 30 - 2 * ((ea >> 12) & 0xf);

        /* turn 0,1,2,3 into combination of _PAGE_USER and _PAGE_RW */
        spp = ((spp & 2) ? _PAGE_USER : 0) | ((spp & 1) ? _PAGE_RW : 0);
        return spp;
}

#else /* CONFIG_PPC_SUBPAGE_PROT */
static inline int subpage_protection(struct mm_struct *mm, unsigned long ea)
{
        return 0;
}
#endif

void hash_failure_debug(unsigned long ea, unsigned long access,
                        unsigned long vsid, unsigned long trap,
                        int ssize, int psize, int lpsize, unsigned long pte)
{
        if (!printk_ratelimit())
                return;
        pr_info("mm: Hashing failure ! EA=0x%lx access=0x%lx current=%s\n",
                ea, access, current->comm);
        pr_info("    trap=0x%lx vsid=0x%lx ssize=%d base psize=%d psize %d pte=0x%lx\n",
                trap, vsid, ssize, psize, lpsize, pte);
}

/* Result code is:
 *  0 - handled
 *  1 - normal page fault
 * -1 - critical hash insertion error
 * -2 - access not permitted by subpage protection mechanism
 */
int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
{
        pgd_t *pgdir;
        unsigned long vsid;
        struct mm_struct *mm;
        pte_t *ptep;
        unsigned hugeshift;
        const struct cpumask *tmp;
        int rc, user_region = 0, local = 0;
        int psize, ssize;

        DBG_LOW("hash_page(ea=%016lx, access=%lx, trap=%lx\n",
                ea, access, trap);

        /* Get region & vsid */
        switch (REGION_ID(ea)) {
        case USER_REGION_ID:
                user_region = 1;
                mm = current->mm;
                if (! mm) {
                        DBG_LOW(" user region with no mm !\n");
                        return 1;
                }
                psize = get_slice_psize(mm, ea);
                ssize = user_segment_size(ea);
                vsid = get_vsid(mm->context.id, ea, ssize);
                break;
        case VMALLOC_REGION_ID:
                mm = &init_mm;
                vsid = get_kernel_vsid(ea, mmu_kernel_ssize);
                if (ea < VMALLOC_END)
                        psize = mmu_vmalloc_psize;
                else
                        psize = mmu_io_psize;
                ssize = mmu_kernel_ssize;
                break;
        default:
                /* Not a valid range
                 * Send the problem up to do_page_fault 
                 */
                return 1;
        }
        DBG_LOW(" mm=%p, mm->pgdir=%p, vsid=%016lx\n", mm, mm->pgd, vsid);

        /* Bad address. */
        if (!vsid) {
                DBG_LOW("Bad address!\n");
                return 1;
        }
        /* Get pgdir */
        pgdir = mm->pgd;
        if (pgdir == NULL)
                return 1;

        /* Check CPU locality */
        tmp = cpumask_of(smp_processor_id());
        if (user_region && cpumask_equal(mm_cpumask(mm), tmp))
                local = 1;

#ifndef CONFIG_PPC_64K_PAGES
        /* If we use 4K pages and our psize is not 4K, then we might
         * be hitting a special driver mapping, and need to align the
         * address before we fetch the PTE.
         *
         * It could also be a hugepage mapping, in which case this is
         * not necessary, but it's not harmful, either.
         */
        if (psize != MMU_PAGE_4K)
                ea &= ~((1ul << mmu_psize_defs[psize].shift) - 1);
#endif /* CONFIG_PPC_64K_PAGES */

        /* Get PTE and page size from page tables */
        ptep = find_linux_pte_or_hugepte(pgdir, ea, &hugeshift);
        if (ptep == NULL || !pte_present(*ptep)) {
                DBG_LOW(" no PTE !\n");
                return 1;
        }

        /* Add _PAGE_PRESENT to the required access perm */
        access |= _PAGE_PRESENT;

        /* Pre-check access permissions (will be re-checked atomically
         * in __hash_page_XX but this pre-check is a fast path
         */
        if (access & ~pte_val(*ptep)) {
                DBG_LOW(" no access !\n");
                return 1;
        }

#ifdef CONFIG_HUGETLB_PAGE
        if (hugeshift)
                return __hash_page_huge(ea, access, vsid, ptep, trap, local,
                                        ssize, hugeshift, psize);
#endif /* CONFIG_HUGETLB_PAGE */

#ifndef CONFIG_PPC_64K_PAGES
        DBG_LOW(" i-pte: %016lx\n", pte_val(*ptep));
#else
        DBG_LOW(" i-pte: %016lx %016lx\n", pte_val(*ptep),
                pte_val(*(ptep + PTRS_PER_PTE)));
#endif
        /* Do actual hashing */
#ifdef CONFIG_PPC_64K_PAGES
        /* If _PAGE_4K_PFN is set, make sure this is a 4k segment */
        if ((pte_val(*ptep) & _PAGE_4K_PFN) && psize == MMU_PAGE_64K) {
                demote_segment_4k(mm, ea);
                psize = MMU_PAGE_4K;
        }

        /* If this PTE is non-cacheable and we have restrictions on
         * using non cacheable large pages, then we switch to 4k
         */
        if (mmu_ci_restrictions && psize == MMU_PAGE_64K &&
            (pte_val(*ptep) & _PAGE_NO_CACHE)) {
                if (user_region) {
                        demote_segment_4k(mm, ea);
                        psize = MMU_PAGE_4K;
                } else if (ea < VMALLOC_END) {
                        /*
                         * some driver did a non-cacheable mapping
                         * in vmalloc space, so switch vmalloc
                         * to 4k pages
                         */
                        printk(KERN_ALERT "Reducing vmalloc segment "
                               "to 4kB pages because of "
                               "non-cacheable mapping\n");
                        psize = mmu_vmalloc_psize = MMU_PAGE_4K;
#ifdef CONFIG_SPU_BASE
                        spu_flush_all_slbs(mm);
#endif
                }
        }
        if (user_region) {
                if (psize != get_paca_psize(ea)) {
                        get_paca()->context = mm->context;
                        slb_flush_and_rebolt();
                }
        } else if (get_paca()->vmalloc_sllp !=
                   mmu_psize_defs[mmu_vmalloc_psize].sllp) {
                get_paca()->vmalloc_sllp =
                        mmu_psize_defs[mmu_vmalloc_psize].sllp;
                slb_vmalloc_update();
        }
#endif /* CONFIG_PPC_64K_PAGES */

#ifdef CONFIG_PPC_HAS_HASH_64K
        if (psize == MMU_PAGE_64K)
                rc = __hash_page_64K(ea, access, vsid, ptep, trap, local, ssize);
        else
#endif /* CONFIG_PPC_HAS_HASH_64K */
        {
                int spp = subpage_protection(mm, ea);
                if (access & spp)
                        rc = -2;
                else
                        rc = __hash_page_4K(ea, access, vsid, ptep, trap,
                                            local, ssize, spp);
        }

        /* Dump some info in case of hash insertion failure, they should
         * never happen so it is really useful to know if/when they do
         */
        if (rc == -1)
                hash_failure_debug(ea, access, vsid, trap, ssize, psize,
                                   psize, pte_val(*ptep));
#ifndef CONFIG_PPC_64K_PAGES
        DBG_LOW(" o-pte: %016lx\n", pte_val(*ptep));
#else
        DBG_LOW(" o-pte: %016lx %016lx\n", pte_val(*ptep),
                pte_val(*(ptep + PTRS_PER_PTE)));
#endif
        DBG_LOW(" -> rc=%d\n", rc);
        return rc;
}
EXPORT_SYMBOL_GPL(hash_page);

void hash_preload(struct mm_struct *mm, unsigned long ea,
                  unsigned long access, unsigned long trap)
{
        unsigned long vsid;
        pgd_t *pgdir;
        pte_t *ptep;
        unsigned long flags;
        int rc, ssize, local = 0;

        BUG_ON(REGION_ID(ea) != USER_REGION_ID);

#ifdef CONFIG_PPC_MM_SLICES
        /* We only prefault standard pages for now */
        if (unlikely(get_slice_psize(mm, ea) != mm->context.user_psize))
                return;
#endif

        DBG_LOW("hash_preload(mm=%p, mm->pgdir=%p, ea=%016lx, access=%lx,"
                " trap=%lx\n", mm, mm->pgd, ea, access, trap);

        /* Get Linux PTE if available */
        pgdir = mm->pgd;
        if (pgdir == NULL)
                return;
        ptep = find_linux_pte(pgdir, ea);
        if (!ptep)
                return;

#ifdef CONFIG_PPC_64K_PAGES
        /* If either _PAGE_4K_PFN or _PAGE_NO_CACHE is set (and we are on
         * a 64K kernel), then we don't preload, hash_page() will take
         * care of it once we actually try to access the page.
         * That way we don't have to duplicate all of the logic for segment
         * page size demotion here
         */
        if (pte_val(*ptep) & (_PAGE_4K_PFN | _PAGE_NO_CACHE))
                return;
#endif /* CONFIG_PPC_64K_PAGES */

        /* Get VSID */
        ssize = user_segment_size(ea);
        vsid = get_vsid(mm->context.id, ea, ssize);
        if (!vsid)
                return;

        /* Hash doesn't like irqs */
        local_irq_save(flags);

        /* Is that local to this CPU ? */
        if (cpumask_equal(mm_cpumask(mm), cpumask_of(smp_processor_id())))
                local = 1;

        /* Hash it in */
#ifdef CONFIG_PPC_HAS_HASH_64K
        if (mm->context.user_psize == MMU_PAGE_64K)
                rc = __hash_page_64K(ea, access, vsid, ptep, trap, local, ssize);
        else
#endif /* CONFIG_PPC_HAS_HASH_64K */
                rc = __hash_page_4K(ea, access, vsid, ptep, trap, local, ssize,
                                    subpage_protection(mm, ea));

        /* Dump some info in case of hash insertion failure, they should
         * never happen so it is really useful to know if/when they do
         */
        if (rc == -1)
                hash_failure_debug(ea, access, vsid, trap, ssize,
                                   mm->context.user_psize,
                                   mm->context.user_psize,
                                   pte_val(*ptep));

        local_irq_restore(flags);
}

/* WARNING: This is called from hash_low_64.S, if you change this prototype,
 *          do not forget to update the assembly call site !
 */
void flush_hash_page(unsigned long vpn, real_pte_t pte, int psize, int ssize,
                     int local)
{
        unsigned long hash, index, shift, hidx, slot;

        DBG_LOW("flush_hash_page(vpn=%016lx)\n", vpn);
        pte_iterate_hashed_subpages(pte, psize, vpn, index, shift) {
                hash = hpt_hash(vpn, shift, ssize);
                hidx = __rpte_to_hidx(pte, index);
                if (hidx & _PTEIDX_SECONDARY)
                        hash = ~hash;
                slot = (hash & htab_hash_mask) * HPTES_PER_GROUP;
                slot += hidx & _PTEIDX_GROUP_IX;
                DBG_LOW(" sub %ld: hash=%lx, hidx=%lx\n", index, slot, hidx);
                ppc_md.hpte_invalidate(slot, vpn, psize, ssize, local);
        } pte_iterate_hashed_end();

#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
        /* Transactions are not aborted by tlbiel, only tlbie.
         * Without, syncing a page back to a block device w/ PIO could pick up
         * transactional data (bad!) so we force an abort here.  Before the
         * sync the page will be made read-only, which will flush_hash_page.
         * BIG ISSUE here: if the kernel uses a page from userspace without
         * unmapping it first, it may see the speculated version.
         */
        if (local && cpu_has_feature(CPU_FTR_TM) &&
            current->thread.regs &&
            MSR_TM_ACTIVE(current->thread.regs->msr)) {
                tm_enable();
                tm_abort(TM_CAUSE_TLBI);
        }
#endif
}

void flush_hash_range(unsigned long number, int local)
{
        if (ppc_md.flush_hash_range)
                ppc_md.flush_hash_range(number, local);
        else {
                int i;
                struct ppc64_tlb_batch *batch =
                        &__get_cpu_var(ppc64_tlb_batch);

                for (i = 0; i < number; i++)
                        flush_hash_page(batch->vpn[i], batch->pte[i],
                                        batch->psize, batch->ssize, local);
        }
}

/*
 * low_hash_fault is called when we the low level hash code failed
 * to instert a PTE due to an hypervisor error
 */
void low_hash_fault(struct pt_regs *regs, unsigned long address, int rc)
{
        if (user_mode(regs)) {
#ifdef CONFIG_PPC_SUBPAGE_PROT
                if (rc == -2)
                        _exception(SIGSEGV, regs, SEGV_ACCERR, address);
                else
#endif
                        _exception(SIGBUS, regs, BUS_ADRERR, address);
        } else
                bad_page_fault(regs, address, SIGBUS);
}

long hpte_insert_repeating(unsigned long hash, unsigned long vpn,
                           unsigned long pa, unsigned long rflags,
                           unsigned long vflags, int psize, int ssize)
{
        unsigned long hpte_group;
        long slot;

repeat:
        hpte_group = ((hash & htab_hash_mask) *
                       HPTES_PER_GROUP) & ~0x7UL;

        /* Insert into the hash table, primary slot */
        slot = ppc_md.hpte_insert(hpte_group, vpn, pa, rflags, vflags,
                                  psize, psize, ssize);

        /* Primary is full, try the secondary */
        if (unlikely(slot == -1)) {
                hpte_group = ((~hash & htab_hash_mask) *
                              HPTES_PER_GROUP) & ~0x7UL;
                slot = ppc_md.hpte_insert(hpte_group, vpn, pa, rflags,
                                          vflags | HPTE_V_SECONDARY,
                                          psize, psize, ssize);
                if (slot == -1) {
                        if (mftb() & 0x1)
                                hpte_group = ((hash & htab_hash_mask) *
                                              HPTES_PER_GROUP)&~0x7UL;

                        ppc_md.hpte_remove(hpte_group);
                        goto repeat;
                }
        }

        return slot;
}

#ifdef CONFIG_DEBUG_PAGEALLOC
static void kernel_map_linear_page(unsigned long vaddr, unsigned long lmi)
{
        unsigned long hash;
        unsigned long vsid = get_kernel_vsid(vaddr, mmu_kernel_ssize);
        unsigned long vpn = hpt_vpn(vaddr, vsid, mmu_kernel_ssize);
        unsigned long mode = htab_convert_pte_flags(PAGE_KERNEL);
        long ret;

        hash = hpt_hash(vpn, PAGE_SHIFT, mmu_kernel_ssize);

        /* Don't create HPTE entries for bad address */
        if (!vsid)
                return;

        ret = hpte_insert_repeating(hash, vpn, __pa(vaddr), mode,
                                    HPTE_V_BOLTED,
                                    mmu_linear_psize, mmu_kernel_ssize);

        BUG_ON (ret < 0);
        spin_lock(&linear_map_hash_lock);
        BUG_ON(linear_map_hash_slots[lmi] & 0x80);
        linear_map_hash_slots[lmi] = ret | 0x80;
        spin_unlock(&linear_map_hash_lock);
}

static void kernel_unmap_linear_page(unsigned long vaddr, unsigned long lmi)
{
        unsigned long hash, hidx, slot;
        unsigned long vsid = get_kernel_vsid(vaddr, mmu_kernel_ssize);
        unsigned long vpn = hpt_vpn(vaddr, vsid, mmu_kernel_ssize);

        hash = hpt_hash(vpn, PAGE_SHIFT, mmu_kernel_ssize);
        spin_lock(&linear_map_hash_lock);
        BUG_ON(!(linear_map_hash_slots[lmi] & 0x80));
        hidx = linear_map_hash_slots[lmi] & 0x7f;
        linear_map_hash_slots[lmi] = 0;
        spin_unlock(&linear_map_hash_lock);
        if (hidx & _PTEIDX_SECONDARY)
                hash = ~hash;
        slot = (hash & htab_hash_mask) * HPTES_PER_GROUP;
        slot += hidx & _PTEIDX_GROUP_IX;
        ppc_md.hpte_invalidate(slot, vpn, mmu_linear_psize, mmu_kernel_ssize, 0);
}

void kernel_map_pages(struct page *page, int numpages, int enable)
{
        unsigned long flags, vaddr, lmi;
        int i;

        local_irq_save(flags);
        for (i = 0; i < numpages; i++, page++) {
                vaddr = (unsigned long)page_address(page);
                lmi = __pa(vaddr) >> PAGE_SHIFT;
                if (lmi >= linear_map_hash_count)
                        continue;
                if (enable)
                        kernel_map_linear_page(vaddr, lmi);
                else
                        kernel_unmap_linear_page(vaddr, lmi);
        }
        local_irq_restore(flags);
}
#endif /* CONFIG_DEBUG_PAGEALLOC */

void 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);

        /* On LPAR systems, the first entry is our RMA region,
         * non-LPAR 64-bit hash MMU systems don't have a limitation
         * on real mode access, but using the first entry works well
         * enough. We also clamp it to 1G to avoid some funky things
         * such as RTAS bugs etc...
         */
        ppc64_rma_size = min_t(u64, first_memblock_size, 0x40000000);

        /* Finally limit subsequent allocations */
        memblock_set_current_limit(ppc64_rma_size);
}