// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * PowerPC64 SLB support.
 *
 * Copyright (C) 2004 David Gibson <dwg@au.ibm.com>, IBM
 * Based on earlier code written by:
 * Dave Engebretsen and Mike Corrigan {engebret|mikejc}@us.ibm.com
 *    Copyright (c) 2001 Dave Engebretsen
 * Copyright (C) 2002 Anton Blanchard <anton@au.ibm.com>, IBM
 */

#include <asm/asm-prototypes.h>
#include <asm/mmu.h>
#include <asm/mmu_context.h>
#include <asm/paca.h>
#include <asm/ppc-opcode.h>
#include <asm/cputable.h>
#include <asm/cacheflush.h>
#include <asm/smp.h>
#include <linux/compiler.h>
#include <linux/context_tracking.h>
#include <linux/mm_types.h>
#include <linux/pgtable.h>

#include <asm/udbg.h>
#include <asm/code-patching.h>

#include "internal.h"


enum slb_index {
        LINEAR_INDEX    = 0, /* Kernel linear map  (0xc000000000000000) */
        KSTACK_INDEX    = 1, /* Kernel stack map */
};

static long slb_allocate_user(struct mm_struct *mm, unsigned long ea);

#define slb_esid_mask(ssize)    \
        (((ssize) == MMU_SEGSIZE_256M)? ESID_MASK: ESID_MASK_1T)

static inline unsigned long mk_esid_data(unsigned long ea, int ssize,
                                         enum slb_index index)
{
        return (ea & slb_esid_mask(ssize)) | SLB_ESID_V | index;
}

static inline unsigned long __mk_vsid_data(unsigned long vsid, int ssize,
                                         unsigned long flags)
{
        return (vsid << slb_vsid_shift(ssize)) | flags |
                ((unsigned long) ssize << SLB_VSID_SSIZE_SHIFT);
}

static inline unsigned long mk_vsid_data(unsigned long ea, int ssize,
                                         unsigned long flags)
{
        return __mk_vsid_data(get_kernel_vsid(ea, ssize), ssize, flags);
}

bool stress_slb_enabled __initdata;

static int __init parse_stress_slb(char *p)
{
        stress_slb_enabled = true;
        return 0;
}
early_param("stress_slb", parse_stress_slb);

__ro_after_init DEFINE_STATIC_KEY_FALSE(stress_slb_key);

static void assert_slb_presence(bool present, unsigned long ea)
{
#ifdef CONFIG_DEBUG_VM
        unsigned long tmp;

        WARN_ON_ONCE(mfmsr() & MSR_EE);

        if (!cpu_has_feature(CPU_FTR_ARCH_206))
                return;

        /*
         * slbfee. requires bit 24 (PPC bit 39) be clear in RB. Hardware
         * ignores all other bits from 0-27, so just clear them all.
         */
        ea &= ~((1UL << SID_SHIFT) - 1);
        asm volatile(__PPC_SLBFEE_DOT(%0, %1) : "=r"(tmp) : "r"(ea) : "cr0");

        WARN_ON(present == (tmp == 0));
#endif
}

static inline void slb_shadow_update(unsigned long ea, int ssize,
                                     unsigned long flags,
                                     enum slb_index index)
{
        struct slb_shadow *p = get_slb_shadow();

        /*
         * Clear the ESID first so the entry is not valid while we are
         * updating it.  No write barriers are needed here, provided
         * we only update the current CPU's SLB shadow buffer.
         */
        WRITE_ONCE(p->save_area[index].esid, 0);
        WRITE_ONCE(p->save_area[index].vsid, cpu_to_be64(mk_vsid_data(ea, ssize, flags)));
        WRITE_ONCE(p->save_area[index].esid, cpu_to_be64(mk_esid_data(ea, ssize, index)));
}

static inline void slb_shadow_clear(enum slb_index index)
{
        WRITE_ONCE(get_slb_shadow()->save_area[index].esid, cpu_to_be64(index));
}

static inline void create_shadowed_slbe(unsigned long ea, int ssize,
                                        unsigned long flags,
                                        enum slb_index index)
{
        /*
         * Updating the shadow buffer before writing the SLB ensures
         * we don't get a stale entry here if we get preempted by PHYP
         * between these two statements.
         */
        slb_shadow_update(ea, ssize, flags, index);

        assert_slb_presence(false, ea);
        asm volatile("slbmte  %0,%1" :
                     : "r" (mk_vsid_data(ea, ssize, flags)),
                       "r" (mk_esid_data(ea, ssize, index))
                     : "memory" );
}

/*
 * Insert bolted entries into SLB (which may not be empty, so don't clear
 * slb_cache_ptr).
 */
void __slb_restore_bolted_realmode(void)
{
        struct slb_shadow *p = get_slb_shadow();
        enum slb_index index;

         /* No isync needed because realmode. */
        for (index = 0; index < SLB_NUM_BOLTED; index++) {
                asm volatile("slbmte  %0,%1" :
                     : "r" (be64_to_cpu(p->save_area[index].vsid)),
                       "r" (be64_to_cpu(p->save_area[index].esid)));
        }

        assert_slb_presence(true, local_paca->kstack);
}

/*
 * Insert the bolted entries into an empty SLB.
 */
void slb_restore_bolted_realmode(void)
{
        __slb_restore_bolted_realmode();
        get_paca()->slb_cache_ptr = 0;

        get_paca()->slb_kern_bitmap = (1U << SLB_NUM_BOLTED) - 1;
        get_paca()->slb_used_bitmap = get_paca()->slb_kern_bitmap;
}

/*
 * This flushes all SLB entries including 0, so it must be realmode.
 */
void slb_flush_all_realmode(void)
{
        asm volatile("slbmte %0,%0; slbia" : : "r" (0));
}

static __always_inline void __slb_flush_and_restore_bolted(bool preserve_kernel_lookaside)
{
        struct slb_shadow *p = get_slb_shadow();
        unsigned long ksp_esid_data, ksp_vsid_data;
        u32 ih;

        /*
         * SLBIA IH=1 on ISA v2.05 and newer processors may preserve lookaside
         * information created with Class=0 entries, which we use for kernel
         * SLB entries (the SLB entries themselves are still invalidated).
         *
         * Older processors will ignore this optimisation. Over-invalidation
         * is fine because we never rely on lookaside information existing.
         */
        if (preserve_kernel_lookaside)
                ih = 1;
        else
                ih = 0;

        ksp_esid_data = be64_to_cpu(p->save_area[KSTACK_INDEX].esid);
        ksp_vsid_data = be64_to_cpu(p->save_area[KSTACK_INDEX].vsid);

        asm volatile(PPC_SLBIA(%0)"     \n"
                     "slbmte    %1, %2  \n"
                     :: "i" (ih),
                        "r" (ksp_vsid_data),
                        "r" (ksp_esid_data)
                     : "memory");
}

/*
 * This flushes non-bolted entries, it can be run in virtual mode. Must
 * be called with interrupts disabled.
 */
void slb_flush_and_restore_bolted(void)
{
        BUILD_BUG_ON(SLB_NUM_BOLTED != 2);

        WARN_ON(!irqs_disabled());

        /*
         * We can't take a PMU exception in the following code, so hard
         * disable interrupts.
         */
        hard_irq_disable();

        isync();
        __slb_flush_and_restore_bolted(false);
        isync();

        assert_slb_presence(true, get_paca()->kstack);

        get_paca()->slb_cache_ptr = 0;

        get_paca()->slb_kern_bitmap = (1U << SLB_NUM_BOLTED) - 1;
        get_paca()->slb_used_bitmap = get_paca()->slb_kern_bitmap;
}

void slb_save_contents(struct slb_entry *slb_ptr)
{
        int i;
        unsigned long e, v;

        /* Save slb_cache_ptr value. */
        get_paca()->slb_save_cache_ptr = get_paca()->slb_cache_ptr;

        if (!slb_ptr)
                return;

        for (i = 0; i < mmu_slb_size; i++) {
                asm volatile("slbmfee  %0,%1" : "=r" (e) : "r" (i));
                asm volatile("slbmfev  %0,%1" : "=r" (v) : "r" (i));
                slb_ptr->esid = e;
                slb_ptr->vsid = v;
                slb_ptr++;
        }
}

void slb_dump_contents(struct slb_entry *slb_ptr)
{
        int i, n;
        unsigned long e, v;
        unsigned long llp;

        if (!slb_ptr)
                return;

        pr_err("SLB contents of cpu 0x%x\n", smp_processor_id());
        pr_err("Last SLB entry inserted at slot %d\n", get_paca()->stab_rr);

        for (i = 0; i < mmu_slb_size; i++) {
                e = slb_ptr->esid;
                v = slb_ptr->vsid;
                slb_ptr++;

                if (!e && !v)
                        continue;

                pr_err("%02d %016lx %016lx\n", i, e, v);

                if (!(e & SLB_ESID_V)) {
                        pr_err("\n");
                        continue;
                }
                llp = v & SLB_VSID_LLP;
                if (v & SLB_VSID_B_1T) {
                        pr_err("  1T  ESID=%9lx  VSID=%13lx LLP:%3lx\n",
                               GET_ESID_1T(e),
                               (v & ~SLB_VSID_B) >> SLB_VSID_SHIFT_1T, llp);
                } else {
                        pr_err(" 256M ESID=%9lx  VSID=%13lx LLP:%3lx\n",
                               GET_ESID(e),
                               (v & ~SLB_VSID_B) >> SLB_VSID_SHIFT, llp);
                }
        }
        pr_err("----------------------------------\n");

        /* Dump slb cache entires as well. */
        pr_err("SLB cache ptr value = %d\n", get_paca()->slb_save_cache_ptr);
        pr_err("Valid SLB cache entries:\n");
        n = min_t(int, get_paca()->slb_save_cache_ptr, SLB_CACHE_ENTRIES);
        for (i = 0; i < n; i++)
                pr_err("%02d EA[0-35]=%9x\n", i, get_paca()->slb_cache[i]);
        pr_err("Rest of SLB cache entries:\n");
        for (i = n; i < SLB_CACHE_ENTRIES; i++)
                pr_err("%02d EA[0-35]=%9x\n", i, get_paca()->slb_cache[i]);
}

void slb_vmalloc_update(void)
{
        /*
         * vmalloc is not bolted, so just have to flush non-bolted.
         */
        slb_flush_and_restore_bolted();
}

static bool preload_hit(struct thread_info *ti, unsigned long esid)
{
        unsigned char i;

        for (i = 0; i < ti->slb_preload_nr; i++) {
                unsigned char idx;

                idx = (ti->slb_preload_tail + i) % SLB_PRELOAD_NR;
                if (esid == ti->slb_preload_esid[idx])
                        return true;
        }
        return false;
}

static bool preload_add(struct thread_info *ti, unsigned long ea)
{
        unsigned char idx;
        unsigned long esid;

        if (mmu_has_feature(MMU_FTR_1T_SEGMENT)) {
                /* EAs are stored >> 28 so 256MB segments don't need clearing */
                if (ea & ESID_MASK_1T)
                        ea &= ESID_MASK_1T;
        }

        esid = ea >> SID_SHIFT;

        if (preload_hit(ti, esid))
                return false;

        idx = (ti->slb_preload_tail + ti->slb_preload_nr) % SLB_PRELOAD_NR;
        ti->slb_preload_esid[idx] = esid;
        if (ti->slb_preload_nr == SLB_PRELOAD_NR)
                ti->slb_preload_tail = (ti->slb_preload_tail + 1) % SLB_PRELOAD_NR;
        else
                ti->slb_preload_nr++;

        return true;
}

static void preload_age(struct thread_info *ti)
{
        if (!ti->slb_preload_nr)
                return;
        ti->slb_preload_nr--;
        ti->slb_preload_tail = (ti->slb_preload_tail + 1) % SLB_PRELOAD_NR;
}

void slb_setup_new_exec(void)
{
        struct thread_info *ti = current_thread_info();
        struct mm_struct *mm = current->mm;
        unsigned long exec = 0x10000000;

        WARN_ON(irqs_disabled());

        /*
         * preload cache can only be used to determine whether a SLB
         * entry exists if it does not start to overflow.
         */
        if (ti->slb_preload_nr + 2 > SLB_PRELOAD_NR)
                return;

        hard_irq_disable();

        /*
         * We have no good place to clear the slb preload cache on exec,
         * flush_thread is about the earliest arch hook but that happens
         * after we switch to the mm and have aleady preloaded the SLBEs.
         *
         * For the most part that's probably okay to use entries from the
         * previous exec, they will age out if unused. It may turn out to
         * be an advantage to clear the cache before switching to it,
         * however.
         */

        /*
         * preload some userspace segments into the SLB.
         * Almost all 32 and 64bit PowerPC executables are linked at
         * 0x10000000 so it makes sense to preload this segment.
         */
        if (!is_kernel_addr(exec)) {
                if (preload_add(ti, exec))
                        slb_allocate_user(mm, exec);
        }

        /* Libraries and mmaps. */
        if (!is_kernel_addr(mm->mmap_base)) {
                if (preload_add(ti, mm->mmap_base))
                        slb_allocate_user(mm, mm->mmap_base);
        }

        /* see switch_slb */
        asm volatile("isync" : : : "memory");

        local_irq_enable();
}

void preload_new_slb_context(unsigned long start, unsigned long sp)
{
        struct thread_info *ti = current_thread_info();
        struct mm_struct *mm = current->mm;
        unsigned long heap = mm->start_brk;

        WARN_ON(irqs_disabled());

        /* see above */
        if (ti->slb_preload_nr + 3 > SLB_PRELOAD_NR)
                return;

        hard_irq_disable();

        /* Userspace entry address. */
        if (!is_kernel_addr(start)) {
                if (preload_add(ti, start))
                        slb_allocate_user(mm, start);
        }

        /* Top of stack, grows down. */
        if (!is_kernel_addr(sp)) {
                if (preload_add(ti, sp))
                        slb_allocate_user(mm, sp);
        }

        /* Bottom of heap, grows up. */
        if (heap && !is_kernel_addr(heap)) {
                if (preload_add(ti, heap))
                        slb_allocate_user(mm, heap);
        }

        /* see switch_slb */
        asm volatile("isync" : : : "memory");

        local_irq_enable();
}

static void slb_cache_slbie_kernel(unsigned int index)
{
        unsigned long slbie_data = get_paca()->slb_cache[index];
        unsigned long ksp = get_paca()->kstack;

        slbie_data <<= SID_SHIFT;
        slbie_data |= 0xc000000000000000ULL;
        if ((ksp & slb_esid_mask(mmu_kernel_ssize)) == slbie_data)
                return;
        slbie_data |= mmu_kernel_ssize << SLBIE_SSIZE_SHIFT;

        asm volatile("slbie %0" : : "r" (slbie_data));
}

static void slb_cache_slbie_user(unsigned int index)
{
        unsigned long slbie_data = get_paca()->slb_cache[index];

        slbie_data <<= SID_SHIFT;
        slbie_data |= user_segment_size(slbie_data) << SLBIE_SSIZE_SHIFT;
        slbie_data |= SLBIE_C; /* user slbs have C=1 */

        asm volatile("slbie %0" : : "r" (slbie_data));
}

/* Flush all user entries from the segment table of the current processor. */
void switch_slb(struct task_struct *tsk, struct mm_struct *mm)
{
        struct thread_info *ti = task_thread_info(tsk);
        unsigned char i;

        /*
         * We need interrupts hard-disabled here, not just soft-disabled,
         * so that a PMU interrupt can't occur, which might try to access
         * user memory (to get a stack trace) and possible cause an SLB miss
         * which would update the slb_cache/slb_cache_ptr fields in the PACA.
         */
        hard_irq_disable();
        isync();
        if (stress_slb()) {
                __slb_flush_and_restore_bolted(false);
                isync();
                get_paca()->slb_cache_ptr = 0;
                get_paca()->slb_kern_bitmap = (1U << SLB_NUM_BOLTED) - 1;

        } else if (cpu_has_feature(CPU_FTR_ARCH_300)) {
                /*
                 * SLBIA IH=3 invalidates all Class=1 SLBEs and their
                 * associated lookaside structures, which matches what
                 * switch_slb wants. So ARCH_300 does not use the slb
                 * cache.
                 */
                asm volatile(PPC_SLBIA(3));

        } else {
                unsigned long offset = get_paca()->slb_cache_ptr;

                if (!mmu_has_feature(MMU_FTR_NO_SLBIE_B) &&
                    offset <= SLB_CACHE_ENTRIES) {
                        /*
                         * Could assert_slb_presence(true) here, but
                         * hypervisor or machine check could have come
                         * in and removed the entry at this point.
                         */

                        for (i = 0; i < offset; i++)
                                slb_cache_slbie_user(i);

                        /* Workaround POWER5 < DD2.1 issue */
                        if (!cpu_has_feature(CPU_FTR_ARCH_207S) && offset == 1)
                                slb_cache_slbie_user(0);

                } else {
                        /* Flush but retain kernel lookaside information */
                        __slb_flush_and_restore_bolted(true);
                        isync();

                        get_paca()->slb_kern_bitmap = (1U << SLB_NUM_BOLTED) - 1;
                }

                get_paca()->slb_cache_ptr = 0;
        }
        get_paca()->slb_used_bitmap = get_paca()->slb_kern_bitmap;

        copy_mm_to_paca(mm);

        /*
         * We gradually age out SLBs after a number of context switches to
         * reduce reload overhead of unused entries (like we do with FP/VEC
         * reload). Each time we wrap 256 switches, take an entry out of the
         * SLB preload cache.
         */
        tsk->thread.load_slb++;
        if (!tsk->thread.load_slb) {
                unsigned long pc = KSTK_EIP(tsk);

                preload_age(ti);
                preload_add(ti, pc);
        }

        for (i = 0; i < ti->slb_preload_nr; i++) {
                unsigned char idx;
                unsigned long ea;

                idx = (ti->slb_preload_tail + i) % SLB_PRELOAD_NR;
                ea = (unsigned long)ti->slb_preload_esid[idx] << SID_SHIFT;

                slb_allocate_user(mm, ea);
        }

        /*
         * Synchronize slbmte preloads with possible subsequent user memory
         * address accesses by the kernel (user mode won't happen until
         * rfid, which is safe).
         */
        isync();
}

void slb_set_size(u16 size)
{
        mmu_slb_size = size;
}

void slb_initialize(void)
{
        unsigned long linear_llp, vmalloc_llp, io_llp;
        unsigned long lflags;
        static int slb_encoding_inited;
#ifdef CONFIG_SPARSEMEM_VMEMMAP
        unsigned long vmemmap_llp;
#endif

        /* Prepare our SLB miss handler based on our page size */
        linear_llp = mmu_psize_defs[mmu_linear_psize].sllp;
        io_llp = mmu_psize_defs[mmu_io_psize].sllp;
        vmalloc_llp = mmu_psize_defs[mmu_vmalloc_psize].sllp;
        get_paca()->vmalloc_sllp = SLB_VSID_KERNEL | vmalloc_llp;
#ifdef CONFIG_SPARSEMEM_VMEMMAP
        vmemmap_llp = mmu_psize_defs[mmu_vmemmap_psize].sllp;
#endif
        if (!slb_encoding_inited) {
                slb_encoding_inited = 1;
                pr_devel("SLB: linear  LLP = %04lx\n", linear_llp);
                pr_devel("SLB: io      LLP = %04lx\n", io_llp);
#ifdef CONFIG_SPARSEMEM_VMEMMAP
                pr_devel("SLB: vmemmap LLP = %04lx\n", vmemmap_llp);
#endif
        }

        get_paca()->stab_rr = SLB_NUM_BOLTED - 1;
        get_paca()->slb_kern_bitmap = (1U << SLB_NUM_BOLTED) - 1;
        get_paca()->slb_used_bitmap = get_paca()->slb_kern_bitmap;

        lflags = SLB_VSID_KERNEL | linear_llp;

        /* Invalidate the entire SLB (even entry 0) & all the ERATS */
        asm volatile("isync":::"memory");
        asm volatile("slbmte  %0,%0"::"r" (0) : "memory");
        asm volatile("isync; slbia; isync":::"memory");
        create_shadowed_slbe(PAGE_OFFSET, mmu_kernel_ssize, lflags, LINEAR_INDEX);

        /*
         * For the boot cpu, we're running on the stack in init_thread_union,
         * which is in the first segment of the linear mapping, and also
         * get_paca()->kstack hasn't been initialized yet.
         * For secondary cpus, we need to bolt the kernel stack entry now.
         */
        slb_shadow_clear(KSTACK_INDEX);
        if (raw_smp_processor_id() != boot_cpuid &&
            (get_paca()->kstack & slb_esid_mask(mmu_kernel_ssize)) > PAGE_OFFSET)
                create_shadowed_slbe(get_paca()->kstack,
                                     mmu_kernel_ssize, lflags, KSTACK_INDEX);

        asm volatile("isync":::"memory");
}

static void slb_cache_update(unsigned long esid_data)
{
        int slb_cache_index;

        if (cpu_has_feature(CPU_FTR_ARCH_300))
                return; /* ISAv3.0B and later does not use slb_cache */

        if (stress_slb())
                return;

        /*
         * Now update slb cache entries
         */
        slb_cache_index = local_paca->slb_cache_ptr;
        if (slb_cache_index < SLB_CACHE_ENTRIES) {
                /*
                 * We have space in slb cache for optimized switch_slb().
                 * Top 36 bits from esid_data as per ISA
                 */
                local_paca->slb_cache[slb_cache_index++] = esid_data >> SID_SHIFT;
                local_paca->slb_cache_ptr++;
        } else {
                /*
                 * Our cache is full and the current cache content strictly
                 * doesn't indicate the active SLB conents. Bump the ptr
                 * so that switch_slb() will ignore the cache.
                 */
                local_paca->slb_cache_ptr = SLB_CACHE_ENTRIES + 1;
        }
}

static enum slb_index alloc_slb_index(bool kernel)
{
        enum slb_index index;

        /*
         * The allocation bitmaps can become out of synch with the SLB
         * when the _switch code does slbie when bolting a new stack
         * segment and it must not be anywhere else in the SLB. This leaves
         * a kernel allocated entry that is unused in the SLB. With very
         * large systems or small segment sizes, the bitmaps could slowly
         * fill with these entries. They will eventually be cleared out
         * by the round robin allocator in that case, so it's probably not
         * worth accounting for.
         */

        /*
         * SLBs beyond 32 entries are allocated with stab_rr only
         * POWER7/8/9 have 32 SLB entries, this could be expanded if a
         * future CPU has more.
         */
        if (local_paca->slb_used_bitmap != U32_MAX) {
                index = ffz(local_paca->slb_used_bitmap);
                local_paca->slb_used_bitmap |= 1U << index;
                if (kernel)
                        local_paca->slb_kern_bitmap |= 1U << index;
        } else {
                /* round-robin replacement of slb starting at SLB_NUM_BOLTED. */
                index = local_paca->stab_rr;
                if (index < (mmu_slb_size - 1))
                        index++;
                else
                        index = SLB_NUM_BOLTED;
                local_paca->stab_rr = index;
                if (index < 32) {
                        if (kernel)
                                local_paca->slb_kern_bitmap |= 1U << index;
                        else
                                local_paca->slb_kern_bitmap &= ~(1U << index);
                }
        }
        BUG_ON(index < SLB_NUM_BOLTED);

        return index;
}

static long slb_insert_entry(unsigned long ea, unsigned long context,
                                unsigned long flags, int ssize, bool kernel)
{
        unsigned long vsid;
        unsigned long vsid_data, esid_data;
        enum slb_index index;

        vsid = get_vsid(context, ea, ssize);
        if (!vsid)
                return -EFAULT;

        /*
         * There must not be a kernel SLB fault in alloc_slb_index or before
         * slbmte here or the allocation bitmaps could get out of whack with
         * the SLB.
         *
         * User SLB faults or preloads take this path which might get inlined
         * into the caller, so add compiler barriers here to ensure unsafe
         * memory accesses do not come between.
         */
        barrier();

        index = alloc_slb_index(kernel);

        vsid_data = __mk_vsid_data(vsid, ssize, flags);
        esid_data = mk_esid_data(ea, ssize, index);

        /*
         * No need for an isync before or after this slbmte. The exception
         * we enter with and the rfid we exit with are context synchronizing.
         * User preloads should add isync afterwards in case the kernel
         * accesses user memory before it returns to userspace with rfid.
         */
        assert_slb_presence(false, ea);
        if (stress_slb()) {
                int slb_cache_index = local_paca->slb_cache_ptr;

                /*
                 * stress_slb() does not use slb cache, repurpose as a
                 * cache of inserted (non-bolted) kernel SLB entries. All
                 * non-bolted kernel entries are flushed on any user fault,
                 * or if there are already 3 non-boled kernel entries.
                 */
                BUILD_BUG_ON(SLB_CACHE_ENTRIES < 3);
                if (!kernel || slb_cache_index == 3) {
                        int i;

                        for (i = 0; i < slb_cache_index; i++)
                                slb_cache_slbie_kernel(i);
                        slb_cache_index = 0;
                }

                if (kernel)
                        local_paca->slb_cache[slb_cache_index++] = esid_data >> SID_SHIFT;
                local_paca->slb_cache_ptr = slb_cache_index;
        }
        asm volatile("slbmte %0, %1" : : "r" (vsid_data), "r" (esid_data));

        barrier();

        if (!kernel)
                slb_cache_update(esid_data);

        return 0;
}

static long slb_allocate_kernel(unsigned long ea, unsigned long id)
{
        unsigned long context;
        unsigned long flags;
        int ssize;

        if (id == LINEAR_MAP_REGION_ID) {

                /* We only support upto H_MAX_PHYSMEM_BITS */
                if ((ea & EA_MASK) > (1UL << H_MAX_PHYSMEM_BITS))
                        return -EFAULT;

                flags = SLB_VSID_KERNEL | mmu_psize_defs[mmu_linear_psize].sllp;

#ifdef CONFIG_SPARSEMEM_VMEMMAP
        } else if (id == VMEMMAP_REGION_ID) {

                if (ea >= H_VMEMMAP_END)
                        return -EFAULT;

                flags = SLB_VSID_KERNEL | mmu_psize_defs[mmu_vmemmap_psize].sllp;
#endif
        } else if (id == VMALLOC_REGION_ID) {

                if (ea >= H_VMALLOC_END)
                        return -EFAULT;

                flags = local_paca->vmalloc_sllp;

        } else if (id == IO_REGION_ID) {

                if (ea >= H_KERN_IO_END)
                        return -EFAULT;

                flags = SLB_VSID_KERNEL | mmu_psize_defs[mmu_io_psize].sllp;

        } else {
                return -EFAULT;
        }

        ssize = MMU_SEGSIZE_1T;
        if (!mmu_has_feature(MMU_FTR_1T_SEGMENT))
                ssize = MMU_SEGSIZE_256M;

        context = get_kernel_context(ea);

        return slb_insert_entry(ea, context, flags, ssize, true);
}

static long slb_allocate_user(struct mm_struct *mm, unsigned long ea)
{
        unsigned long context;
        unsigned long flags;
        int bpsize;
        int ssize;

        /*
         * consider this as bad access if we take a SLB miss
         * on an address above addr limit.
         */
        if (ea >= mm_ctx_slb_addr_limit(&mm->context))
                return -EFAULT;

        context = get_user_context(&mm->context, ea);
        if (!context)
                return -EFAULT;

        if (unlikely(ea >= H_PGTABLE_RANGE)) {
                WARN_ON(1);
                return -EFAULT;
        }

        ssize = user_segment_size(ea);

        bpsize = get_slice_psize(mm, ea);
        flags = SLB_VSID_USER | mmu_psize_defs[bpsize].sllp;

        return slb_insert_entry(ea, context, flags, ssize, false);
}

long do_slb_fault(struct pt_regs *regs, unsigned long ea)
{
        unsigned long id = get_region_id(ea);

        /* IRQs are not reconciled here, so can't check irqs_disabled */
        VM_WARN_ON(mfmsr() & MSR_EE);

        if (unlikely(!(regs->msr & MSR_RI)))
                return -EINVAL;

        /*
         * SLB kernel faults must be very careful not to touch anything
         * that is not bolted. E.g., PACA and global variables are okay,
         * mm->context stuff is not.
         *
         * SLB user faults can access all of kernel memory, but must be
         * careful not to touch things like IRQ state because it is not
         * "reconciled" here. The difficulty is that we must use
         * fast_exception_return to return from kernel SLB faults without
         * looking at possible non-bolted memory. We could test user vs
         * kernel faults in the interrupt handler asm and do a full fault,
         * reconcile, ret_from_except for user faults which would make them
         * first class kernel code. But for performance it's probably nicer
         * if they go via fast_exception_return too.
         */
        if (id >= LINEAR_MAP_REGION_ID) {
                long err;
#ifdef CONFIG_DEBUG_VM
                /* Catch recursive kernel SLB faults. */
                BUG_ON(local_paca->in_kernel_slb_handler);
                local_paca->in_kernel_slb_handler = 1;
#endif
                err = slb_allocate_kernel(ea, id);
#ifdef CONFIG_DEBUG_VM
                local_paca->in_kernel_slb_handler = 0;
#endif
                return err;
        } else {
                struct mm_struct *mm = current->mm;
                long err;

                if (unlikely(!mm))
                        return -EFAULT;

                err = slb_allocate_user(mm, ea);
                if (!err)
                        preload_add(current_thread_info(), ea);

                return err;
        }
}

void do_bad_slb_fault(struct pt_regs *regs, unsigned long ea, long err)
{
        if (err == -EFAULT) {
                if (user_mode(regs))
                        _exception(SIGSEGV, regs, SEGV_BNDERR, ea);
                else
                        bad_page_fault(regs, ea, SIGSEGV);
        } else if (err == -EINVAL) {
                unrecoverable_exception(regs);
        } else {
                BUG();
        }
}