Merge tag 'trace-3.8-rc3-regression-fix' of git://git.kernel.org/pub/scm/linux/kernel...

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / arch / powerpc / kvm / book3s_hv_rm_mmu.c

/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License, version 2, as
 * published by the Free Software Foundation.
 *
 * Copyright 2010-2011 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
 */

#include <linux/types.h>
#include <linux/string.h>
#include <linux/kvm.h>
#include <linux/kvm_host.h>
#include <linux/hugetlb.h>
#include <linux/module.h>

#include <asm/tlbflush.h>
#include <asm/kvm_ppc.h>
#include <asm/kvm_book3s.h>
#include <asm/mmu-hash64.h>
#include <asm/hvcall.h>
#include <asm/synch.h>
#include <asm/ppc-opcode.h>

/* Translate address of a vmalloc'd thing to a linear map address */
static void *real_vmalloc_addr(void *x)
{
        unsigned long addr = (unsigned long) x;
        pte_t *p;

        p = find_linux_pte(swapper_pg_dir, addr);
        if (!p || !pte_present(*p))
                return NULL;
        /* assume we don't have huge pages in vmalloc space... */
        addr = (pte_pfn(*p) << PAGE_SHIFT) | (addr & ~PAGE_MASK);
        return __va(addr);
}

/* Return 1 if we need to do a global tlbie, 0 if we can use tlbiel */
static int global_invalidates(struct kvm *kvm, unsigned long flags)
{
        int global;

        /*
         * If there is only one vcore, and it's currently running,
         * we can use tlbiel as long as we mark all other physical
         * cores as potentially having stale TLB entries for this lpid.
         * If we're not using MMU notifiers, we never take pages away
         * from the guest, so we can use tlbiel if requested.
         * Otherwise, don't use tlbiel.
         */
        if (kvm->arch.online_vcores == 1 && local_paca->kvm_hstate.kvm_vcore)
                global = 0;
        else if (kvm->arch.using_mmu_notifiers)
                global = 1;
        else
                global = !(flags & H_LOCAL);

        if (!global) {
                /* any other core might now have stale TLB entries... */
                smp_wmb();
                cpumask_setall(&kvm->arch.need_tlb_flush);
                cpumask_clear_cpu(local_paca->kvm_hstate.kvm_vcore->pcpu,
                                  &kvm->arch.need_tlb_flush);
        }

        return global;
}

/*
 * Add this HPTE into the chain for the real page.
 * Must be called with the chain locked; it unlocks the chain.
 */
void kvmppc_add_revmap_chain(struct kvm *kvm, struct revmap_entry *rev,
                             unsigned long *rmap, long pte_index, int realmode)
{
        struct revmap_entry *head, *tail;
        unsigned long i;

        if (*rmap & KVMPPC_RMAP_PRESENT) {
                i = *rmap & KVMPPC_RMAP_INDEX;
                head = &kvm->arch.revmap[i];
                if (realmode)
                        head = real_vmalloc_addr(head);
                tail = &kvm->arch.revmap[head->back];
                if (realmode)
                        tail = real_vmalloc_addr(tail);
                rev->forw = i;
                rev->back = head->back;
                tail->forw = pte_index;
                head->back = pte_index;
        } else {
                rev->forw = rev->back = pte_index;
                *rmap = (*rmap & ~KVMPPC_RMAP_INDEX) |
                        pte_index | KVMPPC_RMAP_PRESENT;
        }
        unlock_rmap(rmap);
}
EXPORT_SYMBOL_GPL(kvmppc_add_revmap_chain);

/*
 * Note modification of an HPTE; set the HPTE modified bit
 * if anyone is interested.
 */
static inline void note_hpte_modification(struct kvm *kvm,
                                          struct revmap_entry *rev)
{
        if (atomic_read(&kvm->arch.hpte_mod_interest))
                rev->guest_rpte |= HPTE_GR_MODIFIED;
}

/* Remove this HPTE from the chain for a real page */
static void remove_revmap_chain(struct kvm *kvm, long pte_index,
                                struct revmap_entry *rev,
                                unsigned long hpte_v, unsigned long hpte_r)
{
        struct revmap_entry *next, *prev;
        unsigned long gfn, ptel, head;
        struct kvm_memory_slot *memslot;
        unsigned long *rmap;
        unsigned long rcbits;

        rcbits = hpte_r & (HPTE_R_R | HPTE_R_C);
        ptel = rev->guest_rpte |= rcbits;
        gfn = hpte_rpn(ptel, hpte_page_size(hpte_v, ptel));
        memslot = __gfn_to_memslot(kvm_memslots(kvm), gfn);
        if (!memslot)
                return;

        rmap = real_vmalloc_addr(&memslot->arch.rmap[gfn - memslot->base_gfn]);
        lock_rmap(rmap);

        head = *rmap & KVMPPC_RMAP_INDEX;
        next = real_vmalloc_addr(&kvm->arch.revmap[rev->forw]);
        prev = real_vmalloc_addr(&kvm->arch.revmap[rev->back]);
        next->back = rev->back;
        prev->forw = rev->forw;
        if (head == pte_index) {
                head = rev->forw;
                if (head == pte_index)
                        *rmap &= ~(KVMPPC_RMAP_PRESENT | KVMPPC_RMAP_INDEX);
                else
                        *rmap = (*rmap & ~KVMPPC_RMAP_INDEX) | head;
        }
        *rmap |= rcbits << KVMPPC_RMAP_RC_SHIFT;
        unlock_rmap(rmap);
}

static pte_t lookup_linux_pte(pgd_t *pgdir, unsigned long hva,
                              int writing, unsigned long *pte_sizep)
{
        pte_t *ptep;
        unsigned long ps = *pte_sizep;
        unsigned int shift;

        ptep = find_linux_pte_or_hugepte(pgdir, hva, &shift);
        if (!ptep)
                return __pte(0);
        if (shift)
                *pte_sizep = 1ul << shift;
        else
                *pte_sizep = PAGE_SIZE;
        if (ps > *pte_sizep)
                return __pte(0);
        if (!pte_present(*ptep))
                return __pte(0);
        return kvmppc_read_update_linux_pte(ptep, writing);
}

static inline void unlock_hpte(unsigned long *hpte, unsigned long hpte_v)
{
        asm volatile(PPC_RELEASE_BARRIER "" : : : "memory");
        hpte[0] = hpte_v;
}

long kvmppc_do_h_enter(struct kvm *kvm, unsigned long flags,
                       long pte_index, unsigned long pteh, unsigned long ptel,
                       pgd_t *pgdir, bool realmode, unsigned long *pte_idx_ret)
{
        unsigned long i, pa, gpa, gfn, psize;
        unsigned long slot_fn, hva;
        unsigned long *hpte;
        struct revmap_entry *rev;
        unsigned long g_ptel;
        struct kvm_memory_slot *memslot;
        unsigned long *physp, pte_size;
        unsigned long is_io;
        unsigned long *rmap;
        pte_t pte;
        unsigned int writing;
        unsigned long mmu_seq;
        unsigned long rcbits;

        psize = hpte_page_size(pteh, ptel);
        if (!psize)
                return H_PARAMETER;
        writing = hpte_is_writable(ptel);
        pteh &= ~(HPTE_V_HVLOCK | HPTE_V_ABSENT | HPTE_V_VALID);
        ptel &= ~HPTE_GR_RESERVED;
        g_ptel = ptel;

        /* used later to detect if we might have been invalidated */
        mmu_seq = kvm->mmu_notifier_seq;
        smp_rmb();

        /* Find the memslot (if any) for this address */
        gpa = (ptel & HPTE_R_RPN) & ~(psize - 1);
        gfn = gpa >> PAGE_SHIFT;
        memslot = __gfn_to_memslot(kvm_memslots(kvm), gfn);
        pa = 0;
        is_io = ~0ul;
        rmap = NULL;
        if (!(memslot && !(memslot->flags & KVM_MEMSLOT_INVALID))) {
                /* PPC970 can't do emulated MMIO */
                if (!cpu_has_feature(CPU_FTR_ARCH_206))
                        return H_PARAMETER;
                /* Emulated MMIO - mark this with key=31 */
                pteh |= HPTE_V_ABSENT;
                ptel |= HPTE_R_KEY_HI | HPTE_R_KEY_LO;
                goto do_insert;
        }

        /* Check if the requested page fits entirely in the memslot. */
        if (!slot_is_aligned(memslot, psize))
                return H_PARAMETER;
        slot_fn = gfn - memslot->base_gfn;
        rmap = &memslot->arch.rmap[slot_fn];

        if (!kvm->arch.using_mmu_notifiers) {
                physp = memslot->arch.slot_phys;
                if (!physp)
                        return H_PARAMETER;
                physp += slot_fn;
                if (realmode)
                        physp = real_vmalloc_addr(physp);
                pa = *physp;
                if (!pa)
                        return H_TOO_HARD;
                is_io = pa & (HPTE_R_I | HPTE_R_W);
                pte_size = PAGE_SIZE << (pa & KVMPPC_PAGE_ORDER_MASK);
                pa &= PAGE_MASK;
        } else {
                /* Translate to host virtual address */
                hva = __gfn_to_hva_memslot(memslot, gfn);

                /* Look up the Linux PTE for the backing page */
                pte_size = psize;
                pte = lookup_linux_pte(pgdir, hva, writing, &pte_size);
                if (pte_present(pte)) {
                        if (writing && !pte_write(pte))
                                /* make the actual HPTE be read-only */
                                ptel = hpte_make_readonly(ptel);
                        is_io = hpte_cache_bits(pte_val(pte));
                        pa = pte_pfn(pte) << PAGE_SHIFT;
                }
        }

        if (pte_size < psize)
                return H_PARAMETER;
        if (pa && pte_size > psize)
                pa |= gpa & (pte_size - 1);

        ptel &= ~(HPTE_R_PP0 - psize);
        ptel |= pa;

        if (pa)
                pteh |= HPTE_V_VALID;
        else
                pteh |= HPTE_V_ABSENT;

        /* Check WIMG */
        if (is_io != ~0ul && !hpte_cache_flags_ok(ptel, is_io)) {
                if (is_io)
                        return H_PARAMETER;
                /*
                 * Allow guest to map emulated device memory as
                 * uncacheable, but actually make it cacheable.
                 */
                ptel &= ~(HPTE_R_W|HPTE_R_I|HPTE_R_G);
                ptel |= HPTE_R_M;
        }

        /* Find and lock the HPTEG slot to use */
 do_insert:
        if (pte_index >= kvm->arch.hpt_npte)
                return H_PARAMETER;
        if (likely((flags & H_EXACT) == 0)) {
                pte_index &= ~7UL;
                hpte = (unsigned long *)(kvm->arch.hpt_virt + (pte_index << 4));
                for (i = 0; i < 8; ++i) {
                        if ((*hpte & HPTE_V_VALID) == 0 &&
                            try_lock_hpte(hpte, HPTE_V_HVLOCK | HPTE_V_VALID |
                                          HPTE_V_ABSENT))
                                break;
                        hpte += 2;
                }
                if (i == 8) {
                        /*
                         * Since try_lock_hpte doesn't retry (not even stdcx.
                         * failures), it could be that there is a free slot
                         * but we transiently failed to lock it.  Try again,
                         * actually locking each slot and checking it.
                         */
                        hpte -= 16;
                        for (i = 0; i < 8; ++i) {
                                while (!try_lock_hpte(hpte, HPTE_V_HVLOCK))
                                        cpu_relax();
                                if (!(*hpte & (HPTE_V_VALID | HPTE_V_ABSENT)))
                                        break;
                                *hpte &= ~HPTE_V_HVLOCK;
                                hpte += 2;
                        }
                        if (i == 8)
                                return H_PTEG_FULL;
                }
                pte_index += i;
        } else {
                hpte = (unsigned long *)(kvm->arch.hpt_virt + (pte_index << 4));
                if (!try_lock_hpte(hpte, HPTE_V_HVLOCK | HPTE_V_VALID |
                                   HPTE_V_ABSENT)) {
                        /* Lock the slot and check again */
                        while (!try_lock_hpte(hpte, HPTE_V_HVLOCK))
                                cpu_relax();
                        if (*hpte & (HPTE_V_VALID | HPTE_V_ABSENT)) {
                                *hpte &= ~HPTE_V_HVLOCK;
                                return H_PTEG_FULL;
                        }
                }
        }

        /* Save away the guest's idea of the second HPTE dword */
        rev = &kvm->arch.revmap[pte_index];
        if (realmode)
                rev = real_vmalloc_addr(rev);
        if (rev) {
                rev->guest_rpte = g_ptel;
                note_hpte_modification(kvm, rev);
        }

        /* Link HPTE into reverse-map chain */
        if (pteh & HPTE_V_VALID) {
                if (realmode)
                        rmap = real_vmalloc_addr(rmap);
                lock_rmap(rmap);
                /* Check for pending invalidations under the rmap chain lock */
                if (kvm->arch.using_mmu_notifiers &&
                    mmu_notifier_retry(kvm, mmu_seq)) {
                        /* inval in progress, write a non-present HPTE */
                        pteh |= HPTE_V_ABSENT;
                        pteh &= ~HPTE_V_VALID;
                        unlock_rmap(rmap);
                } else {
                        kvmppc_add_revmap_chain(kvm, rev, rmap, pte_index,
                                                realmode);
                        /* Only set R/C in real HPTE if already set in *rmap */
                        rcbits = *rmap >> KVMPPC_RMAP_RC_SHIFT;
                        ptel &= rcbits | ~(HPTE_R_R | HPTE_R_C);
                }
        }

        hpte[1] = ptel;

        /* Write the first HPTE dword, unlocking the HPTE and making it valid */
        eieio();
        hpte[0] = pteh;
        asm volatile("ptesync" : : : "memory");

        *pte_idx_ret = pte_index;
        return H_SUCCESS;
}
EXPORT_SYMBOL_GPL(kvmppc_do_h_enter);

long kvmppc_h_enter(struct kvm_vcpu *vcpu, unsigned long flags,
                    long pte_index, unsigned long pteh, unsigned long ptel)
{
        return kvmppc_do_h_enter(vcpu->kvm, flags, pte_index, pteh, ptel,
                                 vcpu->arch.pgdir, true, &vcpu->arch.gpr[4]);
}

#define LOCK_TOKEN      (*(u32 *)(&get_paca()->lock_token))

static inline int try_lock_tlbie(unsigned int *lock)
{
        unsigned int tmp, old;
        unsigned int token = LOCK_TOKEN;

        asm volatile("1:lwarx   %1,0,%2\n"
                     "  cmpwi   cr0,%1,0\n"
                     "  bne     2f\n"
                     "  stwcx.  %3,0,%2\n"
                     "  bne-    1b\n"
                     "  isync\n"
                     "2:"
                     : "=&r" (tmp), "=&r" (old)
                     : "r" (lock), "r" (token)
                     : "cc", "memory");
        return old == 0;
}

long kvmppc_do_h_remove(struct kvm *kvm, unsigned long flags,
                        unsigned long pte_index, unsigned long avpn,
                        unsigned long *hpret)
{
        unsigned long *hpte;
        unsigned long v, r, rb;
        struct revmap_entry *rev;

        if (pte_index >= kvm->arch.hpt_npte)
                return H_PARAMETER;
        hpte = (unsigned long *)(kvm->arch.hpt_virt + (pte_index << 4));
        while (!try_lock_hpte(hpte, HPTE_V_HVLOCK))
                cpu_relax();
        if ((hpte[0] & (HPTE_V_ABSENT | HPTE_V_VALID)) == 0 ||
            ((flags & H_AVPN) && (hpte[0] & ~0x7fUL) != avpn) ||
            ((flags & H_ANDCOND) && (hpte[0] & avpn) != 0)) {
                hpte[0] &= ~HPTE_V_HVLOCK;
                return H_NOT_FOUND;
        }

        rev = real_vmalloc_addr(&kvm->arch.revmap[pte_index]);
        v = hpte[0] & ~HPTE_V_HVLOCK;
        if (v & HPTE_V_VALID) {
                hpte[0] &= ~HPTE_V_VALID;
                rb = compute_tlbie_rb(v, hpte[1], pte_index);
                if (global_invalidates(kvm, flags)) {
                        while (!try_lock_tlbie(&kvm->arch.tlbie_lock))
                                cpu_relax();
                        asm volatile("ptesync" : : : "memory");
                        asm volatile(PPC_TLBIE(%1,%0)"; eieio; tlbsync"
                                     : : "r" (rb), "r" (kvm->arch.lpid));
                        asm volatile("ptesync" : : : "memory");
                        kvm->arch.tlbie_lock = 0;
                } else {
                        asm volatile("ptesync" : : : "memory");
                        asm volatile("tlbiel %0" : : "r" (rb));
                        asm volatile("ptesync" : : : "memory");
                }
                /* Read PTE low word after tlbie to get final R/C values */
                remove_revmap_chain(kvm, pte_index, rev, v, hpte[1]);
        }
        r = rev->guest_rpte & ~HPTE_GR_RESERVED;
        note_hpte_modification(kvm, rev);
        unlock_hpte(hpte, 0);

        hpret[0] = v;
        hpret[1] = r;
        return H_SUCCESS;
}
EXPORT_SYMBOL_GPL(kvmppc_do_h_remove);

long kvmppc_h_remove(struct kvm_vcpu *vcpu, unsigned long flags,
                     unsigned long pte_index, unsigned long avpn)
{
        return kvmppc_do_h_remove(vcpu->kvm, flags, pte_index, avpn,
                                  &vcpu->arch.gpr[4]);
}

long kvmppc_h_bulk_remove(struct kvm_vcpu *vcpu)
{
        struct kvm *kvm = vcpu->kvm;
        unsigned long *args = &vcpu->arch.gpr[4];
        unsigned long *hp, *hptes[4], tlbrb[4];
        long int i, j, k, n, found, indexes[4];
        unsigned long flags, req, pte_index, rcbits;
        long int local = 0;
        long int ret = H_SUCCESS;
        struct revmap_entry *rev, *revs[4];

        if (atomic_read(&kvm->online_vcpus) == 1)
                local = 1;
        for (i = 0; i < 4 && ret == H_SUCCESS; ) {
                n = 0;
                for (; i < 4; ++i) {
                        j = i * 2;
                        pte_index = args[j];
                        flags = pte_index >> 56;
                        pte_index &= ((1ul << 56) - 1);
                        req = flags >> 6;
                        flags &= 3;
                        if (req == 3) {         /* no more requests */
                                i = 4;
                                break;
                        }
                        if (req != 1 || flags == 3 ||
                            pte_index >= kvm->arch.hpt_npte) {
                                /* parameter error */
                                args[j] = ((0xa0 | flags) << 56) + pte_index;
                                ret = H_PARAMETER;
                                break;
                        }
                        hp = (unsigned long *)
                                (kvm->arch.hpt_virt + (pte_index << 4));
                        /* to avoid deadlock, don't spin except for first */
                        if (!try_lock_hpte(hp, HPTE_V_HVLOCK)) {
                                if (n)
                                        break;
                                while (!try_lock_hpte(hp, HPTE_V_HVLOCK))
                                        cpu_relax();
                        }
                        found = 0;
                        if (hp[0] & (HPTE_V_ABSENT | HPTE_V_VALID)) {
                                switch (flags & 3) {
                                case 0:         /* absolute */
                                        found = 1;
                                        break;
                                case 1:         /* andcond */
                                        if (!(hp[0] & args[j + 1]))
                                                found = 1;
                                        break;
                                case 2:         /* AVPN */
                                        if ((hp[0] & ~0x7fUL) == args[j + 1])
                                                found = 1;
                                        break;
                                }
                        }
                        if (!found) {
                                hp[0] &= ~HPTE_V_HVLOCK;
                                args[j] = ((0x90 | flags) << 56) + pte_index;
                                continue;
                        }

                        args[j] = ((0x80 | flags) << 56) + pte_index;
                        rev = real_vmalloc_addr(&kvm->arch.revmap[pte_index]);
                        note_hpte_modification(kvm, rev);

                        if (!(hp[0] & HPTE_V_VALID)) {
                                /* insert R and C bits from PTE */
                                rcbits = rev->guest_rpte & (HPTE_R_R|HPTE_R_C);
                                args[j] |= rcbits << (56 - 5);
                                hp[0] = 0;
                                continue;
                        }

                        hp[0] &= ~HPTE_V_VALID;         /* leave it locked */
                        tlbrb[n] = compute_tlbie_rb(hp[0], hp[1], pte_index);
                        indexes[n] = j;
                        hptes[n] = hp;
                        revs[n] = rev;
                        ++n;
                }

                if (!n)
                        break;

                /* Now that we've collected a batch, do the tlbies */
                if (!local) {
                        while(!try_lock_tlbie(&kvm->arch.tlbie_lock))
                                cpu_relax();
                        asm volatile("ptesync" : : : "memory");
                        for (k = 0; k < n; ++k)
                                asm volatile(PPC_TLBIE(%1,%0) : :
                                             "r" (tlbrb[k]),
                                             "r" (kvm->arch.lpid));
                        asm volatile("eieio; tlbsync; ptesync" : : : "memory");
                        kvm->arch.tlbie_lock = 0;
                } else {
                        asm volatile("ptesync" : : : "memory");
                        for (k = 0; k < n; ++k)
                                asm volatile("tlbiel %0" : : "r" (tlbrb[k]));
                        asm volatile("ptesync" : : : "memory");
                }

                /* Read PTE low words after tlbie to get final R/C values */
                for (k = 0; k < n; ++k) {
                        j = indexes[k];
                        pte_index = args[j] & ((1ul << 56) - 1);
                        hp = hptes[k];
                        rev = revs[k];
                        remove_revmap_chain(kvm, pte_index, rev, hp[0], hp[1]);
                        rcbits = rev->guest_rpte & (HPTE_R_R|HPTE_R_C);
                        args[j] |= rcbits << (56 - 5);
                        hp[0] = 0;
                }
        }

        return ret;
}

long kvmppc_h_protect(struct kvm_vcpu *vcpu, unsigned long flags,
                      unsigned long pte_index, unsigned long avpn,
                      unsigned long va)
{
        struct kvm *kvm = vcpu->kvm;
        unsigned long *hpte;
        struct revmap_entry *rev;
        unsigned long v, r, rb, mask, bits;

        if (pte_index >= kvm->arch.hpt_npte)
                return H_PARAMETER;

        hpte = (unsigned long *)(kvm->arch.hpt_virt + (pte_index << 4));
        while (!try_lock_hpte(hpte, HPTE_V_HVLOCK))
                cpu_relax();
        if ((hpte[0] & (HPTE_V_ABSENT | HPTE_V_VALID)) == 0 ||
            ((flags & H_AVPN) && (hpte[0] & ~0x7fUL) != avpn)) {
                hpte[0] &= ~HPTE_V_HVLOCK;
                return H_NOT_FOUND;
        }

        v = hpte[0];
        bits = (flags << 55) & HPTE_R_PP0;
        bits |= (flags << 48) & HPTE_R_KEY_HI;
        bits |= flags & (HPTE_R_PP | HPTE_R_N | HPTE_R_KEY_LO);

        /* Update guest view of 2nd HPTE dword */
        mask = HPTE_R_PP0 | HPTE_R_PP | HPTE_R_N |
                HPTE_R_KEY_HI | HPTE_R_KEY_LO;
        rev = real_vmalloc_addr(&kvm->arch.revmap[pte_index]);
        if (rev) {
                r = (rev->guest_rpte & ~mask) | bits;
                rev->guest_rpte = r;
                note_hpte_modification(kvm, rev);
        }
        r = (hpte[1] & ~mask) | bits;

        /* Update HPTE */
        if (v & HPTE_V_VALID) {
                rb = compute_tlbie_rb(v, r, pte_index);
                hpte[0] = v & ~HPTE_V_VALID;
                if (global_invalidates(kvm, flags)) {
                        while(!try_lock_tlbie(&kvm->arch.tlbie_lock))
                                cpu_relax();
                        asm volatile("ptesync" : : : "memory");
                        asm volatile(PPC_TLBIE(%1,%0)"; eieio; tlbsync"
                                     : : "r" (rb), "r" (kvm->arch.lpid));
                        asm volatile("ptesync" : : : "memory");
                        kvm->arch.tlbie_lock = 0;
                } else {
                        asm volatile("ptesync" : : : "memory");
                        asm volatile("tlbiel %0" : : "r" (rb));
                        asm volatile("ptesync" : : : "memory");
                }
                /*
                 * If the host has this page as readonly but the guest
                 * wants to make it read/write, reduce the permissions.
                 * Checking the host permissions involves finding the
                 * memslot and then the Linux PTE for the page.
                 */
                if (hpte_is_writable(r) && kvm->arch.using_mmu_notifiers) {
                        unsigned long psize, gfn, hva;
                        struct kvm_memory_slot *memslot;
                        pgd_t *pgdir = vcpu->arch.pgdir;
                        pte_t pte;

                        psize = hpte_page_size(v, r);
                        gfn = ((r & HPTE_R_RPN) & ~(psize - 1)) >> PAGE_SHIFT;
                        memslot = __gfn_to_memslot(kvm_memslots(kvm), gfn);
                        if (memslot) {
                                hva = __gfn_to_hva_memslot(memslot, gfn);
                                pte = lookup_linux_pte(pgdir, hva, 1, &psize);
                                if (pte_present(pte) && !pte_write(pte))
                                        r = hpte_make_readonly(r);
                        }
                }
        }
        hpte[1] = r;
        eieio();
        hpte[0] = v & ~HPTE_V_HVLOCK;
        asm volatile("ptesync" : : : "memory");
        return H_SUCCESS;
}

long kvmppc_h_read(struct kvm_vcpu *vcpu, unsigned long flags,
                   unsigned long pte_index)
{
        struct kvm *kvm = vcpu->kvm;
        unsigned long *hpte, v, r;
        int i, n = 1;
        struct revmap_entry *rev = NULL;

        if (pte_index >= kvm->arch.hpt_npte)
                return H_PARAMETER;
        if (flags & H_READ_4) {
                pte_index &= ~3;
                n = 4;
        }
        rev = real_vmalloc_addr(&kvm->arch.revmap[pte_index]);
        for (i = 0; i < n; ++i, ++pte_index) {
                hpte = (unsigned long *)(kvm->arch.hpt_virt + (pte_index << 4));
                v = hpte[0] & ~HPTE_V_HVLOCK;
                r = hpte[1];
                if (v & HPTE_V_ABSENT) {
                        v &= ~HPTE_V_ABSENT;
                        v |= HPTE_V_VALID;
                }
                if (v & HPTE_V_VALID) {
                        r = rev[i].guest_rpte | (r & (HPTE_R_R | HPTE_R_C));
                        r &= ~HPTE_GR_RESERVED;
                }
                vcpu->arch.gpr[4 + i * 2] = v;
                vcpu->arch.gpr[5 + i * 2] = r;
        }
        return H_SUCCESS;
}

void kvmppc_invalidate_hpte(struct kvm *kvm, unsigned long *hptep,
                        unsigned long pte_index)
{
        unsigned long rb;

        hptep[0] &= ~HPTE_V_VALID;
        rb = compute_tlbie_rb(hptep[0], hptep[1], pte_index);
        while (!try_lock_tlbie(&kvm->arch.tlbie_lock))
                cpu_relax();
        asm volatile("ptesync" : : : "memory");
        asm volatile(PPC_TLBIE(%1,%0)"; eieio; tlbsync"
                     : : "r" (rb), "r" (kvm->arch.lpid));
        asm volatile("ptesync" : : : "memory");
        kvm->arch.tlbie_lock = 0;
}
EXPORT_SYMBOL_GPL(kvmppc_invalidate_hpte);

void kvmppc_clear_ref_hpte(struct kvm *kvm, unsigned long *hptep,
                           unsigned long pte_index)
{
        unsigned long rb;
        unsigned char rbyte;

        rb = compute_tlbie_rb(hptep[0], hptep[1], pte_index);
        rbyte = (hptep[1] & ~HPTE_R_R) >> 8;
        /* modify only the second-last byte, which contains the ref bit */
        *((char *)hptep + 14) = rbyte;
        while (!try_lock_tlbie(&kvm->arch.tlbie_lock))
                cpu_relax();
        asm volatile(PPC_TLBIE(%1,%0)"; eieio; tlbsync"
                     : : "r" (rb), "r" (kvm->arch.lpid));
        asm volatile("ptesync" : : : "memory");
        kvm->arch.tlbie_lock = 0;
}
EXPORT_SYMBOL_GPL(kvmppc_clear_ref_hpte);

static int slb_base_page_shift[4] = {
        24,     /* 16M */
        16,     /* 64k */
        34,     /* 16G */
        20,     /* 1M, unsupported */
};

long kvmppc_hv_find_lock_hpte(struct kvm *kvm, gva_t eaddr, unsigned long slb_v,
                              unsigned long valid)
{
        unsigned int i;
        unsigned int pshift;
        unsigned long somask;
        unsigned long vsid, hash;
        unsigned long avpn;
        unsigned long *hpte;
        unsigned long mask, val;
        unsigned long v, r;

        /* Get page shift, work out hash and AVPN etc. */
        mask = SLB_VSID_B | HPTE_V_AVPN | HPTE_V_SECONDARY;
        val = 0;
        pshift = 12;
        if (slb_v & SLB_VSID_L) {
                mask |= HPTE_V_LARGE;
                val |= HPTE_V_LARGE;
                pshift = slb_base_page_shift[(slb_v & SLB_VSID_LP) >> 4];
        }
        if (slb_v & SLB_VSID_B_1T) {
                somask = (1UL << 40) - 1;
                vsid = (slb_v & ~SLB_VSID_B) >> SLB_VSID_SHIFT_1T;
                vsid ^= vsid << 25;
        } else {
                somask = (1UL << 28) - 1;
                vsid = (slb_v & ~SLB_VSID_B) >> SLB_VSID_SHIFT;
        }
        hash = (vsid ^ ((eaddr & somask) >> pshift)) & kvm->arch.hpt_mask;
        avpn = slb_v & ~(somask >> 16); /* also includes B */
        avpn |= (eaddr & somask) >> 16;

        if (pshift >= 24)
                avpn &= ~((1UL << (pshift - 16)) - 1);
        else
                avpn &= ~0x7fUL;
        val |= avpn;

        for (;;) {
                hpte = (unsigned long *)(kvm->arch.hpt_virt + (hash << 7));

                for (i = 0; i < 16; i += 2) {
                        /* Read the PTE racily */
                        v = hpte[i] & ~HPTE_V_HVLOCK;

                        /* Check valid/absent, hash, segment size and AVPN */
                        if (!(v & valid) || (v & mask) != val)
                                continue;

                        /* Lock the PTE and read it under the lock */
                        while (!try_lock_hpte(&hpte[i], HPTE_V_HVLOCK))
                                cpu_relax();
                        v = hpte[i] & ~HPTE_V_HVLOCK;
                        r = hpte[i+1];

                        /*
                         * Check the HPTE again, including large page size
                         * Since we don't currently allow any MPSS (mixed
                         * page-size segment) page sizes, it is sufficient
                         * to check against the actual page size.
                         */
                        if ((v & valid) && (v & mask) == val &&
                            hpte_page_size(v, r) == (1ul << pshift))
                                /* Return with the HPTE still locked */
                                return (hash << 3) + (i >> 1);

                        /* Unlock and move on */
                        hpte[i] = v;
                }

                if (val & HPTE_V_SECONDARY)
                        break;
                val |= HPTE_V_SECONDARY;
                hash = hash ^ kvm->arch.hpt_mask;
        }
        return -1;
}
EXPORT_SYMBOL(kvmppc_hv_find_lock_hpte);

/*
 * Called in real mode to check whether an HPTE not found fault
 * is due to accessing a paged-out page or an emulated MMIO page,
 * or if a protection fault is due to accessing a page that the
 * guest wanted read/write access to but which we made read-only.
 * Returns a possibly modified status (DSISR) value if not
 * (i.e. pass the interrupt to the guest),
 * -1 to pass the fault up to host kernel mode code, -2 to do that
 * and also load the instruction word (for MMIO emulation),
 * or 0 if we should make the guest retry the access.
 */
long kvmppc_hpte_hv_fault(struct kvm_vcpu *vcpu, unsigned long addr,
                          unsigned long slb_v, unsigned int status, bool data)
{
        struct kvm *kvm = vcpu->kvm;
        long int index;
        unsigned long v, r, gr;
        unsigned long *hpte;
        unsigned long valid;
        struct revmap_entry *rev;
        unsigned long pp, key;

        /* For protection fault, expect to find a valid HPTE */
        valid = HPTE_V_VALID;
        if (status & DSISR_NOHPTE)
                valid |= HPTE_V_ABSENT;

        index = kvmppc_hv_find_lock_hpte(kvm, addr, slb_v, valid);
        if (index < 0) {
                if (status & DSISR_NOHPTE)
                        return status;  /* there really was no HPTE */
                return 0;               /* for prot fault, HPTE disappeared */
        }
        hpte = (unsigned long *)(kvm->arch.hpt_virt + (index << 4));
        v = hpte[0] & ~HPTE_V_HVLOCK;
        r = hpte[1];
        rev = real_vmalloc_addr(&kvm->arch.revmap[index]);
        gr = rev->guest_rpte;

        unlock_hpte(hpte, v);

        /* For not found, if the HPTE is valid by now, retry the instruction */
        if ((status & DSISR_NOHPTE) && (v & HPTE_V_VALID))
                return 0;

        /* Check access permissions to the page */
        pp = gr & (HPTE_R_PP0 | HPTE_R_PP);
        key = (vcpu->arch.shregs.msr & MSR_PR) ? SLB_VSID_KP : SLB_VSID_KS;
        status &= ~DSISR_NOHPTE;        /* DSISR_NOHPTE == SRR1_ISI_NOPT */
        if (!data) {
                if (gr & (HPTE_R_N | HPTE_R_G))
                        return status | SRR1_ISI_N_OR_G;
                if (!hpte_read_permission(pp, slb_v & key))
                        return status | SRR1_ISI_PROT;
        } else if (status & DSISR_ISSTORE) {
                /* check write permission */
                if (!hpte_write_permission(pp, slb_v & key))
                        return status | DSISR_PROTFAULT;
        } else {
                if (!hpte_read_permission(pp, slb_v & key))
                        return status | DSISR_PROTFAULT;
        }

        /* Check storage key, if applicable */
        if (data && (vcpu->arch.shregs.msr & MSR_DR)) {
                unsigned int perm = hpte_get_skey_perm(gr, vcpu->arch.amr);
                if (status & DSISR_ISSTORE)
                        perm >>= 1;
                if (perm & 1)
                        return status | DSISR_KEYFAULT;
        }

        /* Save HPTE info for virtual-mode handler */
        vcpu->arch.pgfault_addr = addr;
        vcpu->arch.pgfault_index = index;
        vcpu->arch.pgfault_hpte[0] = v;
        vcpu->arch.pgfault_hpte[1] = r;

        /* Check the storage key to see if it is possibly emulated MMIO */
        if (data && (vcpu->arch.shregs.msr & MSR_IR) &&
            (r & (HPTE_R_KEY_HI | HPTE_R_KEY_LO)) ==
            (HPTE_R_KEY_HI | HPTE_R_KEY_LO))
                return -2;      /* MMIO emulation - load instr word */

        return -1;              /* send fault up to host kernel mode */
}