arm/arm64: KVM: fix potential NULL dereference in user_mem_abort()

[deliverable/linux.git] / arch / arm / kvm / mmu.c

/*
 * Copyright (C) 2012 - Virtual Open Systems and Columbia University
 * Author: Christoffer Dall <c.dall@virtualopensystems.com>
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */

#include <linux/mman.h>
#include <linux/kvm_host.h>
#include <linux/io.h>
#include <linux/hugetlb.h>
#include <trace/events/kvm.h>
#include <asm/pgalloc.h>
#include <asm/cacheflush.h>
#include <asm/kvm_arm.h>
#include <asm/kvm_mmu.h>
#include <asm/kvm_mmio.h>
#include <asm/kvm_asm.h>
#include <asm/kvm_emulate.h>

#include "trace.h"

extern char  __hyp_idmap_text_start[], __hyp_idmap_text_end[];

static pgd_t *boot_hyp_pgd;
static pgd_t *hyp_pgd;
static DEFINE_MUTEX(kvm_hyp_pgd_mutex);

static void *init_bounce_page;
static unsigned long hyp_idmap_start;
static unsigned long hyp_idmap_end;
static phys_addr_t hyp_idmap_vector;

#define pgd_order get_order(PTRS_PER_PGD * sizeof(pgd_t))

#define kvm_pmd_huge(_x)        (pmd_huge(_x) || pmd_trans_huge(_x))

static void kvm_tlb_flush_vmid_ipa(struct kvm *kvm, phys_addr_t ipa)
{
        /*
         * This function also gets called when dealing with HYP page
         * tables. As HYP doesn't have an associated struct kvm (and
         * the HYP page tables are fairly static), we don't do
         * anything there.
         */
        if (kvm)
                kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, kvm, ipa);
}

static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
                                  int min, int max)
{
        void *page;

        BUG_ON(max > KVM_NR_MEM_OBJS);
        if (cache->nobjs >= min)
                return 0;
        while (cache->nobjs < max) {
                page = (void *)__get_free_page(PGALLOC_GFP);
                if (!page)
                        return -ENOMEM;
                cache->objects[cache->nobjs++] = page;
        }
        return 0;
}

static void mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc)
{
        while (mc->nobjs)
                free_page((unsigned long)mc->objects[--mc->nobjs]);
}

static void *mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc)
{
        void *p;

        BUG_ON(!mc || !mc->nobjs);
        p = mc->objects[--mc->nobjs];
        return p;
}

static void clear_pgd_entry(struct kvm *kvm, pgd_t *pgd, phys_addr_t addr)
{
        pud_t *pud_table __maybe_unused = pud_offset(pgd, 0);
        pgd_clear(pgd);
        kvm_tlb_flush_vmid_ipa(kvm, addr);
        pud_free(NULL, pud_table);
        put_page(virt_to_page(pgd));
}

static void clear_pud_entry(struct kvm *kvm, pud_t *pud, phys_addr_t addr)
{
        pmd_t *pmd_table = pmd_offset(pud, 0);
        VM_BUG_ON(pud_huge(*pud));
        pud_clear(pud);
        kvm_tlb_flush_vmid_ipa(kvm, addr);
        pmd_free(NULL, pmd_table);
        put_page(virt_to_page(pud));
}

static void clear_pmd_entry(struct kvm *kvm, pmd_t *pmd, phys_addr_t addr)
{
        pte_t *pte_table = pte_offset_kernel(pmd, 0);
        VM_BUG_ON(kvm_pmd_huge(*pmd));
        pmd_clear(pmd);
        kvm_tlb_flush_vmid_ipa(kvm, addr);
        pte_free_kernel(NULL, pte_table);
        put_page(virt_to_page(pmd));
}

static void unmap_ptes(struct kvm *kvm, pmd_t *pmd,
                       phys_addr_t addr, phys_addr_t end)
{
        phys_addr_t start_addr = addr;
        pte_t *pte, *start_pte;

        start_pte = pte = pte_offset_kernel(pmd, addr);
        do {
                if (!pte_none(*pte)) {
                        kvm_set_pte(pte, __pte(0));
                        put_page(virt_to_page(pte));
                        kvm_tlb_flush_vmid_ipa(kvm, addr);
                }
        } while (pte++, addr += PAGE_SIZE, addr != end);

        if (kvm_pte_table_empty(start_pte))
                clear_pmd_entry(kvm, pmd, start_addr);
}

static void unmap_pmds(struct kvm *kvm, pud_t *pud,
                       phys_addr_t addr, phys_addr_t end)
{
        phys_addr_t next, start_addr = addr;
        pmd_t *pmd, *start_pmd;

        start_pmd = pmd = pmd_offset(pud, addr);
        do {
                next = kvm_pmd_addr_end(addr, end);
                if (!pmd_none(*pmd)) {
                        if (kvm_pmd_huge(*pmd)) {
                                pmd_clear(pmd);
                                kvm_tlb_flush_vmid_ipa(kvm, addr);
                                put_page(virt_to_page(pmd));
                        } else {
                                unmap_ptes(kvm, pmd, addr, next);
                        }
                }
        } while (pmd++, addr = next, addr != end);

        if (kvm_pmd_table_empty(start_pmd))
                clear_pud_entry(kvm, pud, start_addr);
}

static void unmap_puds(struct kvm *kvm, pgd_t *pgd,
                       phys_addr_t addr, phys_addr_t end)
{
        phys_addr_t next, start_addr = addr;
        pud_t *pud, *start_pud;

        start_pud = pud = pud_offset(pgd, addr);
        do {
                next = kvm_pud_addr_end(addr, end);
                if (!pud_none(*pud)) {
                        if (pud_huge(*pud)) {
                                pud_clear(pud);
                                kvm_tlb_flush_vmid_ipa(kvm, addr);
                                put_page(virt_to_page(pud));
                        } else {
                                unmap_pmds(kvm, pud, addr, next);
                        }
                }
        } while (pud++, addr = next, addr != end);

        if (kvm_pud_table_empty(start_pud))
                clear_pgd_entry(kvm, pgd, start_addr);
}


static void unmap_range(struct kvm *kvm, pgd_t *pgdp,
                        phys_addr_t start, u64 size)
{
        pgd_t *pgd;
        phys_addr_t addr = start, end = start + size;
        phys_addr_t next;

        pgd = pgdp + pgd_index(addr);
        do {
                next = kvm_pgd_addr_end(addr, end);
                unmap_puds(kvm, pgd, addr, next);
        } while (pgd++, addr = next, addr != end);
}

static void stage2_flush_ptes(struct kvm *kvm, pmd_t *pmd,
                              phys_addr_t addr, phys_addr_t end)
{
        pte_t *pte;

        pte = pte_offset_kernel(pmd, addr);
        do {
                if (!pte_none(*pte)) {
                        hva_t hva = gfn_to_hva(kvm, addr >> PAGE_SHIFT);
                        kvm_flush_dcache_to_poc((void*)hva, PAGE_SIZE);
                }
        } while (pte++, addr += PAGE_SIZE, addr != end);
}

static void stage2_flush_pmds(struct kvm *kvm, pud_t *pud,
                              phys_addr_t addr, phys_addr_t end)
{
        pmd_t *pmd;
        phys_addr_t next;

        pmd = pmd_offset(pud, addr);
        do {
                next = kvm_pmd_addr_end(addr, end);
                if (!pmd_none(*pmd)) {
                        if (kvm_pmd_huge(*pmd)) {
                                hva_t hva = gfn_to_hva(kvm, addr >> PAGE_SHIFT);
                                kvm_flush_dcache_to_poc((void*)hva, PMD_SIZE);
                        } else {
                                stage2_flush_ptes(kvm, pmd, addr, next);
                        }
                }
        } while (pmd++, addr = next, addr != end);
}

static void stage2_flush_puds(struct kvm *kvm, pgd_t *pgd,
                              phys_addr_t addr, phys_addr_t end)
{
        pud_t *pud;
        phys_addr_t next;

        pud = pud_offset(pgd, addr);
        do {
                next = kvm_pud_addr_end(addr, end);
                if (!pud_none(*pud)) {
                        if (pud_huge(*pud)) {
                                hva_t hva = gfn_to_hva(kvm, addr >> PAGE_SHIFT);
                                kvm_flush_dcache_to_poc((void*)hva, PUD_SIZE);
                        } else {
                                stage2_flush_pmds(kvm, pud, addr, next);
                        }
                }
        } while (pud++, addr = next, addr != end);
}

static void stage2_flush_memslot(struct kvm *kvm,
                                 struct kvm_memory_slot *memslot)
{
        phys_addr_t addr = memslot->base_gfn << PAGE_SHIFT;
        phys_addr_t end = addr + PAGE_SIZE * memslot->npages;
        phys_addr_t next;
        pgd_t *pgd;

        pgd = kvm->arch.pgd + pgd_index(addr);
        do {
                next = kvm_pgd_addr_end(addr, end);
                stage2_flush_puds(kvm, pgd, addr, next);
        } while (pgd++, addr = next, addr != end);
}

/**
 * stage2_flush_vm - Invalidate cache for pages mapped in stage 2
 * @kvm: The struct kvm pointer
 *
 * Go through the stage 2 page tables and invalidate any cache lines
 * backing memory already mapped to the VM.
 */
void stage2_flush_vm(struct kvm *kvm)
{
        struct kvm_memslots *slots;
        struct kvm_memory_slot *memslot;
        int idx;

        idx = srcu_read_lock(&kvm->srcu);
        spin_lock(&kvm->mmu_lock);

        slots = kvm_memslots(kvm);
        kvm_for_each_memslot(memslot, slots)
                stage2_flush_memslot(kvm, memslot);

        spin_unlock(&kvm->mmu_lock);
        srcu_read_unlock(&kvm->srcu, idx);
}

/**
 * free_boot_hyp_pgd - free HYP boot page tables
 *
 * Free the HYP boot page tables. The bounce page is also freed.
 */
void free_boot_hyp_pgd(void)
{
        mutex_lock(&kvm_hyp_pgd_mutex);

        if (boot_hyp_pgd) {
                unmap_range(NULL, boot_hyp_pgd, hyp_idmap_start, PAGE_SIZE);
                unmap_range(NULL, boot_hyp_pgd, TRAMPOLINE_VA, PAGE_SIZE);
                free_pages((unsigned long)boot_hyp_pgd, pgd_order);
                boot_hyp_pgd = NULL;
        }

        if (hyp_pgd)
                unmap_range(NULL, hyp_pgd, TRAMPOLINE_VA, PAGE_SIZE);

        free_page((unsigned long)init_bounce_page);
        init_bounce_page = NULL;

        mutex_unlock(&kvm_hyp_pgd_mutex);
}

/**
 * free_hyp_pgds - free Hyp-mode page tables
 *
 * Assumes hyp_pgd is a page table used strictly in Hyp-mode and
 * therefore contains either mappings in the kernel memory area (above
 * PAGE_OFFSET), or device mappings in the vmalloc range (from
 * VMALLOC_START to VMALLOC_END).
 *
 * boot_hyp_pgd should only map two pages for the init code.
 */
void free_hyp_pgds(void)
{
        unsigned long addr;

        free_boot_hyp_pgd();

        mutex_lock(&kvm_hyp_pgd_mutex);

        if (hyp_pgd) {
                for (addr = PAGE_OFFSET; virt_addr_valid(addr); addr += PGDIR_SIZE)
                        unmap_range(NULL, hyp_pgd, KERN_TO_HYP(addr), PGDIR_SIZE);
                for (addr = VMALLOC_START; is_vmalloc_addr((void*)addr); addr += PGDIR_SIZE)
                        unmap_range(NULL, hyp_pgd, KERN_TO_HYP(addr), PGDIR_SIZE);

                free_pages((unsigned long)hyp_pgd, pgd_order);
                hyp_pgd = NULL;
        }

        mutex_unlock(&kvm_hyp_pgd_mutex);
}

static void create_hyp_pte_mappings(pmd_t *pmd, unsigned long start,
                                    unsigned long end, unsigned long pfn,
                                    pgprot_t prot)
{
        pte_t *pte;
        unsigned long addr;

        addr = start;
        do {
                pte = pte_offset_kernel(pmd, addr);
                kvm_set_pte(pte, pfn_pte(pfn, prot));
                get_page(virt_to_page(pte));
                kvm_flush_dcache_to_poc(pte, sizeof(*pte));
                pfn++;
        } while (addr += PAGE_SIZE, addr != end);
}

static int create_hyp_pmd_mappings(pud_t *pud, unsigned long start,
                                   unsigned long end, unsigned long pfn,
                                   pgprot_t prot)
{
        pmd_t *pmd;
        pte_t *pte;
        unsigned long addr, next;

        addr = start;
        do {
                pmd = pmd_offset(pud, addr);

                BUG_ON(pmd_sect(*pmd));

                if (pmd_none(*pmd)) {
                        pte = pte_alloc_one_kernel(NULL, addr);
                        if (!pte) {
                                kvm_err("Cannot allocate Hyp pte\n");
                                return -ENOMEM;
                        }
                        pmd_populate_kernel(NULL, pmd, pte);
                        get_page(virt_to_page(pmd));
                        kvm_flush_dcache_to_poc(pmd, sizeof(*pmd));
                }

                next = pmd_addr_end(addr, end);

                create_hyp_pte_mappings(pmd, addr, next, pfn, prot);
                pfn += (next - addr) >> PAGE_SHIFT;
        } while (addr = next, addr != end);

        return 0;
}

static int __create_hyp_mappings(pgd_t *pgdp,
                                 unsigned long start, unsigned long end,
                                 unsigned long pfn, pgprot_t prot)
{
        pgd_t *pgd;
        pud_t *pud;
        pmd_t *pmd;
        unsigned long addr, next;
        int err = 0;

        mutex_lock(&kvm_hyp_pgd_mutex);
        addr = start & PAGE_MASK;
        end = PAGE_ALIGN(end);
        do {
                pgd = pgdp + pgd_index(addr);
                pud = pud_offset(pgd, addr);

                if (pud_none_or_clear_bad(pud)) {
                        pmd = pmd_alloc_one(NULL, addr);
                        if (!pmd) {
                                kvm_err("Cannot allocate Hyp pmd\n");
                                err = -ENOMEM;
                                goto out;
                        }
                        pud_populate(NULL, pud, pmd);
                        get_page(virt_to_page(pud));
                        kvm_flush_dcache_to_poc(pud, sizeof(*pud));
                }

                next = pgd_addr_end(addr, end);
                err = create_hyp_pmd_mappings(pud, addr, next, pfn, prot);
                if (err)
                        goto out;
                pfn += (next - addr) >> PAGE_SHIFT;
        } while (addr = next, addr != end);
out:
        mutex_unlock(&kvm_hyp_pgd_mutex);
        return err;
}

static phys_addr_t kvm_kaddr_to_phys(void *kaddr)
{
        if (!is_vmalloc_addr(kaddr)) {
                BUG_ON(!virt_addr_valid(kaddr));
                return __pa(kaddr);
        } else {
                return page_to_phys(vmalloc_to_page(kaddr)) +
                       offset_in_page(kaddr);
        }
}

/**
 * create_hyp_mappings - duplicate a kernel virtual address range in Hyp mode
 * @from:       The virtual kernel start address of the range
 * @to:         The virtual kernel end address of the range (exclusive)
 *
 * The same virtual address as the kernel virtual address is also used
 * in Hyp-mode mapping (modulo HYP_PAGE_OFFSET) to the same underlying
 * physical pages.
 */
int create_hyp_mappings(void *from, void *to)
{
        phys_addr_t phys_addr;
        unsigned long virt_addr;
        unsigned long start = KERN_TO_HYP((unsigned long)from);
        unsigned long end = KERN_TO_HYP((unsigned long)to);

        start = start & PAGE_MASK;
        end = PAGE_ALIGN(end);

        for (virt_addr = start; virt_addr < end; virt_addr += PAGE_SIZE) {
                int err;

                phys_addr = kvm_kaddr_to_phys(from + virt_addr - start);
                err = __create_hyp_mappings(hyp_pgd, virt_addr,
                                            virt_addr + PAGE_SIZE,
                                            __phys_to_pfn(phys_addr),
                                            PAGE_HYP);
                if (err)
                        return err;
        }

        return 0;
}

/**
 * create_hyp_io_mappings - duplicate a kernel IO mapping into Hyp mode
 * @from:       The kernel start VA of the range
 * @to:         The kernel end VA of the range (exclusive)
 * @phys_addr:  The physical start address which gets mapped
 *
 * The resulting HYP VA is the same as the kernel VA, modulo
 * HYP_PAGE_OFFSET.
 */
int create_hyp_io_mappings(void *from, void *to, phys_addr_t phys_addr)
{
        unsigned long start = KERN_TO_HYP((unsigned long)from);
        unsigned long end = KERN_TO_HYP((unsigned long)to);

        /* Check for a valid kernel IO mapping */
        if (!is_vmalloc_addr(from) || !is_vmalloc_addr(to - 1))
                return -EINVAL;

        return __create_hyp_mappings(hyp_pgd, start, end,
                                     __phys_to_pfn(phys_addr), PAGE_HYP_DEVICE);
}

/**
 * kvm_alloc_stage2_pgd - allocate level-1 table for stage-2 translation.
 * @kvm:        The KVM struct pointer for the VM.
 *
 * Allocates the 1st level table only of size defined by S2_PGD_ORDER (can
 * support either full 40-bit input addresses or limited to 32-bit input
 * addresses). Clears the allocated pages.
 *
 * Note we don't need locking here as this is only called when the VM is
 * created, which can only be done once.
 */
int kvm_alloc_stage2_pgd(struct kvm *kvm)
{
        pgd_t *pgd;

        if (kvm->arch.pgd != NULL) {
                kvm_err("kvm_arch already initialized?\n");
                return -EINVAL;
        }

        pgd = (pgd_t *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, S2_PGD_ORDER);
        if (!pgd)
                return -ENOMEM;

        kvm_clean_pgd(pgd);
        kvm->arch.pgd = pgd;

        return 0;
}

/**
 * unmap_stage2_range -- Clear stage2 page table entries to unmap a range
 * @kvm:   The VM pointer
 * @start: The intermediate physical base address of the range to unmap
 * @size:  The size of the area to unmap
 *
 * Clear a range of stage-2 mappings, lowering the various ref-counts.  Must
 * be called while holding mmu_lock (unless for freeing the stage2 pgd before
 * destroying the VM), otherwise another faulting VCPU may come in and mess
 * with things behind our backs.
 */
static void unmap_stage2_range(struct kvm *kvm, phys_addr_t start, u64 size)
{
        unmap_range(kvm, kvm->arch.pgd, start, size);
}

/**
 * kvm_free_stage2_pgd - free all stage-2 tables
 * @kvm:        The KVM struct pointer for the VM.
 *
 * Walks the level-1 page table pointed to by kvm->arch.pgd and frees all
 * underlying level-2 and level-3 tables before freeing the actual level-1 table
 * and setting the struct pointer to NULL.
 *
 * Note we don't need locking here as this is only called when the VM is
 * destroyed, which can only be done once.
 */
void kvm_free_stage2_pgd(struct kvm *kvm)
{
        if (kvm->arch.pgd == NULL)
                return;

        unmap_stage2_range(kvm, 0, KVM_PHYS_SIZE);
        free_pages((unsigned long)kvm->arch.pgd, S2_PGD_ORDER);
        kvm->arch.pgd = NULL;
}

static pmd_t *stage2_get_pmd(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
                             phys_addr_t addr)
{
        pgd_t *pgd;
        pud_t *pud;
        pmd_t *pmd;

        pgd = kvm->arch.pgd + pgd_index(addr);
        pud = pud_offset(pgd, addr);
        if (pud_none(*pud)) {
                if (!cache)
                        return NULL;
                pmd = mmu_memory_cache_alloc(cache);
                pud_populate(NULL, pud, pmd);
                get_page(virt_to_page(pud));
        }

        return pmd_offset(pud, addr);
}

static int stage2_set_pmd_huge(struct kvm *kvm, struct kvm_mmu_memory_cache
                               *cache, phys_addr_t addr, const pmd_t *new_pmd)
{
        pmd_t *pmd, old_pmd;

        pmd = stage2_get_pmd(kvm, cache, addr);
        VM_BUG_ON(!pmd);

        /*
         * Mapping in huge pages should only happen through a fault.  If a
         * page is merged into a transparent huge page, the individual
         * subpages of that huge page should be unmapped through MMU
         * notifiers before we get here.
         *
         * Merging of CompoundPages is not supported; they should become
         * splitting first, unmapped, merged, and mapped back in on-demand.
         */
        VM_BUG_ON(pmd_present(*pmd) && pmd_pfn(*pmd) != pmd_pfn(*new_pmd));

        old_pmd = *pmd;
        kvm_set_pmd(pmd, *new_pmd);
        if (pmd_present(old_pmd))
                kvm_tlb_flush_vmid_ipa(kvm, addr);
        else
                get_page(virt_to_page(pmd));
        return 0;
}

static int stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
                          phys_addr_t addr, const pte_t *new_pte, bool iomap)
{
        pmd_t *pmd;
        pte_t *pte, old_pte;

        /* Create stage-2 page table mapping - Level 1 */
        pmd = stage2_get_pmd(kvm, cache, addr);
        if (!pmd) {
                /*
                 * Ignore calls from kvm_set_spte_hva for unallocated
                 * address ranges.
                 */
                return 0;
        }

        /* Create stage-2 page mappings - Level 2 */
        if (pmd_none(*pmd)) {
                if (!cache)
                        return 0; /* ignore calls from kvm_set_spte_hva */
                pte = mmu_memory_cache_alloc(cache);
                kvm_clean_pte(pte);
                pmd_populate_kernel(NULL, pmd, pte);
                get_page(virt_to_page(pmd));
        }

        pte = pte_offset_kernel(pmd, addr);

        if (iomap && pte_present(*pte))
                return -EFAULT;

        /* Create 2nd stage page table mapping - Level 3 */
        old_pte = *pte;
        kvm_set_pte(pte, *new_pte);
        if (pte_present(old_pte))
                kvm_tlb_flush_vmid_ipa(kvm, addr);
        else
                get_page(virt_to_page(pte));

        return 0;
}

/**
 * kvm_phys_addr_ioremap - map a device range to guest IPA
 *
 * @kvm:        The KVM pointer
 * @guest_ipa:  The IPA at which to insert the mapping
 * @pa:         The physical address of the device
 * @size:       The size of the mapping
 */
int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
                          phys_addr_t pa, unsigned long size)
{
        phys_addr_t addr, end;
        int ret = 0;
        unsigned long pfn;
        struct kvm_mmu_memory_cache cache = { 0, };

        end = (guest_ipa + size + PAGE_SIZE - 1) & PAGE_MASK;
        pfn = __phys_to_pfn(pa);

        for (addr = guest_ipa; addr < end; addr += PAGE_SIZE) {
                pte_t pte = pfn_pte(pfn, PAGE_S2_DEVICE);

                ret = mmu_topup_memory_cache(&cache, 2, 2);
                if (ret)
                        goto out;
                spin_lock(&kvm->mmu_lock);
                ret = stage2_set_pte(kvm, &cache, addr, &pte, true);
                spin_unlock(&kvm->mmu_lock);
                if (ret)
                        goto out;

                pfn++;
        }

out:
        mmu_free_memory_cache(&cache);
        return ret;
}

static bool transparent_hugepage_adjust(pfn_t *pfnp, phys_addr_t *ipap)
{
        pfn_t pfn = *pfnp;
        gfn_t gfn = *ipap >> PAGE_SHIFT;

        if (PageTransCompound(pfn_to_page(pfn))) {
                unsigned long mask;
                /*
                 * The address we faulted on is backed by a transparent huge
                 * page.  However, because we map the compound huge page and
                 * not the individual tail page, we need to transfer the
                 * refcount to the head page.  We have to be careful that the
                 * THP doesn't start to split while we are adjusting the
                 * refcounts.
                 *
                 * We are sure this doesn't happen, because mmu_notifier_retry
                 * was successful and we are holding the mmu_lock, so if this
                 * THP is trying to split, it will be blocked in the mmu
                 * notifier before touching any of the pages, specifically
                 * before being able to call __split_huge_page_refcount().
                 *
                 * We can therefore safely transfer the refcount from PG_tail
                 * to PG_head and switch the pfn from a tail page to the head
                 * page accordingly.
                 */
                mask = PTRS_PER_PMD - 1;
                VM_BUG_ON((gfn & mask) != (pfn & mask));
                if (pfn & mask) {
                        *ipap &= PMD_MASK;
                        kvm_release_pfn_clean(pfn);
                        pfn &= ~mask;
                        kvm_get_pfn(pfn);
                        *pfnp = pfn;
                }

                return true;
        }

        return false;
}

static bool kvm_is_write_fault(struct kvm_vcpu *vcpu)
{
        if (kvm_vcpu_trap_is_iabt(vcpu))
                return false;

        return kvm_vcpu_dabt_iswrite(vcpu);
}

static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
                          struct kvm_memory_slot *memslot, unsigned long hva,
                          unsigned long fault_status)
{
        int ret;
        bool write_fault, writable, hugetlb = false, force_pte = false;
        unsigned long mmu_seq;
        gfn_t gfn = fault_ipa >> PAGE_SHIFT;
        struct kvm *kvm = vcpu->kvm;
        struct kvm_mmu_memory_cache *memcache = &vcpu->arch.mmu_page_cache;
        struct vm_area_struct *vma;
        pfn_t pfn;
        pgprot_t mem_type = PAGE_S2;

        write_fault = kvm_is_write_fault(vcpu);
        if (fault_status == FSC_PERM && !write_fault) {
                kvm_err("Unexpected L2 read permission error\n");
                return -EFAULT;
        }

        /* Let's check if we will get back a huge page backed by hugetlbfs */
        down_read(&current->mm->mmap_sem);
        vma = find_vma_intersection(current->mm, hva, hva + 1);
        if (unlikely(!vma)) {
                kvm_err("Failed to find VMA for hva 0x%lx\n", hva);
                up_read(&current->mm->mmap_sem);
                return -EFAULT;
        }

        if (is_vm_hugetlb_page(vma)) {
                hugetlb = true;
                gfn = (fault_ipa & PMD_MASK) >> PAGE_SHIFT;
        } else {
                /*
                 * Pages belonging to memslots that don't have the same
                 * alignment for userspace and IPA cannot be mapped using
                 * block descriptors even if the pages belong to a THP for
                 * the process, because the stage-2 block descriptor will
                 * cover more than a single THP and we loose atomicity for
                 * unmapping, updates, and splits of the THP or other pages
                 * in the stage-2 block range.
                 */
                if ((memslot->userspace_addr & ~PMD_MASK) !=
                    ((memslot->base_gfn << PAGE_SHIFT) & ~PMD_MASK))
                        force_pte = true;
        }
        up_read(&current->mm->mmap_sem);

        /* We need minimum second+third level pages */
        ret = mmu_topup_memory_cache(memcache, 2, KVM_NR_MEM_OBJS);
        if (ret)
                return ret;

        mmu_seq = vcpu->kvm->mmu_notifier_seq;
        /*
         * Ensure the read of mmu_notifier_seq happens before we call
         * gfn_to_pfn_prot (which calls get_user_pages), so that we don't risk
         * the page we just got a reference to gets unmapped before we have a
         * chance to grab the mmu_lock, which ensure that if the page gets
         * unmapped afterwards, the call to kvm_unmap_hva will take it away
         * from us again properly. This smp_rmb() interacts with the smp_wmb()
         * in kvm_mmu_notifier_invalidate_<page|range_end>.
         */
        smp_rmb();

        pfn = gfn_to_pfn_prot(kvm, gfn, write_fault, &writable);
        if (is_error_pfn(pfn))
                return -EFAULT;

        if (kvm_is_mmio_pfn(pfn))
                mem_type = PAGE_S2_DEVICE;

        spin_lock(&kvm->mmu_lock);
        if (mmu_notifier_retry(kvm, mmu_seq))
                goto out_unlock;
        if (!hugetlb && !force_pte)
                hugetlb = transparent_hugepage_adjust(&pfn, &fault_ipa);

        if (hugetlb) {
                pmd_t new_pmd = pfn_pmd(pfn, mem_type);
                new_pmd = pmd_mkhuge(new_pmd);
                if (writable) {
                        kvm_set_s2pmd_writable(&new_pmd);
                        kvm_set_pfn_dirty(pfn);
                }
                coherent_cache_guest_page(vcpu, hva & PMD_MASK, PMD_SIZE);
                ret = stage2_set_pmd_huge(kvm, memcache, fault_ipa, &new_pmd);
        } else {
                pte_t new_pte = pfn_pte(pfn, mem_type);
                if (writable) {
                        kvm_set_s2pte_writable(&new_pte);
                        kvm_set_pfn_dirty(pfn);
                }
                coherent_cache_guest_page(vcpu, hva, PAGE_SIZE);
                ret = stage2_set_pte(kvm, memcache, fault_ipa, &new_pte,
                                     mem_type == PAGE_S2_DEVICE);
        }


out_unlock:
        spin_unlock(&kvm->mmu_lock);
        kvm_release_pfn_clean(pfn);
        return ret;
}

/**
 * kvm_handle_guest_abort - handles all 2nd stage aborts
 * @vcpu:       the VCPU pointer
 * @run:        the kvm_run structure
 *
 * Any abort that gets to the host is almost guaranteed to be caused by a
 * missing second stage translation table entry, which can mean that either the
 * guest simply needs more memory and we must allocate an appropriate page or it
 * can mean that the guest tried to access I/O memory, which is emulated by user
 * space. The distinction is based on the IPA causing the fault and whether this
 * memory region has been registered as standard RAM by user space.
 */
int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
        unsigned long fault_status;
        phys_addr_t fault_ipa;
        struct kvm_memory_slot *memslot;
        unsigned long hva;
        bool is_iabt, write_fault, writable;
        gfn_t gfn;
        int ret, idx;

        is_iabt = kvm_vcpu_trap_is_iabt(vcpu);
        fault_ipa = kvm_vcpu_get_fault_ipa(vcpu);

        trace_kvm_guest_fault(*vcpu_pc(vcpu), kvm_vcpu_get_hsr(vcpu),
                              kvm_vcpu_get_hfar(vcpu), fault_ipa);

        /* Check the stage-2 fault is trans. fault or write fault */
        fault_status = kvm_vcpu_trap_get_fault_type(vcpu);
        if (fault_status != FSC_FAULT && fault_status != FSC_PERM) {
                kvm_err("Unsupported FSC: EC=%#x xFSC=%#lx ESR_EL2=%#lx\n",
                        kvm_vcpu_trap_get_class(vcpu),
                        (unsigned long)kvm_vcpu_trap_get_fault(vcpu),
                        (unsigned long)kvm_vcpu_get_hsr(vcpu));
                return -EFAULT;
        }

        idx = srcu_read_lock(&vcpu->kvm->srcu);

        gfn = fault_ipa >> PAGE_SHIFT;
        memslot = gfn_to_memslot(vcpu->kvm, gfn);
        hva = gfn_to_hva_memslot_prot(memslot, gfn, &writable);
        write_fault = kvm_is_write_fault(vcpu);
        if (kvm_is_error_hva(hva) || (write_fault && !writable)) {
                if (is_iabt) {
                        /* Prefetch Abort on I/O address */
                        kvm_inject_pabt(vcpu, kvm_vcpu_get_hfar(vcpu));
                        ret = 1;
                        goto out_unlock;
                }

                /*
                 * The IPA is reported as [MAX:12], so we need to
                 * complement it with the bottom 12 bits from the
                 * faulting VA. This is always 12 bits, irrespective
                 * of the page size.
                 */
                fault_ipa |= kvm_vcpu_get_hfar(vcpu) & ((1 << 12) - 1);
                ret = io_mem_abort(vcpu, run, fault_ipa);
                goto out_unlock;
        }

        ret = user_mem_abort(vcpu, fault_ipa, memslot, hva, fault_status);
        if (ret == 0)
                ret = 1;
out_unlock:
        srcu_read_unlock(&vcpu->kvm->srcu, idx);
        return ret;
}

static void handle_hva_to_gpa(struct kvm *kvm,
                              unsigned long start,
                              unsigned long end,
                              void (*handler)(struct kvm *kvm,
                                              gpa_t gpa, void *data),
                              void *data)
{
        struct kvm_memslots *slots;
        struct kvm_memory_slot *memslot;

        slots = kvm_memslots(kvm);

        /* we only care about the pages that the guest sees */
        kvm_for_each_memslot(memslot, slots) {
                unsigned long hva_start, hva_end;
                gfn_t gfn, gfn_end;

                hva_start = max(start, memslot->userspace_addr);
                hva_end = min(end, memslot->userspace_addr +
                                        (memslot->npages << PAGE_SHIFT));
                if (hva_start >= hva_end)
                        continue;

                /*
                 * {gfn(page) | page intersects with [hva_start, hva_end)} =
                 * {gfn_start, gfn_start+1, ..., gfn_end-1}.
                 */
                gfn = hva_to_gfn_memslot(hva_start, memslot);
                gfn_end = hva_to_gfn_memslot(hva_end + PAGE_SIZE - 1, memslot);

                for (; gfn < gfn_end; ++gfn) {
                        gpa_t gpa = gfn << PAGE_SHIFT;
                        handler(kvm, gpa, data);
                }
        }
}

static void kvm_unmap_hva_handler(struct kvm *kvm, gpa_t gpa, void *data)
{
        unmap_stage2_range(kvm, gpa, PAGE_SIZE);
}

int kvm_unmap_hva(struct kvm *kvm, unsigned long hva)
{
        unsigned long end = hva + PAGE_SIZE;

        if (!kvm->arch.pgd)
                return 0;

        trace_kvm_unmap_hva(hva);
        handle_hva_to_gpa(kvm, hva, end, &kvm_unmap_hva_handler, NULL);
        return 0;
}

int kvm_unmap_hva_range(struct kvm *kvm,
                        unsigned long start, unsigned long end)
{
        if (!kvm->arch.pgd)
                return 0;

        trace_kvm_unmap_hva_range(start, end);
        handle_hva_to_gpa(kvm, start, end, &kvm_unmap_hva_handler, NULL);
        return 0;
}

static void kvm_set_spte_handler(struct kvm *kvm, gpa_t gpa, void *data)
{
        pte_t *pte = (pte_t *)data;

        stage2_set_pte(kvm, NULL, gpa, pte, false);
}


void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte)
{
        unsigned long end = hva + PAGE_SIZE;
        pte_t stage2_pte;

        if (!kvm->arch.pgd)
                return;

        trace_kvm_set_spte_hva(hva);
        stage2_pte = pfn_pte(pte_pfn(pte), PAGE_S2);
        handle_hva_to_gpa(kvm, hva, end, &kvm_set_spte_handler, &stage2_pte);
}

void kvm_mmu_free_memory_caches(struct kvm_vcpu *vcpu)
{
        mmu_free_memory_cache(&vcpu->arch.mmu_page_cache);
}

phys_addr_t kvm_mmu_get_httbr(void)
{
        return virt_to_phys(hyp_pgd);
}

phys_addr_t kvm_mmu_get_boot_httbr(void)
{
        return virt_to_phys(boot_hyp_pgd);
}

phys_addr_t kvm_get_idmap_vector(void)
{
        return hyp_idmap_vector;
}

int kvm_mmu_init(void)
{
        int err;

        hyp_idmap_start = kvm_virt_to_phys(__hyp_idmap_text_start);
        hyp_idmap_end = kvm_virt_to_phys(__hyp_idmap_text_end);
        hyp_idmap_vector = kvm_virt_to_phys(__kvm_hyp_init);

        if ((hyp_idmap_start ^ hyp_idmap_end) & PAGE_MASK) {
                /*
                 * Our init code is crossing a page boundary. Allocate
                 * a bounce page, copy the code over and use that.
                 */
                size_t len = __hyp_idmap_text_end - __hyp_idmap_text_start;
                phys_addr_t phys_base;

                init_bounce_page = (void *)__get_free_page(GFP_KERNEL);
                if (!init_bounce_page) {
                        kvm_err("Couldn't allocate HYP init bounce page\n");
                        err = -ENOMEM;
                        goto out;
                }

                memcpy(init_bounce_page, __hyp_idmap_text_start, len);
                /*
                 * Warning: the code we just copied to the bounce page
                 * must be flushed to the point of coherency.
                 * Otherwise, the data may be sitting in L2, and HYP
                 * mode won't be able to observe it as it runs with
                 * caches off at that point.
                 */
                kvm_flush_dcache_to_poc(init_bounce_page, len);

                phys_base = kvm_virt_to_phys(init_bounce_page);
                hyp_idmap_vector += phys_base - hyp_idmap_start;
                hyp_idmap_start = phys_base;
                hyp_idmap_end = phys_base + len;

                kvm_info("Using HYP init bounce page @%lx\n",
                         (unsigned long)phys_base);
        }

        hyp_pgd = (pgd_t *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, pgd_order);
        boot_hyp_pgd = (pgd_t *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, pgd_order);

        if (!hyp_pgd || !boot_hyp_pgd) {
                kvm_err("Hyp mode PGD not allocated\n");
                err = -ENOMEM;
                goto out;
        }

        /* Create the idmap in the boot page tables */
        err =   __create_hyp_mappings(boot_hyp_pgd,
                                      hyp_idmap_start, hyp_idmap_end,
                                      __phys_to_pfn(hyp_idmap_start),
                                      PAGE_HYP);

        if (err) {
                kvm_err("Failed to idmap %lx-%lx\n",
                        hyp_idmap_start, hyp_idmap_end);
                goto out;
        }

        /* Map the very same page at the trampoline VA */
        err =   __create_hyp_mappings(boot_hyp_pgd,
                                      TRAMPOLINE_VA, TRAMPOLINE_VA + PAGE_SIZE,
                                      __phys_to_pfn(hyp_idmap_start),
                                      PAGE_HYP);
        if (err) {
                kvm_err("Failed to map trampoline @%lx into boot HYP pgd\n",
                        TRAMPOLINE_VA);
                goto out;
        }

        /* Map the same page again into the runtime page tables */
        err =   __create_hyp_mappings(hyp_pgd,
                                      TRAMPOLINE_VA, TRAMPOLINE_VA + PAGE_SIZE,
                                      __phys_to_pfn(hyp_idmap_start),
                                      PAGE_HYP);
        if (err) {
                kvm_err("Failed to map trampoline @%lx into runtime HYP pgd\n",
                        TRAMPOLINE_VA);
                goto out;
        }

        return 0;
out:
        free_hyp_pgds();
        return err;
}

void kvm_arch_commit_memory_region(struct kvm *kvm,
                                   struct kvm_userspace_memory_region *mem,
                                   const struct kvm_memory_slot *old,
                                   enum kvm_mr_change change)
{
        gpa_t gpa = old->base_gfn << PAGE_SHIFT;
        phys_addr_t size = old->npages << PAGE_SHIFT;
        if (change == KVM_MR_DELETE || change == KVM_MR_MOVE) {
                spin_lock(&kvm->mmu_lock);
                unmap_stage2_range(kvm, gpa, size);
                spin_unlock(&kvm->mmu_lock);
        }
}

int kvm_arch_prepare_memory_region(struct kvm *kvm,
                                   struct kvm_memory_slot *memslot,
                                   struct kvm_userspace_memory_region *mem,
                                   enum kvm_mr_change change)
{
        return 0;
}

void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *free,
                           struct kvm_memory_slot *dont)
{
}

int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
                            unsigned long npages)
{
        return 0;
}

void kvm_arch_memslots_updated(struct kvm *kvm)
{
}

void kvm_arch_flush_shadow_all(struct kvm *kvm)
{
}

void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
                                   struct kvm_memory_slot *slot)
{
}