Merge branches 'for-next/kvm-build-fix', 'for-next/va-refactor', 'for-next/lto',...

[platform/kernel/linux-rpi.git] / arch / arm64 / kvm / mmu.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2012 - Virtual Open Systems and Columbia University
 * Author: Christoffer Dall <c.dall@virtualopensystems.com>
 */

#include <linux/mman.h>
#include <linux/kvm_host.h>
#include <linux/io.h>
#include <linux/hugetlb.h>
#include <linux/sched/signal.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_pgtable.h>
#include <asm/kvm_ras.h>
#include <asm/kvm_asm.h>
#include <asm/kvm_emulate.h>
#include <asm/virt.h>

#include "trace.h"

static struct kvm_pgtable *hyp_pgtable;
static DEFINE_MUTEX(kvm_hyp_pgd_mutex);

static unsigned long hyp_idmap_start;
static unsigned long hyp_idmap_end;
static phys_addr_t hyp_idmap_vector;

static unsigned long io_map_base;


/*
 * Release kvm_mmu_lock periodically if the memory region is large. Otherwise,
 * we may see kernel panics with CONFIG_DETECT_HUNG_TASK,
 * CONFIG_LOCKUP_DETECTOR, CONFIG_LOCKDEP. Additionally, holding the lock too
 * long will also starve other vCPUs. We have to also make sure that the page
 * tables are not freed while we released the lock.
 */
static int stage2_apply_range(struct kvm *kvm, phys_addr_t addr,
                              phys_addr_t end,
                              int (*fn)(struct kvm_pgtable *, u64, u64),
                              bool resched)
{
        int ret;
        u64 next;

        do {
                struct kvm_pgtable *pgt = kvm->arch.mmu.pgt;
                if (!pgt)
                        return -EINVAL;

                next = stage2_pgd_addr_end(kvm, addr, end);
                ret = fn(pgt, addr, next - addr);
                if (ret)
                        break;

                if (resched && next != end)
                        cond_resched_lock(&kvm->mmu_lock);
        } while (addr = next, addr != end);

        return ret;
}

#define stage2_apply_range_resched(kvm, addr, end, fn)                  \
        stage2_apply_range(kvm, addr, end, fn, true)

static bool memslot_is_logging(struct kvm_memory_slot *memslot)
{
        return memslot->dirty_bitmap && !(memslot->flags & KVM_MEM_READONLY);
}

/**
 * kvm_flush_remote_tlbs() - flush all VM TLB entries for v7/8
 * @kvm:        pointer to kvm structure.
 *
 * Interface to HYP function to flush all VM TLB entries
 */
void kvm_flush_remote_tlbs(struct kvm *kvm)
{
        kvm_call_hyp(__kvm_tlb_flush_vmid, &kvm->arch.mmu);
}

static bool kvm_is_device_pfn(unsigned long pfn)
{
        return !pfn_valid(pfn);
}

/*
 * Unmapping vs dcache management:
 *
 * If a guest maps certain memory pages as uncached, all writes will
 * bypass the data cache and go directly to RAM.  However, the CPUs
 * can still speculate reads (not writes) and fill cache lines with
 * data.
 *
 * Those cache lines will be *clean* cache lines though, so a
 * clean+invalidate operation is equivalent to an invalidate
 * operation, because no cache lines are marked dirty.
 *
 * Those clean cache lines could be filled prior to an uncached write
 * by the guest, and the cache coherent IO subsystem would therefore
 * end up writing old data to disk.
 *
 * This is why right after unmapping a page/section and invalidating
 * the corresponding TLBs, we flush to make sure the IO subsystem will
 * never hit in the cache.
 *
 * This is all avoided on systems that have ARM64_HAS_STAGE2_FWB, as
 * we then fully enforce cacheability of RAM, no matter what the guest
 * does.
 */
/**
 * unmap_stage2_range -- Clear stage2 page table entries to unmap a range
 * @mmu:   The KVM stage-2 MMU pointer
 * @start: The intermediate physical base address of the range to unmap
 * @size:  The size of the area to unmap
 * @may_block: Whether or not we are permitted to block
 *
 * 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_s2_mmu *mmu, phys_addr_t start, u64 size,
                                 bool may_block)
{
        struct kvm *kvm = mmu->kvm;
        phys_addr_t end = start + size;

        assert_spin_locked(&kvm->mmu_lock);
        WARN_ON(size & ~PAGE_MASK);
        WARN_ON(stage2_apply_range(kvm, start, end, kvm_pgtable_stage2_unmap,
                                   may_block));
}

static void unmap_stage2_range(struct kvm_s2_mmu *mmu, phys_addr_t start, u64 size)
{
        __unmap_stage2_range(mmu, start, size, true);
}

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;

        stage2_apply_range_resched(kvm, addr, end, kvm_pgtable_stage2_flush);
}

/**
 * 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.
 */
static 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_hyp_pgds - free Hyp-mode page tables
 */
void free_hyp_pgds(void)
{
        mutex_lock(&kvm_hyp_pgd_mutex);
        if (hyp_pgtable) {
                kvm_pgtable_hyp_destroy(hyp_pgtable);
                kfree(hyp_pgtable);
        }
        mutex_unlock(&kvm_hyp_pgd_mutex);
}

static int __create_hyp_mappings(unsigned long start, unsigned long size,
                                 unsigned long phys, enum kvm_pgtable_prot prot)
{
        int err;

        mutex_lock(&kvm_hyp_pgd_mutex);
        err = kvm_pgtable_hyp_map(hyp_pgtable, start, size, phys, prot);
        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)
 * @prot:       The protection to be applied to this range
 *
 * 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, enum kvm_pgtable_prot prot)
{
        phys_addr_t phys_addr;
        unsigned long virt_addr;
        unsigned long start = kern_hyp_va((unsigned long)from);
        unsigned long end = kern_hyp_va((unsigned long)to);

        if (is_kernel_in_hyp_mode())
                return 0;

        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(virt_addr, PAGE_SIZE, phys_addr,
                                            prot);
                if (err)
                        return err;
        }

        return 0;
}

static int __create_hyp_private_mapping(phys_addr_t phys_addr, size_t size,
                                        unsigned long *haddr,
                                        enum kvm_pgtable_prot prot)
{
        unsigned long base;
        int ret = 0;

        mutex_lock(&kvm_hyp_pgd_mutex);

        /*
         * This assumes that we have enough space below the idmap
         * page to allocate our VAs. If not, the check below will
         * kick. A potential alternative would be to detect that
         * overflow and switch to an allocation above the idmap.
         *
         * The allocated size is always a multiple of PAGE_SIZE.
         */
        size = PAGE_ALIGN(size + offset_in_page(phys_addr));
        base = io_map_base - size;

        /*
         * Verify that BIT(VA_BITS - 1) hasn't been flipped by
         * allocating the new area, as it would indicate we've
         * overflowed the idmap/IO address range.
         */
        if ((base ^ io_map_base) & BIT(VA_BITS - 1))
                ret = -ENOMEM;
        else
                io_map_base = base;

        mutex_unlock(&kvm_hyp_pgd_mutex);

        if (ret)
                goto out;

        ret = __create_hyp_mappings(base, size, phys_addr, prot);
        if (ret)
                goto out;

        *haddr = base + offset_in_page(phys_addr);
out:
        return ret;
}

/**
 * create_hyp_io_mappings - Map IO into both kernel and HYP
 * @phys_addr:  The physical start address which gets mapped
 * @size:       Size of the region being mapped
 * @kaddr:      Kernel VA for this mapping
 * @haddr:      HYP VA for this mapping
 */
int create_hyp_io_mappings(phys_addr_t phys_addr, size_t size,
                           void __iomem **kaddr,
                           void __iomem **haddr)
{
        unsigned long addr;
        int ret;

        *kaddr = ioremap(phys_addr, size);
        if (!*kaddr)
                return -ENOMEM;

        if (is_kernel_in_hyp_mode()) {
                *haddr = *kaddr;
                return 0;
        }

        ret = __create_hyp_private_mapping(phys_addr, size,
                                           &addr, PAGE_HYP_DEVICE);
        if (ret) {
                iounmap(*kaddr);
                *kaddr = NULL;
                *haddr = NULL;
                return ret;
        }

        *haddr = (void __iomem *)addr;
        return 0;
}

/**
 * create_hyp_exec_mappings - Map an executable range into HYP
 * @phys_addr:  The physical start address which gets mapped
 * @size:       Size of the region being mapped
 * @haddr:      HYP VA for this mapping
 */
int create_hyp_exec_mappings(phys_addr_t phys_addr, size_t size,
                             void **haddr)
{
        unsigned long addr;
        int ret;

        BUG_ON(is_kernel_in_hyp_mode());

        ret = __create_hyp_private_mapping(phys_addr, size,
                                           &addr, PAGE_HYP_EXEC);
        if (ret) {
                *haddr = NULL;
                return ret;
        }

        *haddr = (void *)addr;
        return 0;
}

/**
 * kvm_init_stage2_mmu - Initialise a S2 MMU strucrure
 * @kvm:        The pointer to the KVM structure
 * @mmu:        The pointer to the s2 MMU structure
 *
 * Allocates only the stage-2 HW PGD level table(s).
 * 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_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu)
{
        int cpu, err;
        struct kvm_pgtable *pgt;

        if (mmu->pgt != NULL) {
                kvm_err("kvm_arch already initialized?\n");
                return -EINVAL;
        }

        pgt = kzalloc(sizeof(*pgt), GFP_KERNEL);
        if (!pgt)
                return -ENOMEM;

        err = kvm_pgtable_stage2_init(pgt, kvm);
        if (err)
                goto out_free_pgtable;

        mmu->last_vcpu_ran = alloc_percpu(typeof(*mmu->last_vcpu_ran));
        if (!mmu->last_vcpu_ran) {
                err = -ENOMEM;
                goto out_destroy_pgtable;
        }

        for_each_possible_cpu(cpu)
                *per_cpu_ptr(mmu->last_vcpu_ran, cpu) = -1;

        mmu->kvm = kvm;
        mmu->pgt = pgt;
        mmu->pgd_phys = __pa(pgt->pgd);
        mmu->vmid.vmid_gen = 0;
        return 0;

out_destroy_pgtable:
        kvm_pgtable_stage2_destroy(pgt);
out_free_pgtable:
        kfree(pgt);
        return err;
}

static void stage2_unmap_memslot(struct kvm *kvm,
                                 struct kvm_memory_slot *memslot)
{
        hva_t hva = memslot->userspace_addr;
        phys_addr_t addr = memslot->base_gfn << PAGE_SHIFT;
        phys_addr_t size = PAGE_SIZE * memslot->npages;
        hva_t reg_end = hva + size;

        /*
         * A memory region could potentially cover multiple VMAs, and any holes
         * between them, so iterate over all of them to find out if we should
         * unmap any of them.
         *
         *     +--------------------------------------------+
         * +---------------+----------------+   +----------------+
         * |   : VMA 1     |      VMA 2     |   |    VMA 3  :    |
         * +---------------+----------------+   +----------------+
         *     |               memory region                |
         *     +--------------------------------------------+
         */
        do {
                struct vm_area_struct *vma = find_vma(current->mm, hva);
                hva_t vm_start, vm_end;

                if (!vma || vma->vm_start >= reg_end)
                        break;

                /*
                 * Take the intersection of this VMA with the memory region
                 */
                vm_start = max(hva, vma->vm_start);
                vm_end = min(reg_end, vma->vm_end);

                if (!(vma->vm_flags & VM_PFNMAP)) {
                        gpa_t gpa = addr + (vm_start - memslot->userspace_addr);
                        unmap_stage2_range(&kvm->arch.mmu, gpa, vm_end - vm_start);
                }
                hva = vm_end;
        } while (hva < reg_end);
}

/**
 * stage2_unmap_vm - Unmap Stage-2 RAM mappings
 * @kvm: The struct kvm pointer
 *
 * Go through the memregions and unmap any regular RAM
 * backing memory already mapped to the VM.
 */
void stage2_unmap_vm(struct kvm *kvm)
{
        struct kvm_memslots *slots;
        struct kvm_memory_slot *memslot;
        int idx;

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

        slots = kvm_memslots(kvm);
        kvm_for_each_memslot(memslot, slots)
                stage2_unmap_memslot(kvm, memslot);

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

void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu)
{
        struct kvm *kvm = mmu->kvm;
        struct kvm_pgtable *pgt = NULL;

        spin_lock(&kvm->mmu_lock);
        pgt = mmu->pgt;
        if (pgt) {
                mmu->pgd_phys = 0;
                mmu->pgt = NULL;
                free_percpu(mmu->last_vcpu_ran);
        }
        spin_unlock(&kvm->mmu_lock);

        if (pgt) {
                kvm_pgtable_stage2_destroy(pgt);
                kfree(pgt);
        }
}

/**
 * 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
 * @writable:   Whether or not to create a writable mapping
 */
int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
                          phys_addr_t pa, unsigned long size, bool writable)
{
        phys_addr_t addr;
        int ret = 0;
        struct kvm_mmu_memory_cache cache = { 0, __GFP_ZERO, NULL, };
        struct kvm_pgtable *pgt = kvm->arch.mmu.pgt;
        enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_DEVICE |
                                     KVM_PGTABLE_PROT_R |
                                     (writable ? KVM_PGTABLE_PROT_W : 0);

        size += offset_in_page(guest_ipa);
        guest_ipa &= PAGE_MASK;

        for (addr = guest_ipa; addr < guest_ipa + size; addr += PAGE_SIZE) {
                ret = kvm_mmu_topup_memory_cache(&cache,
                                                 kvm_mmu_cache_min_pages(kvm));
                if (ret)
                        break;

                spin_lock(&kvm->mmu_lock);
                ret = kvm_pgtable_stage2_map(pgt, addr, PAGE_SIZE, pa, prot,
                                             &cache);
                spin_unlock(&kvm->mmu_lock);
                if (ret)
                        break;

                pa += PAGE_SIZE;
        }

        kvm_mmu_free_memory_cache(&cache);
        return ret;
}

/**
 * stage2_wp_range() - write protect stage2 memory region range
 * @mmu:        The KVM stage-2 MMU pointer
 * @addr:       Start address of range
 * @end:        End address of range
 */
static void stage2_wp_range(struct kvm_s2_mmu *mmu, phys_addr_t addr, phys_addr_t end)
{
        struct kvm *kvm = mmu->kvm;
        stage2_apply_range_resched(kvm, addr, end, kvm_pgtable_stage2_wrprotect);
}

/**
 * kvm_mmu_wp_memory_region() - write protect stage 2 entries for memory slot
 * @kvm:        The KVM pointer
 * @slot:       The memory slot to write protect
 *
 * Called to start logging dirty pages after memory region
 * KVM_MEM_LOG_DIRTY_PAGES operation is called. After this function returns
 * all present PUD, PMD and PTEs are write protected in the memory region.
 * Afterwards read of dirty page log can be called.
 *
 * Acquires kvm_mmu_lock. Called with kvm->slots_lock mutex acquired,
 * serializing operations for VM memory regions.
 */
void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot)
{
        struct kvm_memslots *slots = kvm_memslots(kvm);
        struct kvm_memory_slot *memslot = id_to_memslot(slots, slot);
        phys_addr_t start, end;

        if (WARN_ON_ONCE(!memslot))
                return;

        start = memslot->base_gfn << PAGE_SHIFT;
        end = (memslot->base_gfn + memslot->npages) << PAGE_SHIFT;

        spin_lock(&kvm->mmu_lock);
        stage2_wp_range(&kvm->arch.mmu, start, end);
        spin_unlock(&kvm->mmu_lock);
        kvm_flush_remote_tlbs(kvm);
}

/**
 * kvm_mmu_write_protect_pt_masked() - write protect dirty pages
 * @kvm:        The KVM pointer
 * @slot:       The memory slot associated with mask
 * @gfn_offset: The gfn offset in memory slot
 * @mask:       The mask of dirty pages at offset 'gfn_offset' in this memory
 *              slot to be write protected
 *
 * Walks bits set in mask write protects the associated pte's. Caller must
 * acquire kvm_mmu_lock.
 */
static void kvm_mmu_write_protect_pt_masked(struct kvm *kvm,
                struct kvm_memory_slot *slot,
                gfn_t gfn_offset, unsigned long mask)
{
        phys_addr_t base_gfn = slot->base_gfn + gfn_offset;
        phys_addr_t start = (base_gfn +  __ffs(mask)) << PAGE_SHIFT;
        phys_addr_t end = (base_gfn + __fls(mask) + 1) << PAGE_SHIFT;

        stage2_wp_range(&kvm->arch.mmu, start, end);
}

/*
 * kvm_arch_mmu_enable_log_dirty_pt_masked - enable dirty logging for selected
 * dirty pages.
 *
 * It calls kvm_mmu_write_protect_pt_masked to write protect selected pages to
 * enable dirty logging for them.
 */
void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm,
                struct kvm_memory_slot *slot,
                gfn_t gfn_offset, unsigned long mask)
{
        kvm_mmu_write_protect_pt_masked(kvm, slot, gfn_offset, mask);
}

static void clean_dcache_guest_page(kvm_pfn_t pfn, unsigned long size)
{
        __clean_dcache_guest_page(pfn, size);
}

static void invalidate_icache_guest_page(kvm_pfn_t pfn, unsigned long size)
{
        __invalidate_icache_guest_page(pfn, size);
}

static void kvm_send_hwpoison_signal(unsigned long address, short lsb)
{
        send_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb, current);
}

static bool fault_supports_stage2_huge_mapping(struct kvm_memory_slot *memslot,
                                               unsigned long hva,
                                               unsigned long map_size)
{
        gpa_t gpa_start;
        hva_t uaddr_start, uaddr_end;
        size_t size;

        /* The memslot and the VMA are guaranteed to be aligned to PAGE_SIZE */
        if (map_size == PAGE_SIZE)
                return true;

        size = memslot->npages * PAGE_SIZE;

        gpa_start = memslot->base_gfn << PAGE_SHIFT;

        uaddr_start = memslot->userspace_addr;
        uaddr_end = uaddr_start + size;

        /*
         * Pages belonging to memslots that don't have the same alignment
         * within a PMD/PUD for userspace and IPA cannot be mapped with stage-2
         * PMD/PUD entries, because we'll end up mapping the wrong pages.
         *
         * Consider a layout like the following:
         *
         *    memslot->userspace_addr:
         *    +-----+--------------------+--------------------+---+
         *    |abcde|fgh  Stage-1 block  |    Stage-1 block tv|xyz|
         *    +-----+--------------------+--------------------+---+
         *
         *    memslot->base_gfn << PAGE_SHIFT:
         *      +---+--------------------+--------------------+-----+
         *      |abc|def  Stage-2 block  |    Stage-2 block   |tvxyz|
         *      +---+--------------------+--------------------+-----+
         *
         * If we create those stage-2 blocks, we'll end up with this incorrect
         * mapping:
         *   d -> f
         *   e -> g
         *   f -> h
         */
        if ((gpa_start & (map_size - 1)) != (uaddr_start & (map_size - 1)))
                return false;

        /*
         * Next, let's make sure we're not trying to map anything not covered
         * by the memslot. This means we have to prohibit block size mappings
         * for the beginning and end of a non-block aligned and non-block sized
         * memory slot (illustrated by the head and tail parts of the
         * userspace view above containing pages 'abcde' and 'xyz',
         * respectively).
         *
         * Note that it doesn't matter if we do the check using the
         * userspace_addr or the base_gfn, as both are equally aligned (per
         * the check above) and equally sized.
         */
        return (hva & ~(map_size - 1)) >= uaddr_start &&
               (hva & ~(map_size - 1)) + map_size <= uaddr_end;
}

/*
 * Check if the given hva is backed by a transparent huge page (THP) and
 * whether it can be mapped using block mapping in stage2. If so, adjust
 * the stage2 PFN and IPA accordingly. Only PMD_SIZE THPs are currently
 * supported. This will need to be updated to support other THP sizes.
 *
 * Returns the size of the mapping.
 */
static unsigned long
transparent_hugepage_adjust(struct kvm_memory_slot *memslot,
                            unsigned long hva, kvm_pfn_t *pfnp,
                            phys_addr_t *ipap)
{
        kvm_pfn_t pfn = *pfnp;

        /*
         * Make sure the adjustment is done only for THP pages. Also make
         * sure that the HVA and IPA are sufficiently aligned and that the
         * block map is contained within the memslot.
         */
        if (kvm_is_transparent_hugepage(pfn) &&
            fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE)) {
                /*
                 * 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.
                 */
                *ipap &= PMD_MASK;
                kvm_release_pfn_clean(pfn);
                pfn &= ~(PTRS_PER_PMD - 1);
                kvm_get_pfn(pfn);
                *pfnp = pfn;

                return PMD_SIZE;
        }

        /* Use page mapping if we cannot use block mapping. */
        return PAGE_SIZE;
}

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 = 0;
        bool write_fault, writable, force_pte = false;
        bool exec_fault;
        bool device = false;
        unsigned long mmu_seq;
        struct kvm *kvm = vcpu->kvm;
        struct kvm_mmu_memory_cache *memcache = &vcpu->arch.mmu_page_cache;
        struct vm_area_struct *vma;
        short vma_shift;
        gfn_t gfn;
        kvm_pfn_t pfn;
        bool logging_active = memslot_is_logging(memslot);
        unsigned long vma_pagesize;
        enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R;
        struct kvm_pgtable *pgt;

        write_fault = kvm_is_write_fault(vcpu);
        exec_fault = kvm_vcpu_trap_is_exec_fault(vcpu);
        VM_BUG_ON(write_fault && exec_fault);

        if (fault_status == FSC_PERM && !write_fault && !exec_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 */
        mmap_read_lock(current->mm);
        vma = find_vma_intersection(current->mm, hva, hva + 1);
        if (unlikely(!vma)) {
                kvm_err("Failed to find VMA for hva 0x%lx\n", hva);
                mmap_read_unlock(current->mm);
                return -EFAULT;
        }

        if (is_vm_hugetlb_page(vma))
                vma_shift = huge_page_shift(hstate_vma(vma));
        else
                vma_shift = PAGE_SHIFT;

        if (logging_active ||
            (vma->vm_flags & VM_PFNMAP)) {
                force_pte = true;
                vma_shift = PAGE_SHIFT;
        }

        switch (vma_shift) {
#ifndef __PAGETABLE_PMD_FOLDED
        case PUD_SHIFT:
                if (fault_supports_stage2_huge_mapping(memslot, hva, PUD_SIZE))
                        break;
                fallthrough;
#endif
        case CONT_PMD_SHIFT:
                vma_shift = PMD_SHIFT;
                fallthrough;
        case PMD_SHIFT:
                if (fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE))
                        break;
                fallthrough;
        case CONT_PTE_SHIFT:
                vma_shift = PAGE_SHIFT;
                force_pte = true;
                fallthrough;
        case PAGE_SHIFT:
                break;
        default:
                WARN_ONCE(1, "Unknown vma_shift %d", vma_shift);
        }

        vma_pagesize = 1UL << vma_shift;
        if (vma_pagesize == PMD_SIZE || vma_pagesize == PUD_SIZE)
                fault_ipa &= ~(vma_pagesize - 1);

        gfn = fault_ipa >> PAGE_SHIFT;
        mmap_read_unlock(current->mm);

        /*
         * Permission faults just need to update the existing leaf entry,
         * and so normally don't require allocations from the memcache. The
         * only exception to this is when dirty logging is enabled at runtime
         * and a write fault needs to collapse a block entry into a table.
         */
        if (fault_status != FSC_PERM || (logging_active && write_fault)) {
                ret = kvm_mmu_topup_memory_cache(memcache,
                                                 kvm_mmu_cache_min_pages(kvm));
                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 (pfn == KVM_PFN_ERR_HWPOISON) {
                kvm_send_hwpoison_signal(hva, vma_shift);
                return 0;
        }
        if (is_error_noslot_pfn(pfn))
                return -EFAULT;

        if (kvm_is_device_pfn(pfn)) {
                device = true;
                force_pte = true;
        } else if (logging_active && !write_fault) {
                /*
                 * Only actually map the page as writable if this was a write
                 * fault.
                 */
                writable = false;
        }

        if (exec_fault && device)
                return -ENOEXEC;

        spin_lock(&kvm->mmu_lock);
        pgt = vcpu->arch.hw_mmu->pgt;
        if (mmu_notifier_retry(kvm, mmu_seq))
                goto out_unlock;

        /*
         * If we are not forced to use page mapping, check if we are
         * backed by a THP and thus use block mapping if possible.
         */
        if (vma_pagesize == PAGE_SIZE && !force_pte)
                vma_pagesize = transparent_hugepage_adjust(memslot, hva,
                                                           &pfn, &fault_ipa);
        if (writable) {
                prot |= KVM_PGTABLE_PROT_W;
                kvm_set_pfn_dirty(pfn);
                mark_page_dirty(kvm, gfn);
        }

        if (fault_status != FSC_PERM && !device)
                clean_dcache_guest_page(pfn, vma_pagesize);

        if (exec_fault) {
                prot |= KVM_PGTABLE_PROT_X;
                invalidate_icache_guest_page(pfn, vma_pagesize);
        }

        if (device)
                prot |= KVM_PGTABLE_PROT_DEVICE;
        else if (cpus_have_const_cap(ARM64_HAS_CACHE_DIC))
                prot |= KVM_PGTABLE_PROT_X;

        if (fault_status == FSC_PERM && !(logging_active && writable)) {
                ret = kvm_pgtable_stage2_relax_perms(pgt, fault_ipa, prot);
        } else {
                ret = kvm_pgtable_stage2_map(pgt, fault_ipa, vma_pagesize,
                                             __pfn_to_phys(pfn), prot,
                                             memcache);
        }

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

/* Resolve the access fault by making the page young again. */
static void handle_access_fault(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa)
{
        pte_t pte;
        kvm_pte_t kpte;
        struct kvm_s2_mmu *mmu;

        trace_kvm_access_fault(fault_ipa);

        spin_lock(&vcpu->kvm->mmu_lock);
        mmu = vcpu->arch.hw_mmu;
        kpte = kvm_pgtable_stage2_mkyoung(mmu->pgt, fault_ipa);
        spin_unlock(&vcpu->kvm->mmu_lock);

        pte = __pte(kpte);
        if (pte_valid(pte))
                kvm_set_pfn_accessed(pte_pfn(pte));
}

/**
 * kvm_handle_guest_abort - handles all 2nd stage aborts
 * @vcpu:       the VCPU pointer
 *
 * 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)
{
        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;

        fault_status = kvm_vcpu_trap_get_fault_type(vcpu);

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

        /* Synchronous External Abort? */
        if (kvm_vcpu_abt_issea(vcpu)) {
                /*
                 * For RAS the host kernel may handle this abort.
                 * There is no need to pass the error into the guest.
                 */
                if (kvm_handle_guest_sea(fault_ipa, kvm_vcpu_get_esr(vcpu)))
                        kvm_inject_vabt(vcpu);

                return 1;
        }

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

        /* Check the stage-2 fault is trans. fault or write fault */
        if (fault_status != FSC_FAULT && fault_status != FSC_PERM &&
            fault_status != FSC_ACCESS) {
                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_esr(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)) {
                /*
                 * The guest has put either its instructions or its page-tables
                 * somewhere it shouldn't have. Userspace won't be able to do
                 * anything about this (there's no syndrome for a start), so
                 * re-inject the abort back into the guest.
                 */
                if (is_iabt) {
                        ret = -ENOEXEC;
                        goto out;
                }

                if (kvm_vcpu_abt_iss1tw(vcpu)) {
                        kvm_inject_dabt(vcpu, kvm_vcpu_get_hfar(vcpu));
                        ret = 1;
                        goto out_unlock;
                }

                /*
                 * Check for a cache maintenance operation. Since we
                 * ended-up here, we know it is outside of any memory
                 * slot. But we can't find out if that is for a device,
                 * or if the guest is just being stupid. The only thing
                 * we know for sure is that this range cannot be cached.
                 *
                 * So let's assume that the guest is just being
                 * cautious, and skip the instruction.
                 */
                if (kvm_is_error_hva(hva) && kvm_vcpu_dabt_is_cm(vcpu)) {
                        kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(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, fault_ipa);
                goto out_unlock;
        }

        /* Userspace should not be able to register out-of-bounds IPAs */
        VM_BUG_ON(fault_ipa >= kvm_phys_size(vcpu->kvm));

        if (fault_status == FSC_ACCESS) {
                handle_access_fault(vcpu, fault_ipa);
                ret = 1;
                goto out_unlock;
        }

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

static int handle_hva_to_gpa(struct kvm *kvm,
                             unsigned long start,
                             unsigned long end,
                             int (*handler)(struct kvm *kvm,
                                            gpa_t gpa, u64 size,
                                            void *data),
                             void *data)
{
        struct kvm_memslots *slots;
        struct kvm_memory_slot *memslot;
        int ret = 0;

        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 gpa;

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

                gpa = hva_to_gfn_memslot(hva_start, memslot) << PAGE_SHIFT;
                ret |= handler(kvm, gpa, (u64)(hva_end - hva_start), data);
        }

        return ret;
}

static int kvm_unmap_hva_handler(struct kvm *kvm, gpa_t gpa, u64 size, void *data)
{
        unsigned flags = *(unsigned *)data;
        bool may_block = flags & MMU_NOTIFIER_RANGE_BLOCKABLE;

        __unmap_stage2_range(&kvm->arch.mmu, gpa, size, may_block);
        return 0;
}

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

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

static int kvm_set_spte_handler(struct kvm *kvm, gpa_t gpa, u64 size, void *data)
{
        kvm_pfn_t *pfn = (kvm_pfn_t *)data;

        WARN_ON(size != PAGE_SIZE);

        /*
         * The MMU notifiers will have unmapped a huge PMD before calling
         * ->change_pte() (which in turn calls kvm_set_spte_hva()) and
         * therefore we never need to clear out a huge PMD through this
         * calling path and a memcache is not required.
         */
        kvm_pgtable_stage2_map(kvm->arch.mmu.pgt, gpa, PAGE_SIZE,
                               __pfn_to_phys(*pfn), KVM_PGTABLE_PROT_R, NULL);
        return 0;
}

int kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte)
{
        unsigned long end = hva + PAGE_SIZE;
        kvm_pfn_t pfn = pte_pfn(pte);

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

        trace_kvm_set_spte_hva(hva);

        /*
         * We've moved a page around, probably through CoW, so let's treat it
         * just like a translation fault and clean the cache to the PoC.
         */
        clean_dcache_guest_page(pfn, PAGE_SIZE);
        handle_hva_to_gpa(kvm, hva, end, &kvm_set_spte_handler, &pfn);
        return 0;
}

static int kvm_age_hva_handler(struct kvm *kvm, gpa_t gpa, u64 size, void *data)
{
        pte_t pte;
        kvm_pte_t kpte;

        WARN_ON(size != PAGE_SIZE && size != PMD_SIZE && size != PUD_SIZE);
        kpte = kvm_pgtable_stage2_mkold(kvm->arch.mmu.pgt, gpa);
        pte = __pte(kpte);
        return pte_valid(pte) && pte_young(pte);
}

static int kvm_test_age_hva_handler(struct kvm *kvm, gpa_t gpa, u64 size, void *data)
{
        WARN_ON(size != PAGE_SIZE && size != PMD_SIZE && size != PUD_SIZE);
        return kvm_pgtable_stage2_is_young(kvm->arch.mmu.pgt, gpa);
}

int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end)
{
        if (!kvm->arch.mmu.pgt)
                return 0;
        trace_kvm_age_hva(start, end);
        return handle_hva_to_gpa(kvm, start, end, kvm_age_hva_handler, NULL);
}

int kvm_test_age_hva(struct kvm *kvm, unsigned long hva)
{
        if (!kvm->arch.mmu.pgt)
                return 0;
        trace_kvm_test_age_hva(hva);
        return handle_hva_to_gpa(kvm, hva, hva + PAGE_SIZE,
                                 kvm_test_age_hva_handler, NULL);
}

phys_addr_t kvm_mmu_get_httbr(void)
{
        return __pa(hyp_pgtable->pgd);
}

phys_addr_t kvm_get_idmap_vector(void)
{
        return hyp_idmap_vector;
}

static int kvm_map_idmap_text(void)
{
        unsigned long size = hyp_idmap_end - hyp_idmap_start;
        int err = __create_hyp_mappings(hyp_idmap_start, size, hyp_idmap_start,
                                        PAGE_HYP_EXEC);
        if (err)
                kvm_err("Failed to idmap %lx-%lx\n",
                        hyp_idmap_start, hyp_idmap_end);

        return err;
}

int kvm_mmu_init(void)
{
        int err;
        u32 hyp_va_bits;

        hyp_idmap_start = __pa_symbol(__hyp_idmap_text_start);
        hyp_idmap_start = ALIGN_DOWN(hyp_idmap_start, PAGE_SIZE);
        hyp_idmap_end = __pa_symbol(__hyp_idmap_text_end);
        hyp_idmap_end = ALIGN(hyp_idmap_end, PAGE_SIZE);
        hyp_idmap_vector = __pa_symbol(__kvm_hyp_init);

        /*
         * We rely on the linker script to ensure at build time that the HYP
         * init code does not cross a page boundary.
         */
        BUG_ON((hyp_idmap_start ^ (hyp_idmap_end - 1)) & PAGE_MASK);

        hyp_va_bits = 64 - ((idmap_t0sz & TCR_T0SZ_MASK) >> TCR_T0SZ_OFFSET);
        kvm_debug("Using %u-bit virtual addresses at EL2\n", hyp_va_bits);
        kvm_debug("IDMAP page: %lx\n", hyp_idmap_start);
        kvm_debug("HYP VA range: %lx:%lx\n",
                  kern_hyp_va(PAGE_OFFSET),
                  kern_hyp_va((unsigned long)high_memory - 1));

        if (hyp_idmap_start >= kern_hyp_va(PAGE_OFFSET) &&
            hyp_idmap_start <  kern_hyp_va((unsigned long)high_memory - 1) &&
            hyp_idmap_start != (unsigned long)__hyp_idmap_text_start) {
                /*
                 * The idmap page is intersecting with the VA space,
                 * it is not safe to continue further.
                 */
                kvm_err("IDMAP intersecting with HYP VA, unable to continue\n");
                err = -EINVAL;
                goto out;
        }

        hyp_pgtable = kzalloc(sizeof(*hyp_pgtable), GFP_KERNEL);
        if (!hyp_pgtable) {
                kvm_err("Hyp mode page-table not allocated\n");
                err = -ENOMEM;
                goto out;
        }

        err = kvm_pgtable_hyp_init(hyp_pgtable, hyp_va_bits);
        if (err)
                goto out_free_pgtable;

        err = kvm_map_idmap_text();
        if (err)
                goto out_destroy_pgtable;

        io_map_base = hyp_idmap_start;
        return 0;

out_destroy_pgtable:
        kvm_pgtable_hyp_destroy(hyp_pgtable);
out_free_pgtable:
        kfree(hyp_pgtable);
        hyp_pgtable = NULL;
out:
        return err;
}

void kvm_arch_commit_memory_region(struct kvm *kvm,
                                   const struct kvm_userspace_memory_region *mem,
                                   struct kvm_memory_slot *old,
                                   const struct kvm_memory_slot *new,
                                   enum kvm_mr_change change)
{
        /*
         * At this point memslot has been committed and there is an
         * allocated dirty_bitmap[], dirty pages will be tracked while the
         * memory slot is write protected.
         */
        if (change != KVM_MR_DELETE && mem->flags & KVM_MEM_LOG_DIRTY_PAGES) {
                /*
                 * If we're with initial-all-set, we don't need to write
                 * protect any pages because they're all reported as dirty.
                 * Huge pages and normal pages will be write protect gradually.
                 */
                if (!kvm_dirty_log_manual_protect_and_init_set(kvm)) {
                        kvm_mmu_wp_memory_region(kvm, mem->slot);
                }
        }
}

int kvm_arch_prepare_memory_region(struct kvm *kvm,
                                   struct kvm_memory_slot *memslot,
                                   const struct kvm_userspace_memory_region *mem,
                                   enum kvm_mr_change change)
{
        hva_t hva = mem->userspace_addr;
        hva_t reg_end = hva + mem->memory_size;
        bool writable = !(mem->flags & KVM_MEM_READONLY);
        int ret = 0;

        if (change != KVM_MR_CREATE && change != KVM_MR_MOVE &&
                        change != KVM_MR_FLAGS_ONLY)
                return 0;

        /*
         * Prevent userspace from creating a memory region outside of the IPA
         * space addressable by the KVM guest IPA space.
         */
        if (memslot->base_gfn + memslot->npages >=
            (kvm_phys_size(kvm) >> PAGE_SHIFT))
                return -EFAULT;

        mmap_read_lock(current->mm);
        /*
         * A memory region could potentially cover multiple VMAs, and any holes
         * between them, so iterate over all of them to find out if we can map
         * any of them right now.
         *
         *     +--------------------------------------------+
         * +---------------+----------------+   +----------------+
         * |   : VMA 1     |      VMA 2     |   |    VMA 3  :    |
         * +---------------+----------------+   +----------------+
         *     |               memory region                |
         *     +--------------------------------------------+
         */
        do {
                struct vm_area_struct *vma = find_vma(current->mm, hva);
                hva_t vm_start, vm_end;

                if (!vma || vma->vm_start >= reg_end)
                        break;

                /*
                 * Take the intersection of this VMA with the memory region
                 */
                vm_start = max(hva, vma->vm_start);
                vm_end = min(reg_end, vma->vm_end);

                if (vma->vm_flags & VM_PFNMAP) {
                        gpa_t gpa = mem->guest_phys_addr +
                                    (vm_start - mem->userspace_addr);
                        phys_addr_t pa;

                        pa = (phys_addr_t)vma->vm_pgoff << PAGE_SHIFT;
                        pa += vm_start - vma->vm_start;

                        /* IO region dirty page logging not allowed */
                        if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES) {
                                ret = -EINVAL;
                                goto out;
                        }

                        ret = kvm_phys_addr_ioremap(kvm, gpa, pa,
                                                    vm_end - vm_start,
                                                    writable);
                        if (ret)
                                break;
                }
                hva = vm_end;
        } while (hva < reg_end);

        if (change == KVM_MR_FLAGS_ONLY)
                goto out;

        spin_lock(&kvm->mmu_lock);
        if (ret)
                unmap_stage2_range(&kvm->arch.mmu, mem->guest_phys_addr, mem->memory_size);
        else if (!cpus_have_final_cap(ARM64_HAS_STAGE2_FWB))
                stage2_flush_memslot(kvm, memslot);
        spin_unlock(&kvm->mmu_lock);
out:
        mmap_read_unlock(current->mm);
        return ret;
}

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

void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen)
{
}

void kvm_arch_flush_shadow_all(struct kvm *kvm)
{
        kvm_free_stage2_pgd(&kvm->arch.mmu);
}

void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
                                   struct kvm_memory_slot *slot)
{
        gpa_t gpa = slot->base_gfn << PAGE_SHIFT;
        phys_addr_t size = slot->npages << PAGE_SHIFT;

        spin_lock(&kvm->mmu_lock);
        unmap_stage2_range(&kvm->arch.mmu, gpa, size);
        spin_unlock(&kvm->mmu_lock);
}

/*
 * See note at ARMv7 ARM B1.14.4 (TL;DR: S/W ops are not easily virtualized).
 *
 * Main problems:
 * - S/W ops are local to a CPU (not broadcast)
 * - We have line migration behind our back (speculation)
 * - System caches don't support S/W at all (damn!)
 *
 * In the face of the above, the best we can do is to try and convert
 * S/W ops to VA ops. Because the guest is not allowed to infer the
 * S/W to PA mapping, it can only use S/W to nuke the whole cache,
 * which is a rather good thing for us.
 *
 * Also, it is only used when turning caches on/off ("The expected
 * usage of the cache maintenance instructions that operate by set/way
 * is associated with the cache maintenance instructions associated
 * with the powerdown and powerup of caches, if this is required by
 * the implementation.").
 *
 * We use the following policy:
 *
 * - If we trap a S/W operation, we enable VM trapping to detect
 *   caches being turned on/off, and do a full clean.
 *
 * - We flush the caches on both caches being turned on and off.
 *
 * - Once the caches are enabled, we stop trapping VM ops.
 */
void kvm_set_way_flush(struct kvm_vcpu *vcpu)
{
        unsigned long hcr = *vcpu_hcr(vcpu);

        /*
         * If this is the first time we do a S/W operation
         * (i.e. HCR_TVM not set) flush the whole memory, and set the
         * VM trapping.
         *
         * Otherwise, rely on the VM trapping to wait for the MMU +
         * Caches to be turned off. At that point, we'll be able to
         * clean the caches again.
         */
        if (!(hcr & HCR_TVM)) {
                trace_kvm_set_way_flush(*vcpu_pc(vcpu),
                                        vcpu_has_cache_enabled(vcpu));
                stage2_flush_vm(vcpu->kvm);
                *vcpu_hcr(vcpu) = hcr | HCR_TVM;
        }
}

void kvm_toggle_cache(struct kvm_vcpu *vcpu, bool was_enabled)
{
        bool now_enabled = vcpu_has_cache_enabled(vcpu);

        /*
         * If switching the MMU+caches on, need to invalidate the caches.
         * If switching it off, need to clean the caches.
         * Clean + invalidate does the trick always.
         */
        if (now_enabled != was_enabled)
                stage2_flush_vm(vcpu->kvm);

        /* Caches are now on, stop trapping VM ops (until a S/W op) */
        if (now_enabled)
                *vcpu_hcr(vcpu) &= ~HCR_TVM;

        trace_kvm_toggle_cache(*vcpu_pc(vcpu), was_enabled, now_enabled);
}