diff options
Diffstat (limited to 'arch/loongarch/kvm/mmu.c')
| -rw-r--r-- | arch/loongarch/kvm/mmu.c | 956 |
1 files changed, 956 insertions, 0 deletions
diff --git a/arch/loongarch/kvm/mmu.c b/arch/loongarch/kvm/mmu.c new file mode 100644 index 000000000000..a556cff35740 --- /dev/null +++ b/arch/loongarch/kvm/mmu.c @@ -0,0 +1,956 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2020-2023 Loongson Technology Corporation Limited + */ + +#include <linux/highmem.h> +#include <linux/hugetlb.h> +#include <linux/kvm_host.h> +#include <linux/page-flags.h> +#include <linux/uaccess.h> +#include <asm/mmu_context.h> +#include <asm/pgalloc.h> +#include <asm/tlb.h> +#include <asm/kvm_mmu.h> + +static inline bool kvm_hugepage_capable(struct kvm_memory_slot *slot) +{ + return slot->arch.flags & KVM_MEM_HUGEPAGE_CAPABLE; +} + +static inline bool kvm_hugepage_incapable(struct kvm_memory_slot *slot) +{ + return slot->arch.flags & KVM_MEM_HUGEPAGE_INCAPABLE; +} + +static inline void kvm_ptw_prepare(struct kvm *kvm, kvm_ptw_ctx *ctx) +{ + ctx->level = kvm->arch.root_level; + /* pte table */ + ctx->invalid_ptes = kvm->arch.invalid_ptes; + ctx->pte_shifts = kvm->arch.pte_shifts; + ctx->pgtable_shift = ctx->pte_shifts[ctx->level]; + ctx->invalid_entry = ctx->invalid_ptes[ctx->level]; + ctx->opaque = kvm; +} + +/* + * Mark a range of guest physical address space old (all accesses fault) in the + * VM's GPA page table to allow detection of commonly used pages. + */ +static int kvm_mkold_pte(kvm_pte_t *pte, phys_addr_t addr, kvm_ptw_ctx *ctx) +{ + if (kvm_pte_young(*pte)) { + *pte = kvm_pte_mkold(*pte); + return 1; + } + + return 0; +} + +/* + * Mark a range of guest physical address space clean (writes fault) in the VM's + * GPA page table to allow dirty page tracking. + */ +static int kvm_mkclean_pte(kvm_pte_t *pte, phys_addr_t addr, kvm_ptw_ctx *ctx) +{ + gfn_t offset; + kvm_pte_t val; + + val = *pte; + /* + * For kvm_arch_mmu_enable_log_dirty_pt_masked with mask, start and end + * may cross hugepage, for first huge page parameter addr is equal to + * start, however for the second huge page addr is base address of + * this huge page, rather than start or end address + */ + if ((ctx->flag & _KVM_HAS_PGMASK) && !kvm_pte_huge(val)) { + offset = (addr >> PAGE_SHIFT) - ctx->gfn; + if (!(BIT(offset) & ctx->mask)) + return 0; + } + + /* + * Need not split huge page now, just set write-proect pte bit + * Split huge page until next write fault + */ + if (kvm_pte_dirty(val)) { + *pte = kvm_pte_mkclean(val); + return 1; + } + + return 0; +} + +/* + * Clear pte entry + */ +static int kvm_flush_pte(kvm_pte_t *pte, phys_addr_t addr, kvm_ptw_ctx *ctx) +{ + struct kvm *kvm; + + kvm = ctx->opaque; + if (ctx->level) + kvm->stat.hugepages--; + else + kvm->stat.pages--; + + *pte = ctx->invalid_entry; + + return 1; +} + +/* + * kvm_pgd_alloc() - Allocate and initialise a KVM GPA page directory. + * + * Allocate a blank KVM GPA page directory (PGD) for representing guest physical + * to host physical page mappings. + * + * Returns: Pointer to new KVM GPA page directory. + * NULL on allocation failure. + */ +kvm_pte_t *kvm_pgd_alloc(void) +{ + kvm_pte_t *pgd; + + pgd = (kvm_pte_t *)__get_free_pages(GFP_KERNEL, 0); + if (pgd) + pgd_init((void *)pgd); + + return pgd; +} + +static void _kvm_pte_init(void *addr, unsigned long val) +{ + unsigned long *p, *end; + + p = (unsigned long *)addr; + end = p + PTRS_PER_PTE; + do { + p[0] = val; + p[1] = val; + p[2] = val; + p[3] = val; + p[4] = val; + p += 8; + p[-3] = val; + p[-2] = val; + p[-1] = val; + } while (p != end); +} + +/* + * Caller must hold kvm->mm_lock + * + * Walk the page tables of kvm to find the PTE corresponding to the + * address @addr. If page tables don't exist for @addr, they will be created + * from the MMU cache if @cache is not NULL. + */ +static kvm_pte_t *kvm_populate_gpa(struct kvm *kvm, + struct kvm_mmu_memory_cache *cache, + unsigned long addr, int level) +{ + kvm_ptw_ctx ctx; + kvm_pte_t *entry, *child; + + kvm_ptw_prepare(kvm, &ctx); + child = kvm->arch.pgd; + while (ctx.level > level) { + entry = kvm_pgtable_offset(&ctx, child, addr); + if (kvm_pte_none(&ctx, entry)) { + if (!cache) + return NULL; + + child = kvm_mmu_memory_cache_alloc(cache); + _kvm_pte_init(child, ctx.invalid_ptes[ctx.level - 1]); + kvm_set_pte(entry, __pa(child)); + } else if (kvm_pte_huge(*entry)) { + return entry; + } else + child = (kvm_pte_t *)__va(PHYSADDR(*entry)); + kvm_ptw_enter(&ctx); + } + + entry = kvm_pgtable_offset(&ctx, child, addr); + + return entry; +} + +/* + * Page walker for VM shadow mmu at last level + * The last level is small pte page or huge pmd page + */ +static int kvm_ptw_leaf(kvm_pte_t *dir, phys_addr_t addr, phys_addr_t end, kvm_ptw_ctx *ctx) +{ + int ret; + phys_addr_t next, start, size; + struct list_head *list; + kvm_pte_t *entry, *child; + + ret = 0; + start = addr; + child = (kvm_pte_t *)__va(PHYSADDR(*dir)); + entry = kvm_pgtable_offset(ctx, child, addr); + do { + next = addr + (0x1UL << ctx->pgtable_shift); + if (!kvm_pte_present(ctx, entry)) + continue; + + ret |= ctx->ops(entry, addr, ctx); + } while (entry++, addr = next, addr < end); + + if (kvm_need_flush(ctx)) { + size = 0x1UL << (ctx->pgtable_shift + PAGE_SHIFT - 3); + if (start + size == end) { + list = (struct list_head *)child; + list_add_tail(list, &ctx->list); + *dir = ctx->invalid_ptes[ctx->level + 1]; + } + } + + return ret; +} + +/* + * Page walker for VM shadow mmu at page table dir level + */ +static int kvm_ptw_dir(kvm_pte_t *dir, phys_addr_t addr, phys_addr_t end, kvm_ptw_ctx *ctx) +{ + int ret; + phys_addr_t next, start, size; + struct list_head *list; + kvm_pte_t *entry, *child; + + ret = 0; + start = addr; + child = (kvm_pte_t *)__va(PHYSADDR(*dir)); + entry = kvm_pgtable_offset(ctx, child, addr); + do { + next = kvm_pgtable_addr_end(ctx, addr, end); + if (!kvm_pte_present(ctx, entry)) + continue; + + if (kvm_pte_huge(*entry)) { + ret |= ctx->ops(entry, addr, ctx); + continue; + } + + kvm_ptw_enter(ctx); + if (ctx->level == 0) + ret |= kvm_ptw_leaf(entry, addr, next, ctx); + else + ret |= kvm_ptw_dir(entry, addr, next, ctx); + kvm_ptw_exit(ctx); + } while (entry++, addr = next, addr < end); + + if (kvm_need_flush(ctx)) { + size = 0x1UL << (ctx->pgtable_shift + PAGE_SHIFT - 3); + if (start + size == end) { + list = (struct list_head *)child; + list_add_tail(list, &ctx->list); + *dir = ctx->invalid_ptes[ctx->level + 1]; + } + } + + return ret; +} + +/* + * Page walker for VM shadow mmu at page root table + */ +static int kvm_ptw_top(kvm_pte_t *dir, phys_addr_t addr, phys_addr_t end, kvm_ptw_ctx *ctx) +{ + int ret; + phys_addr_t next; + kvm_pte_t *entry; + + ret = 0; + entry = kvm_pgtable_offset(ctx, dir, addr); + do { + next = kvm_pgtable_addr_end(ctx, addr, end); + if (!kvm_pte_present(ctx, entry)) + continue; + + kvm_ptw_enter(ctx); + ret |= kvm_ptw_dir(entry, addr, next, ctx); + kvm_ptw_exit(ctx); + } while (entry++, addr = next, addr < end); + + return ret; +} + +/* + * kvm_flush_range() - Flush a range of guest physical addresses. + * @kvm: KVM pointer. + * @start_gfn: Guest frame number of first page in GPA range to flush. + * @end_gfn: Guest frame number of last page in GPA range to flush. + * @lock: Whether to hold mmu_lock or not + * + * Flushes a range of GPA mappings from the GPA page tables. + */ +static void kvm_flush_range(struct kvm *kvm, gfn_t start_gfn, gfn_t end_gfn, int lock) +{ + int ret; + kvm_ptw_ctx ctx; + struct list_head *pos, *temp; + + ctx.ops = kvm_flush_pte; + ctx.flag = _KVM_FLUSH_PGTABLE; + kvm_ptw_prepare(kvm, &ctx); + INIT_LIST_HEAD(&ctx.list); + + if (lock) { + spin_lock(&kvm->mmu_lock); + ret = kvm_ptw_top(kvm->arch.pgd, start_gfn << PAGE_SHIFT, + end_gfn << PAGE_SHIFT, &ctx); + spin_unlock(&kvm->mmu_lock); + } else + ret = kvm_ptw_top(kvm->arch.pgd, start_gfn << PAGE_SHIFT, + end_gfn << PAGE_SHIFT, &ctx); + + /* Flush vpid for each vCPU individually */ + if (ret) + kvm_flush_remote_tlbs(kvm); + + /* + * free pte table page after mmu_lock + * the pte table page is linked together with ctx.list + */ + list_for_each_safe(pos, temp, &ctx.list) { + list_del(pos); + free_page((unsigned long)pos); + } +} + +/* + * kvm_mkclean_gpa_pt() - Make a range of guest physical addresses clean. + * @kvm: KVM pointer. + * @start_gfn: Guest frame number of first page in GPA range to flush. + * @end_gfn: Guest frame number of last page in GPA range to flush. + * + * Make a range of GPA mappings clean so that guest writes will fault and + * trigger dirty page logging. + * + * The caller must hold the @kvm->mmu_lock spinlock. + * + * Returns: Whether any GPA mappings were modified, which would require + * derived mappings (GVA page tables & TLB enties) to be + * invalidated. + */ +static int kvm_mkclean_gpa_pt(struct kvm *kvm, gfn_t start_gfn, gfn_t end_gfn) +{ + kvm_ptw_ctx ctx; + + ctx.ops = kvm_mkclean_pte; + ctx.flag = 0; + kvm_ptw_prepare(kvm, &ctx); + return kvm_ptw_top(kvm->arch.pgd, start_gfn << PAGE_SHIFT, end_gfn << PAGE_SHIFT, &ctx); +} + +/* + * kvm_arch_mmu_enable_log_dirty_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. + */ +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_ptw_ctx ctx; + gfn_t base_gfn = slot->base_gfn + gfn_offset; + gfn_t start = base_gfn + __ffs(mask); + gfn_t end = base_gfn + __fls(mask) + 1; + + ctx.ops = kvm_mkclean_pte; + ctx.flag = _KVM_HAS_PGMASK; + ctx.mask = mask; + ctx.gfn = base_gfn; + kvm_ptw_prepare(kvm, &ctx); + + kvm_ptw_top(kvm->arch.pgd, start << PAGE_SHIFT, end << PAGE_SHIFT, &ctx); +} + +int kvm_arch_prepare_memory_region(struct kvm *kvm, const struct kvm_memory_slot *old, + struct kvm_memory_slot *new, enum kvm_mr_change change) +{ + gpa_t gpa_start; + hva_t hva_start; + size_t size, gpa_offset, hva_offset; + + if ((change != KVM_MR_MOVE) && (change != KVM_MR_CREATE)) + return 0; + /* + * Prevent userspace from creating a memory region outside of the + * VM GPA address space + */ + if ((new->base_gfn + new->npages) > (kvm->arch.gpa_size >> PAGE_SHIFT)) + return -ENOMEM; + + new->arch.flags = 0; + size = new->npages * PAGE_SIZE; + gpa_start = new->base_gfn << PAGE_SHIFT; + hva_start = new->userspace_addr; + if (IS_ALIGNED(size, PMD_SIZE) && IS_ALIGNED(gpa_start, PMD_SIZE) + && IS_ALIGNED(hva_start, PMD_SIZE)) + new->arch.flags |= KVM_MEM_HUGEPAGE_CAPABLE; + else { + /* + * Pages belonging to memslots that don't have the same + * alignment within a PMD for userspace and GPA cannot be + * mapped with PMD 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_SIZE: + * +---+--------------------+--------------------+-----+ + * |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 + */ + gpa_offset = gpa_start & (PMD_SIZE - 1); + hva_offset = hva_start & (PMD_SIZE - 1); + if (gpa_offset != hva_offset) { + new->arch.flags |= KVM_MEM_HUGEPAGE_INCAPABLE; + } else { + if (gpa_offset == 0) + gpa_offset = PMD_SIZE; + if ((size + gpa_offset) < (PMD_SIZE * 2)) + new->arch.flags |= KVM_MEM_HUGEPAGE_INCAPABLE; + } + } + + return 0; +} + +void kvm_arch_commit_memory_region(struct kvm *kvm, + struct kvm_memory_slot *old, + const struct kvm_memory_slot *new, + enum kvm_mr_change change) +{ + int needs_flush; + + /* + * If dirty page logging is enabled, write protect all pages in the slot + * ready for dirty logging. + * + * There is no need to do this in any of the following cases: + * CREATE: No dirty mappings will already exist. + * MOVE/DELETE: The old mappings will already have been cleaned up by + * kvm_arch_flush_shadow_memslot() + */ + if (change == KVM_MR_FLAGS_ONLY && + (!(old->flags & KVM_MEM_LOG_DIRTY_PAGES) && + new->flags & KVM_MEM_LOG_DIRTY_PAGES)) { + spin_lock(&kvm->mmu_lock); + /* Write protect GPA page table entries */ + needs_flush = kvm_mkclean_gpa_pt(kvm, new->base_gfn, + new->base_gfn + new->npages); + spin_unlock(&kvm->mmu_lock); + if (needs_flush) + kvm_flush_remote_tlbs(kvm); + } +} + +void kvm_arch_flush_shadow_all(struct kvm *kvm) +{ + kvm_flush_range(kvm, 0, kvm->arch.gpa_size >> PAGE_SHIFT, 0); +} + +void kvm_arch_flush_shadow_memslot(struct kvm *kvm, struct kvm_memory_slot *slot) +{ + /* + * The slot has been made invalid (ready for moving or deletion), so we + * need to ensure that it can no longer be accessed by any guest vCPUs. + */ + kvm_flush_range(kvm, slot->base_gfn, slot->base_gfn + slot->npages, 1); +} + +bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range) +{ + kvm_ptw_ctx ctx; + + ctx.flag = 0; + ctx.ops = kvm_flush_pte; + kvm_ptw_prepare(kvm, &ctx); + INIT_LIST_HEAD(&ctx.list); + + return kvm_ptw_top(kvm->arch.pgd, range->start << PAGE_SHIFT, + range->end << PAGE_SHIFT, &ctx); +} + +bool kvm_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range) +{ + unsigned long prot_bits; + kvm_pte_t *ptep; + kvm_pfn_t pfn = pte_pfn(range->arg.pte); + gpa_t gpa = range->start << PAGE_SHIFT; + + ptep = kvm_populate_gpa(kvm, NULL, gpa, 0); + if (!ptep) + return false; + + /* Replacing an absent or old page doesn't need flushes */ + if (!kvm_pte_present(NULL, ptep) || !kvm_pte_young(*ptep)) { + kvm_set_pte(ptep, 0); + return false; + } + + /* Fill new pte if write protected or page migrated */ + prot_bits = _PAGE_PRESENT | __READABLE; + prot_bits |= _CACHE_MASK & pte_val(range->arg.pte); + + /* + * Set _PAGE_WRITE or _PAGE_DIRTY iff old and new pte both support + * _PAGE_WRITE for map_page_fast if next page write fault + * _PAGE_DIRTY since gpa has already recorded as dirty page + */ + prot_bits |= __WRITEABLE & *ptep & pte_val(range->arg.pte); + kvm_set_pte(ptep, kvm_pfn_pte(pfn, __pgprot(prot_bits))); + + return true; +} + +bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) +{ + kvm_ptw_ctx ctx; + + ctx.flag = 0; + ctx.ops = kvm_mkold_pte; + kvm_ptw_prepare(kvm, &ctx); + + return kvm_ptw_top(kvm->arch.pgd, range->start << PAGE_SHIFT, + range->end << PAGE_SHIFT, &ctx); +} + +bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) +{ + gpa_t gpa = range->start << PAGE_SHIFT; + kvm_pte_t *ptep = kvm_populate_gpa(kvm, NULL, gpa, 0); + + if (ptep && kvm_pte_present(NULL, ptep) && kvm_pte_young(*ptep)) + return true; + + return false; +} + +/* + * kvm_map_page_fast() - Fast path GPA fault handler. + * @vcpu: vCPU pointer. + * @gpa: Guest physical address of fault. + * @write: Whether the fault was due to a write. + * + * Perform fast path GPA fault handling, doing all that can be done without + * calling into KVM. This handles marking old pages young (for idle page + * tracking), and dirtying of clean pages (for dirty page logging). + * + * Returns: 0 on success, in which case we can update derived mappings and + * resume guest execution. + * -EFAULT on failure due to absent GPA mapping or write to + * read-only page, in which case KVM must be consulted. + */ +static int kvm_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa, bool write) +{ + int ret = 0; + kvm_pfn_t pfn = 0; + kvm_pte_t *ptep, changed, new; + gfn_t gfn = gpa >> PAGE_SHIFT; + struct kvm *kvm = vcpu->kvm; + struct kvm_memory_slot *slot; + + spin_lock(&kvm->mmu_lock); + + /* Fast path - just check GPA page table for an existing entry */ + ptep = kvm_populate_gpa(kvm, NULL, gpa, 0); + if (!ptep || !kvm_pte_present(NULL, ptep)) { + ret = -EFAULT; + goto out; + } + + /* Track access to pages marked old */ + new = *ptep; + if (!kvm_pte_young(new)) + new = kvm_pte_mkyoung(new); + /* call kvm_set_pfn_accessed() after unlock */ + + if (write && !kvm_pte_dirty(new)) { + if (!kvm_pte_write(new)) { + ret = -EFAULT; + goto out; + } + + if (kvm_pte_huge(new)) { + /* + * Do not set write permission when dirty logging is + * enabled for HugePages + */ + slot = gfn_to_memslot(kvm, gfn); + if (kvm_slot_dirty_track_enabled(slot)) { + ret = -EFAULT; + goto out; + } + } + + /* Track dirtying of writeable pages */ + new = kvm_pte_mkdirty(new); + } + + changed = new ^ (*ptep); + if (changed) { + kvm_set_pte(ptep, new); + pfn = kvm_pte_pfn(new); + } + spin_unlock(&kvm->mmu_lock); + + /* + * Fixme: pfn may be freed after mmu_lock + * kvm_try_get_pfn(pfn)/kvm_release_pfn pair to prevent this? + */ + if (kvm_pte_young(changed)) + kvm_set_pfn_accessed(pfn); + + if (kvm_pte_dirty(changed)) { + mark_page_dirty(kvm, gfn); + kvm_set_pfn_dirty(pfn); + } + return ret; +out: + spin_unlock(&kvm->mmu_lock); + return ret; +} + +static bool fault_supports_huge_mapping(struct kvm_memory_slot *memslot, + unsigned long hva, bool write) +{ + hva_t start, end; + + /* Disable dirty logging on HugePages */ + if (kvm_slot_dirty_track_enabled(memslot) && write) + return false; + + if (kvm_hugepage_capable(memslot)) + return true; + + if (kvm_hugepage_incapable(memslot)) + return false; + + start = memslot->userspace_addr; + end = start + memslot->npages * PAGE_SIZE; + + /* + * 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 >= ALIGN(start, PMD_SIZE)) && (hva < ALIGN_DOWN(end, PMD_SIZE)); +} + +/* + * Lookup the mapping level for @gfn in the current mm. + * + * WARNING! Use of host_pfn_mapping_level() requires the caller and the end + * consumer to be tied into KVM's handlers for MMU notifier events! + * + * There are several ways to safely use this helper: + * + * - Check mmu_invalidate_retry_gfn() after grabbing the mapping level, before + * consuming it. In this case, mmu_lock doesn't need to be held during the + * lookup, but it does need to be held while checking the MMU notifier. + * + * - Hold mmu_lock AND ensure there is no in-progress MMU notifier invalidation + * event for the hva. This can be done by explicit checking the MMU notifier + * or by ensuring that KVM already has a valid mapping that covers the hva. + * + * - Do not use the result to install new mappings, e.g. use the host mapping + * level only to decide whether or not to zap an entry. In this case, it's + * not required to hold mmu_lock (though it's highly likely the caller will + * want to hold mmu_lock anyways, e.g. to modify SPTEs). + * + * Note! The lookup can still race with modifications to host page tables, but + * the above "rules" ensure KVM will not _consume_ the result of the walk if a + * race with the primary MMU occurs. + */ +static int host_pfn_mapping_level(struct kvm *kvm, gfn_t gfn, + const struct kvm_memory_slot *slot) +{ + int level = 0; + unsigned long hva; + unsigned long flags; + pgd_t pgd; + p4d_t p4d; + pud_t pud; + pmd_t pmd; + + /* + * Note, using the already-retrieved memslot and __gfn_to_hva_memslot() + * is not solely for performance, it's also necessary to avoid the + * "writable" check in __gfn_to_hva_many(), which will always fail on + * read-only memslots due to gfn_to_hva() assuming writes. Earlier + * page fault steps have already verified the guest isn't writing a + * read-only memslot. + */ + hva = __gfn_to_hva_memslot(slot, gfn); + + /* + * Disable IRQs to prevent concurrent tear down of host page tables, + * e.g. if the primary MMU promotes a P*D to a huge page and then frees + * the original page table. + */ + local_irq_save(flags); + + /* + * Read each entry once. As above, a non-leaf entry can be promoted to + * a huge page _during_ this walk. Re-reading the entry could send the + * walk into the weeks, e.g. p*d_leaf() returns false (sees the old + * value) and then p*d_offset() walks into the target huge page instead + * of the old page table (sees the new value). + */ + pgd = READ_ONCE(*pgd_offset(kvm->mm, hva)); + if (pgd_none(pgd)) + goto out; + + p4d = READ_ONCE(*p4d_offset(&pgd, hva)); + if (p4d_none(p4d) || !p4d_present(p4d)) + goto out; + + pud = READ_ONCE(*pud_offset(&p4d, hva)); + if (pud_none(pud) || !pud_present(pud)) + goto out; + + pmd = READ_ONCE(*pmd_offset(&pud, hva)); + if (pmd_none(pmd) || !pmd_present(pmd)) + goto out; + + if (kvm_pte_huge(pmd_val(pmd))) + level = 1; + +out: + local_irq_restore(flags); + return level; +} + +/* + * Split huge page + */ +static kvm_pte_t *kvm_split_huge(struct kvm_vcpu *vcpu, kvm_pte_t *ptep, gfn_t gfn) +{ + int i; + kvm_pte_t val, *child; + struct kvm *kvm = vcpu->kvm; + struct kvm_mmu_memory_cache *memcache; + + memcache = &vcpu->arch.mmu_page_cache; + child = kvm_mmu_memory_cache_alloc(memcache); + val = kvm_pte_mksmall(*ptep); + for (i = 0; i < PTRS_PER_PTE; i++) { + kvm_set_pte(child + i, val); + val += PAGE_SIZE; + } + + /* The later kvm_flush_tlb_gpa() will flush hugepage tlb */ + kvm_set_pte(ptep, __pa(child)); + + kvm->stat.hugepages--; + kvm->stat.pages += PTRS_PER_PTE; + + return child + (gfn & (PTRS_PER_PTE - 1)); +} + +/* + * kvm_map_page() - Map a guest physical page. + * @vcpu: vCPU pointer. + * @gpa: Guest physical address of fault. + * @write: Whether the fault was due to a write. + * + * Handle GPA faults by creating a new GPA mapping (or updating an existing + * one). + * + * This takes care of marking pages young or dirty (idle/dirty page tracking), + * asking KVM for the corresponding PFN, and creating a mapping in the GPA page + * tables. Derived mappings (GVA page tables and TLBs) must be handled by the + * caller. + * + * Returns: 0 on success + * -EFAULT if there is no memory region at @gpa or a write was + * attempted to a read-only memory region. This is usually handled + * as an MMIO access. + */ +static int kvm_map_page(struct kvm_vcpu *vcpu, unsigned long gpa, bool write) +{ + bool writeable; + int srcu_idx, err, retry_no = 0, level; + unsigned long hva, mmu_seq, prot_bits; + kvm_pfn_t pfn; + kvm_pte_t *ptep, new_pte; + gfn_t gfn = gpa >> PAGE_SHIFT; + struct kvm *kvm = vcpu->kvm; + struct kvm_memory_slot *memslot; + struct kvm_mmu_memory_cache *memcache = &vcpu->arch.mmu_page_cache; + + /* Try the fast path to handle old / clean pages */ + srcu_idx = srcu_read_lock(&kvm->srcu); + err = kvm_map_page_fast(vcpu, gpa, write); + if (!err) + goto out; + + memslot = gfn_to_memslot(kvm, gfn); + hva = gfn_to_hva_memslot_prot(memslot, gfn, &writeable); + if (kvm_is_error_hva(hva) || (write && !writeable)) { + err = -EFAULT; + goto out; + } + + /* We need a minimum of cached pages ready for page table creation */ + err = kvm_mmu_topup_memory_cache(memcache, KVM_MMU_CACHE_MIN_PAGES); + if (err) + goto out; + +retry: + /* + * Used to check for invalidations in progress, of the pfn that is + * returned by pfn_to_pfn_prot below. + */ + mmu_seq = kvm->mmu_invalidate_seq; + /* + * Ensure the read of mmu_invalidate_seq isn't reordered with PTE reads in + * gfn_to_pfn_prot() (which calls get_user_pages()), so that we don't + * risk the page we get a reference to getting unmapped before we have a + * chance to grab the mmu_lock without mmu_invalidate_retry() noticing. + * + * This smp_rmb() pairs with the effective smp_wmb() of the combination + * of the pte_unmap_unlock() after the PTE is zapped, and the + * spin_lock() in kvm_mmu_invalidate_invalidate_<page|range_end>() before + * mmu_invalidate_seq is incremented. + */ + smp_rmb(); + + /* Slow path - ask KVM core whether we can access this GPA */ + pfn = gfn_to_pfn_prot(kvm, gfn, write, &writeable); + if (is_error_noslot_pfn(pfn)) { + err = -EFAULT; + goto out; + } + + /* Check if an invalidation has taken place since we got pfn */ + spin_lock(&kvm->mmu_lock); + if (mmu_invalidate_retry_gfn(kvm, mmu_seq, gfn)) { + /* + * This can happen when mappings are changed asynchronously, but + * also synchronously if a COW is triggered by + * gfn_to_pfn_prot(). + */ + spin_unlock(&kvm->mmu_lock); + kvm_release_pfn_clean(pfn); + if (retry_no > 100) { + retry_no = 0; + schedule(); + } + retry_no++; + goto retry; + } + + /* + * For emulated devices such virtio device, actual cache attribute is + * determined by physical machine. + * For pass through physical device, it should be uncachable + */ + prot_bits = _PAGE_PRESENT | __READABLE; + if (pfn_valid(pfn)) + prot_bits |= _CACHE_CC; + else + prot_bits |= _CACHE_SUC; + + if (writeable) { + prot_bits |= _PAGE_WRITE; + if (write) + prot_bits |= __WRITEABLE; + } + + /* Disable dirty logging on HugePages */ + level = 0; + if (!fault_supports_huge_mapping(memslot, hva, write)) { + level = 0; + } else { + level = host_pfn_mapping_level(kvm, gfn, memslot); + if (level == 1) { + gfn = gfn & ~(PTRS_PER_PTE - 1); + pfn = pfn & ~(PTRS_PER_PTE - 1); + } + } + + /* Ensure page tables are allocated */ + ptep = kvm_populate_gpa(kvm, memcache, gpa, level); + new_pte = kvm_pfn_pte(pfn, __pgprot(prot_bits)); + if (level == 1) { + new_pte = kvm_pte_mkhuge(new_pte); + /* + * previous pmd entry is invalid_pte_table + * there is invalid tlb with small page + * need flush these invalid tlbs for current vcpu + */ + kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu); + ++kvm->stat.hugepages; + } else if (kvm_pte_huge(*ptep) && write) + ptep = kvm_split_huge(vcpu, ptep, gfn); + else + ++kvm->stat.pages; + kvm_set_pte(ptep, new_pte); + spin_unlock(&kvm->mmu_lock); + + if (prot_bits & _PAGE_DIRTY) { + mark_page_dirty_in_slot(kvm, memslot, gfn); + kvm_set_pfn_dirty(pfn); + } + + kvm_set_pfn_accessed(pfn); + kvm_release_pfn_clean(pfn); +out: + srcu_read_unlock(&kvm->srcu, srcu_idx); + return err; +} + +int kvm_handle_mm_fault(struct kvm_vcpu *vcpu, unsigned long gpa, bool write) +{ + int ret; + + ret = kvm_map_page(vcpu, gpa, write); + if (ret) + return ret; + + /* Invalidate this entry in the TLB */ + kvm_flush_tlb_gpa(vcpu, gpa); + + return 0; +} + +void kvm_arch_sync_dirty_log(struct kvm *kvm, struct kvm_memory_slot *memslot) +{ +} + +void kvm_arch_flush_remote_tlbs_memslot(struct kvm *kvm, + const struct kvm_memory_slot *memslot) +{ + kvm_flush_remote_tlbs(kvm); +} |