[PATCH v21 18/29] LoongArch: KVM: Implement kvm mmu operations

[Tianrui Zhao]

Implement LoongArch kvm mmu, it is used to switch gpa to hpa when
guest exit because of address translation exception. This patch
implement allocate gpa page table, search gpa from it and flush guest
gpa in the table.

Reviewed-by: Bibo Mao <maobibo@xxxxxxxxxxx>
Signed-off-by: Tianrui Zhao <zhaotianrui@xxxxxxxxxxx>
---
 arch/loongarch/include/asm/kvm_mmu.h | 138 ++++
 arch/loongarch/kvm/mmu.c             | 922 +++++++++++++++++++++++++++
 2 files changed, 1060 insertions(+)
 create mode 100644 arch/loongarch/include/asm/kvm_mmu.h
 create mode 100644 arch/loongarch/kvm/mmu.c

diff --git a/arch/loongarch/include/asm/kvm_mmu.h b/arch/loongarch/include/asm/kvm_mmu.h
new file mode 100644
index 0000000000..641524a4f2
--- /dev/null
+++ b/arch/loongarch/include/asm/kvm_mmu.h
@@ -0,0 +1,138 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2022-2023 Loongson Technology Corporation Limited
+ */
+
+#ifndef __ASM_LOONGARCH_KVM_MMU_H__
+#define __ASM_LOONGARCH_KVM_MMU_H__
+
+#include <linux/kvm_host.h>
+#include <asm/pgalloc.h>
+#include <asm/tlb.h>
+
+/*
+ * KVM_MMU_CACHE_MIN_PAGES is the number of GPA page table translation levels
+ * for which pages need to be cached.
+ */
+#define KVM_MMU_CACHE_MIN_PAGES	(CONFIG_PGTABLE_LEVELS - 1)
+
+#define _KVM_FLUSH_PGTABLE	0x1
+#define _KVM_HAS_PGMASK		0x2
+#define kvm_pfn_pte(pfn, prot)	(((pfn) << PFN_PTE_SHIFT) | pgprot_val(prot))
+#define kvm_pte_pfn(x)		((phys_addr_t)((x & _PFN_MASK) >> PFN_PTE_SHIFT))
+
+typedef unsigned long kvm_pte_t;
+typedef struct kvm_ptw_ctx kvm_ptw_ctx;
+typedef int (*kvm_pte_ops)(kvm_pte_t *pte, phys_addr_t addr, kvm_ptw_ctx *ctx);
+
+struct kvm_ptw_ctx {
+	kvm_pte_ops     ops;
+	unsigned long   flag;
+	/* for kvm_arch_mmu_enable_log_dirty_pt_masked use */
+	unsigned long   mask;
+	unsigned long   gfn;
+
+	/* page walk mmu info */
+	unsigned int    level;
+	unsigned long   pgtable_shift;
+	unsigned long   invalid_entry;
+	unsigned long   *invalid_ptes;
+	unsigned int    *pte_shifts;
+	void		*opaque;
+
+	/* free pte table page list */
+	struct list_head list;
+};
+
+kvm_pte_t *kvm_pgd_alloc(void);
+
+static inline void kvm_set_pte(kvm_pte_t *ptep, kvm_pte_t val)
+{
+	WRITE_ONCE(*ptep, val);
+}
+
+static inline int kvm_pte_write(kvm_pte_t pte) { return pte & _PAGE_WRITE; }
+static inline int kvm_pte_dirty(kvm_pte_t pte) { return pte & _PAGE_DIRTY; }
+static inline int kvm_pte_young(kvm_pte_t pte) { return pte & _PAGE_ACCESSED; }
+static inline int kvm_pte_huge(kvm_pte_t pte) { return pte & _PAGE_HUGE; }
+
+static inline kvm_pte_t kvm_pte_mkyoung(kvm_pte_t pte)
+{
+	return pte | _PAGE_ACCESSED;
+}
+
+static inline kvm_pte_t kvm_pte_mkold(kvm_pte_t pte)
+{
+	return pte & ~_PAGE_ACCESSED;
+}
+
+static inline kvm_pte_t kvm_pte_mkdirty(kvm_pte_t pte)
+{
+	return pte | _PAGE_DIRTY;
+}
+
+static inline kvm_pte_t kvm_pte_mkclean(kvm_pte_t pte)
+{
+	return pte & ~_PAGE_DIRTY;
+}
+
+static inline kvm_pte_t kvm_pte_mkhuge(kvm_pte_t pte)
+{
+	return pte | _PAGE_HUGE;
+}
+
+static inline kvm_pte_t kvm_pte_mksmall(kvm_pte_t pte)
+{
+	return pte & ~_PAGE_HUGE;
+}
+
+static inline int kvm_need_flush(kvm_ptw_ctx *ctx)
+{
+	return ctx->flag & _KVM_FLUSH_PGTABLE;
+}
+
+static inline kvm_pte_t *kvm_pgtable_offset(kvm_ptw_ctx *ctx, kvm_pte_t *table,
+					phys_addr_t addr)
+{
+
+	return table + ((addr >> ctx->pgtable_shift) & (PTRS_PER_PTE - 1));
+}
+
+static inline phys_addr_t kvm_pgtable_addr_end(kvm_ptw_ctx *ctx,
+				phys_addr_t addr, phys_addr_t end)
+{
+	phys_addr_t boundary, size;
+
+	size = 0x1UL << ctx->pgtable_shift;
+	boundary = (addr + size) & ~(size - 1);
+	return (boundary - 1 < end - 1) ? boundary : end;
+}
+
+static inline int kvm_pte_present(kvm_ptw_ctx *ctx, kvm_pte_t *entry)
+{
+	if (!ctx || ctx->level == 0)
+		return !!(*entry & _PAGE_PRESENT);
+
+	return *entry != ctx->invalid_entry;
+}
+
+static inline int kvm_pte_none(kvm_ptw_ctx *ctx, kvm_pte_t *entry)
+{
+	return *entry == ctx->invalid_entry;
+}
+
+static inline void kvm_ptw_enter(kvm_ptw_ctx *ctx)
+{
+	ctx->level--;
+	ctx->pgtable_shift = ctx->pte_shifts[ctx->level];
+	ctx->invalid_entry = ctx->invalid_ptes[ctx->level];
+}
+
+static inline void kvm_ptw_exit(kvm_ptw_ctx *ctx)
+{
+	ctx->level++;
+	ctx->pgtable_shift = ctx->pte_shifts[ctx->level];
+	ctx->invalid_entry = ctx->invalid_ptes[ctx->level];
+}
+
+#endif /* __ASM_LOONGARCH_KVM_MMU_H__ */
diff --git a/arch/loongarch/kvm/mmu.c b/arch/loongarch/kvm/mmu.c
new file mode 100644
index 0000000000..cd73fcba92
--- /dev/null
+++ b/arch/loongarch/kvm/mmu.c
@@ -0,0 +1,922 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020-2023 Loongson Technology Corporation Limited
+ */
+
+#include <linux/highmem.h>
+#include <linux/page-flags.h>
+#include <linux/kvm_host.h>
+#include <linux/uaccess.h>
+#include <linux/hugetlb.h>
+#include <asm/mmu_context.h>
+#include <asm/pgalloc.h>
+#include <asm/tlb.h>
+#include <asm/kvm_mmu.h>
+
+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;
+}
+
+/*
+ * 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_mkclean_pte
+ * 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)
+{
+	kvm_pte_t val;
+	gfn_t offset;
+
+	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;
+	}
+
+	/*
+	 * Does not support eager_page_split
+	 * 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;
+}
+
+/**
+ * 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)
+{
+	kvm_pte_t *entry, *child;
+	phys_addr_t next, start, size;
+	struct list_head *list;
+	int ret;
+
+	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)
+{
+	kvm_pte_t *entry, *child;
+	phys_addr_t next, start, size;
+	struct list_head *list;
+	int ret;
+
+	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)
+{
+	kvm_pte_t *entry;
+	phys_addr_t next;
+	int ret;
+
+	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)
+{
+	struct list_head *pos, *temp;
+	kvm_ptw_ctx ctx;
+	int ret;
+
+	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);
+}
+
+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.ops = kvm_flush_pte;
+	/* do not free leaf pte table page */
+	ctx.flag = 0;
+	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)
+{
+	gpa_t gpa = range->start << PAGE_SHIFT;
+	kvm_pte_t *ptep;
+	kvm_pfn_t pfn = pte_pfn(range->arg.pte);
+	unsigned long prot_bits;
+
+	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.ops = kvm_mkold_pte;
+	ctx.flag = 0;
+	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)
+{
+	struct kvm *kvm = vcpu->kvm;
+	struct kvm_memory_slot *slot;
+	gfn_t gfn = gpa >> PAGE_SHIFT;
+	kvm_pte_t *ptep, changed, new;
+	kvm_pfn_t pfn = 0;
+	int ret = 0;
+
+	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, unsigned long map_size,
+				bool write)
+{
+	gpa_t gpa_start;
+	hva_t uaddr_start, uaddr_end;
+	size_t size;
+
+	/* Disable dirty logging on HugePages */
+	if (kvm_slot_dirty_track_enabled(memslot) && write)
+		return false;
+
+	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 for userspace and GPA cannot be mapped with stage-2
+	 * 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
+	 */
+	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;
+}
+
+/*
+ * 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_hva() 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_large() 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_pte_t *ptep, new_pte;
+	kvm_pfn_t pfn;
+	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_hva(kvm, mmu_seq, hva)) {
+		/*
+		 * 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, PMD_SIZE, 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 */
+	return kvm_flush_tlb_gpa(vcpu, gpa);
+}
+
+void kvm_arch_sync_dirty_log(struct kvm *kvm, struct kvm_memory_slot *memslot)
+{
+
+}
+
+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)
+{
+	return 0;
+}
+
+void kvm_arch_flush_remote_tlbs_memslot(struct kvm *kvm,
+					const struct kvm_memory_slot *memslot)
+{
+	kvm_flush_remote_tlbs(kvm);
+}
-- 
2.39.1