Implement LoongArch kvm mmu, it is used to switch gpa to hpa when guest
exit because of address translation exception.
This patch implement: allocating gpa page table, searching gpa from it,
and flushing guest gpa in the table.
Reviewed-by: Bibo Mao <maobibo@xxxxxxxxxxx>
Tested-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
Signed-off-by: Tianrui Zhao <zhaotianrui@xxxxxxxxxxx>
---
arch/loongarch/include/asm/kvm_mmu.h | 139 ++++
arch/loongarch/kvm/mmu.c | 914 +++++++++++++++++++++++++++
2 files changed, 1053 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..099bafc6f7
--- /dev/null
+++ b/arch/loongarch/include/asm/kvm_mmu.h
@@ -0,0 +1,139 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020-2023 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..80480df5f5
--- /dev/null
+++ b/arch/loongarch/kvm/mmu.c
@@ -0,0 +1,914 @@
+// 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 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);
+}
+
+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, unsigned long map_size, bool write)
+{
+ size_t size;
+ gpa_t gpa_start;
+ hva_t uaddr_start, uaddr_end;
+
+ /* 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_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_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 */
+ kvm_flush_tlb_gpa(vcpu, gpa);
+
+ return 0;
+}
+
+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);
+}
--
2.39.3
