aboutsummaryrefslogtreecommitdiffstats
path: root/arch/x86/kvm/mmu/paging_tmpl.h
diff options
context:
space:
mode:
Diffstat (limited to 'arch/x86/kvm/mmu/paging_tmpl.h')
-rw-r--r--arch/x86/kvm/mmu/paging_tmpl.h1090
1 files changed, 1090 insertions, 0 deletions
diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
new file mode 100644
index 000000000000..97b21e7fd013
--- /dev/null
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -0,0 +1,1090 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Kernel-based Virtual Machine driver for Linux
+ *
+ * This module enables machines with Intel VT-x extensions to run virtual
+ * machines without emulation or binary translation.
+ *
+ * MMU support
+ *
+ * Copyright (C) 2006 Qumranet, Inc.
+ * Copyright 2010 Red Hat, Inc. and/or its affiliates.
+ *
+ * Authors:
+ * Yaniv Kamay <yaniv@qumranet.com>
+ * Avi Kivity <avi@qumranet.com>
+ */
+
+/*
+ * We need the mmu code to access both 32-bit and 64-bit guest ptes,
+ * so the code in this file is compiled twice, once per pte size.
+ */
+
+#if PTTYPE == 64
+ #define pt_element_t u64
+ #define guest_walker guest_walker64
+ #define FNAME(name) paging##64_##name
+ #define PT_BASE_ADDR_MASK PT64_BASE_ADDR_MASK
+ #define PT_LVL_ADDR_MASK(lvl) PT64_LVL_ADDR_MASK(lvl)
+ #define PT_LVL_OFFSET_MASK(lvl) PT64_LVL_OFFSET_MASK(lvl)
+ #define PT_INDEX(addr, level) PT64_INDEX(addr, level)
+ #define PT_LEVEL_BITS PT64_LEVEL_BITS
+ #define PT_GUEST_DIRTY_SHIFT PT_DIRTY_SHIFT
+ #define PT_GUEST_ACCESSED_SHIFT PT_ACCESSED_SHIFT
+ #define PT_HAVE_ACCESSED_DIRTY(mmu) true
+ #ifdef CONFIG_X86_64
+ #define PT_MAX_FULL_LEVELS 4
+ #define CMPXCHG cmpxchg
+ #else
+ #define CMPXCHG cmpxchg64
+ #define PT_MAX_FULL_LEVELS 2
+ #endif
+#elif PTTYPE == 32
+ #define pt_element_t u32
+ #define guest_walker guest_walker32
+ #define FNAME(name) paging##32_##name
+ #define PT_BASE_ADDR_MASK PT32_BASE_ADDR_MASK
+ #define PT_LVL_ADDR_MASK(lvl) PT32_LVL_ADDR_MASK(lvl)
+ #define PT_LVL_OFFSET_MASK(lvl) PT32_LVL_OFFSET_MASK(lvl)
+ #define PT_INDEX(addr, level) PT32_INDEX(addr, level)
+ #define PT_LEVEL_BITS PT32_LEVEL_BITS
+ #define PT_MAX_FULL_LEVELS 2
+ #define PT_GUEST_DIRTY_SHIFT PT_DIRTY_SHIFT
+ #define PT_GUEST_ACCESSED_SHIFT PT_ACCESSED_SHIFT
+ #define PT_HAVE_ACCESSED_DIRTY(mmu) true
+ #define CMPXCHG cmpxchg
+#elif PTTYPE == PTTYPE_EPT
+ #define pt_element_t u64
+ #define guest_walker guest_walkerEPT
+ #define FNAME(name) ept_##name
+ #define PT_BASE_ADDR_MASK PT64_BASE_ADDR_MASK
+ #define PT_LVL_ADDR_MASK(lvl) PT64_LVL_ADDR_MASK(lvl)
+ #define PT_LVL_OFFSET_MASK(lvl) PT64_LVL_OFFSET_MASK(lvl)
+ #define PT_INDEX(addr, level) PT64_INDEX(addr, level)
+ #define PT_LEVEL_BITS PT64_LEVEL_BITS
+ #define PT_GUEST_DIRTY_SHIFT 9
+ #define PT_GUEST_ACCESSED_SHIFT 8
+ #define PT_HAVE_ACCESSED_DIRTY(mmu) ((mmu)->ept_ad)
+ #define CMPXCHG cmpxchg64
+ #define PT_MAX_FULL_LEVELS 4
+#else
+ #error Invalid PTTYPE value
+#endif
+
+#define PT_GUEST_DIRTY_MASK (1 << PT_GUEST_DIRTY_SHIFT)
+#define PT_GUEST_ACCESSED_MASK (1 << PT_GUEST_ACCESSED_SHIFT)
+
+#define gpte_to_gfn_lvl FNAME(gpte_to_gfn_lvl)
+#define gpte_to_gfn(pte) gpte_to_gfn_lvl((pte), PT_PAGE_TABLE_LEVEL)
+
+/*
+ * The guest_walker structure emulates the behavior of the hardware page
+ * table walker.
+ */
+struct guest_walker {
+ int level;
+ unsigned max_level;
+ gfn_t table_gfn[PT_MAX_FULL_LEVELS];
+ pt_element_t ptes[PT_MAX_FULL_LEVELS];
+ pt_element_t prefetch_ptes[PTE_PREFETCH_NUM];
+ gpa_t pte_gpa[PT_MAX_FULL_LEVELS];
+ pt_element_t __user *ptep_user[PT_MAX_FULL_LEVELS];
+ bool pte_writable[PT_MAX_FULL_LEVELS];
+ unsigned pt_access;
+ unsigned pte_access;
+ gfn_t gfn;
+ struct x86_exception fault;
+};
+
+static gfn_t gpte_to_gfn_lvl(pt_element_t gpte, int lvl)
+{
+ return (gpte & PT_LVL_ADDR_MASK(lvl)) >> PAGE_SHIFT;
+}
+
+static inline void FNAME(protect_clean_gpte)(struct kvm_mmu *mmu, unsigned *access,
+ unsigned gpte)
+{
+ unsigned mask;
+
+ /* dirty bit is not supported, so no need to track it */
+ if (!PT_HAVE_ACCESSED_DIRTY(mmu))
+ return;
+
+ BUILD_BUG_ON(PT_WRITABLE_MASK != ACC_WRITE_MASK);
+
+ mask = (unsigned)~ACC_WRITE_MASK;
+ /* Allow write access to dirty gptes */
+ mask |= (gpte >> (PT_GUEST_DIRTY_SHIFT - PT_WRITABLE_SHIFT)) &
+ PT_WRITABLE_MASK;
+ *access &= mask;
+}
+
+static inline int FNAME(is_present_gpte)(unsigned long pte)
+{
+#if PTTYPE != PTTYPE_EPT
+ return pte & PT_PRESENT_MASK;
+#else
+ return pte & 7;
+#endif
+}
+
+static int FNAME(cmpxchg_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
+ pt_element_t __user *ptep_user, unsigned index,
+ pt_element_t orig_pte, pt_element_t new_pte)
+{
+ int npages;
+ pt_element_t ret;
+ pt_element_t *table;
+ struct page *page;
+
+ npages = get_user_pages_fast((unsigned long)ptep_user, 1, FOLL_WRITE, &page);
+ if (likely(npages == 1)) {
+ table = kmap_atomic(page);
+ ret = CMPXCHG(&table[index], orig_pte, new_pte);
+ kunmap_atomic(table);
+
+ kvm_release_page_dirty(page);
+ } else {
+ struct vm_area_struct *vma;
+ unsigned long vaddr = (unsigned long)ptep_user & PAGE_MASK;
+ unsigned long pfn;
+ unsigned long paddr;
+
+ down_read(&current->mm->mmap_sem);
+ vma = find_vma_intersection(current->mm, vaddr, vaddr + PAGE_SIZE);
+ if (!vma || !(vma->vm_flags & VM_PFNMAP)) {
+ up_read(&current->mm->mmap_sem);
+ return -EFAULT;
+ }
+ pfn = ((vaddr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
+ paddr = pfn << PAGE_SHIFT;
+ table = memremap(paddr, PAGE_SIZE, MEMREMAP_WB);
+ if (!table) {
+ up_read(&current->mm->mmap_sem);
+ return -EFAULT;
+ }
+ ret = CMPXCHG(&table[index], orig_pte, new_pte);
+ memunmap(table);
+ up_read(&current->mm->mmap_sem);
+ }
+
+ return (ret != orig_pte);
+}
+
+static bool FNAME(prefetch_invalid_gpte)(struct kvm_vcpu *vcpu,
+ struct kvm_mmu_page *sp, u64 *spte,
+ u64 gpte)
+{
+ if (is_rsvd_bits_set(vcpu->arch.mmu, gpte, PT_PAGE_TABLE_LEVEL))
+ goto no_present;
+
+ if (!FNAME(is_present_gpte)(gpte))
+ goto no_present;
+
+ /* if accessed bit is not supported prefetch non accessed gpte */
+ if (PT_HAVE_ACCESSED_DIRTY(vcpu->arch.mmu) &&
+ !(gpte & PT_GUEST_ACCESSED_MASK))
+ goto no_present;
+
+ return false;
+
+no_present:
+ drop_spte(vcpu->kvm, spte);
+ return true;
+}
+
+/*
+ * For PTTYPE_EPT, a page table can be executable but not readable
+ * on supported processors. Therefore, set_spte does not automatically
+ * set bit 0 if execute only is supported. Here, we repurpose ACC_USER_MASK
+ * to signify readability since it isn't used in the EPT case
+ */
+static inline unsigned FNAME(gpte_access)(u64 gpte)
+{
+ unsigned access;
+#if PTTYPE == PTTYPE_EPT
+ access = ((gpte & VMX_EPT_WRITABLE_MASK) ? ACC_WRITE_MASK : 0) |
+ ((gpte & VMX_EPT_EXECUTABLE_MASK) ? ACC_EXEC_MASK : 0) |
+ ((gpte & VMX_EPT_READABLE_MASK) ? ACC_USER_MASK : 0);
+#else
+ BUILD_BUG_ON(ACC_EXEC_MASK != PT_PRESENT_MASK);
+ BUILD_BUG_ON(ACC_EXEC_MASK != 1);
+ access = gpte & (PT_WRITABLE_MASK | PT_USER_MASK | PT_PRESENT_MASK);
+ /* Combine NX with P (which is set here) to get ACC_EXEC_MASK. */
+ access ^= (gpte >> PT64_NX_SHIFT);
+#endif
+
+ return access;
+}
+
+static int FNAME(update_accessed_dirty_bits)(struct kvm_vcpu *vcpu,
+ struct kvm_mmu *mmu,
+ struct guest_walker *walker,
+ int write_fault)
+{
+ unsigned level, index;
+ pt_element_t pte, orig_pte;
+ pt_element_t __user *ptep_user;
+ gfn_t table_gfn;
+ int ret;
+
+ /* dirty/accessed bits are not supported, so no need to update them */
+ if (!PT_HAVE_ACCESSED_DIRTY(mmu))
+ return 0;
+
+ for (level = walker->max_level; level >= walker->level; --level) {
+ pte = orig_pte = walker->ptes[level - 1];
+ table_gfn = walker->table_gfn[level - 1];
+ ptep_user = walker->ptep_user[level - 1];
+ index = offset_in_page(ptep_user) / sizeof(pt_element_t);
+ if (!(pte & PT_GUEST_ACCESSED_MASK)) {
+ trace_kvm_mmu_set_accessed_bit(table_gfn, index, sizeof(pte));
+ pte |= PT_GUEST_ACCESSED_MASK;
+ }
+ if (level == walker->level && write_fault &&
+ !(pte & PT_GUEST_DIRTY_MASK)) {
+ trace_kvm_mmu_set_dirty_bit(table_gfn, index, sizeof(pte));
+#if PTTYPE == PTTYPE_EPT
+ if (kvm_arch_write_log_dirty(vcpu))
+ return -EINVAL;
+#endif
+ pte |= PT_GUEST_DIRTY_MASK;
+ }
+ if (pte == orig_pte)
+ continue;
+
+ /*
+ * If the slot is read-only, simply do not process the accessed
+ * and dirty bits. This is the correct thing to do if the slot
+ * is ROM, and page tables in read-as-ROM/write-as-MMIO slots
+ * are only supported if the accessed and dirty bits are already
+ * set in the ROM (so that MMIO writes are never needed).
+ *
+ * Note that NPT does not allow this at all and faults, since
+ * it always wants nested page table entries for the guest
+ * page tables to be writable. And EPT works but will simply
+ * overwrite the read-only memory to set the accessed and dirty
+ * bits.
+ */
+ if (unlikely(!walker->pte_writable[level - 1]))
+ continue;
+
+ ret = FNAME(cmpxchg_gpte)(vcpu, mmu, ptep_user, index, orig_pte, pte);
+ if (ret)
+ return ret;
+
+ kvm_vcpu_mark_page_dirty(vcpu, table_gfn);
+ walker->ptes[level - 1] = pte;
+ }
+ return 0;
+}
+
+static inline unsigned FNAME(gpte_pkeys)(struct kvm_vcpu *vcpu, u64 gpte)
+{
+ unsigned pkeys = 0;
+#if PTTYPE == 64
+ pte_t pte = {.pte = gpte};
+
+ pkeys = pte_flags_pkey(pte_flags(pte));
+#endif
+ return pkeys;
+}
+
+/*
+ * Fetch a guest pte for a guest virtual address
+ */
+static int FNAME(walk_addr_generic)(struct guest_walker *walker,
+ struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
+ gva_t addr, u32 access)
+{
+ int ret;
+ pt_element_t pte;
+ pt_element_t __user *uninitialized_var(ptep_user);
+ gfn_t table_gfn;
+ u64 pt_access, pte_access;
+ unsigned index, accessed_dirty, pte_pkey;
+ unsigned nested_access;
+ gpa_t pte_gpa;
+ bool have_ad;
+ int offset;
+ u64 walk_nx_mask = 0;
+ const int write_fault = access & PFERR_WRITE_MASK;
+ const int user_fault = access & PFERR_USER_MASK;
+ const int fetch_fault = access & PFERR_FETCH_MASK;
+ u16 errcode = 0;
+ gpa_t real_gpa;
+ gfn_t gfn;
+
+ trace_kvm_mmu_pagetable_walk(addr, access);
+retry_walk:
+ walker->level = mmu->root_level;
+ pte = mmu->get_cr3(vcpu);
+ have_ad = PT_HAVE_ACCESSED_DIRTY(mmu);
+
+#if PTTYPE == 64
+ walk_nx_mask = 1ULL << PT64_NX_SHIFT;
+ if (walker->level == PT32E_ROOT_LEVEL) {
+ pte = mmu->get_pdptr(vcpu, (addr >> 30) & 3);
+ trace_kvm_mmu_paging_element(pte, walker->level);
+ if (!FNAME(is_present_gpte)(pte))
+ goto error;
+ --walker->level;
+ }
+#endif
+ walker->max_level = walker->level;
+ ASSERT(!(is_long_mode(vcpu) && !is_pae(vcpu)));
+
+ /*
+ * FIXME: on Intel processors, loads of the PDPTE registers for PAE paging
+ * by the MOV to CR instruction are treated as reads and do not cause the
+ * processor to set the dirty flag in any EPT paging-structure entry.
+ */
+ nested_access = (have_ad ? PFERR_WRITE_MASK : 0) | PFERR_USER_MASK;
+
+ pte_access = ~0;
+ ++walker->level;
+
+ do {
+ gfn_t real_gfn;
+ unsigned long host_addr;
+
+ pt_access = pte_access;
+ --walker->level;
+
+ index = PT_INDEX(addr, walker->level);
+ table_gfn = gpte_to_gfn(pte);
+ offset = index * sizeof(pt_element_t);
+ pte_gpa = gfn_to_gpa(table_gfn) + offset;
+
+ BUG_ON(walker->level < 1);
+ walker->table_gfn[walker->level - 1] = table_gfn;
+ walker->pte_gpa[walker->level - 1] = pte_gpa;
+
+ real_gfn = mmu->translate_gpa(vcpu, gfn_to_gpa(table_gfn),
+ nested_access,
+ &walker->fault);
+
+ /*
+ * FIXME: This can happen if emulation (for of an INS/OUTS
+ * instruction) triggers a nested page fault. The exit
+ * qualification / exit info field will incorrectly have
+ * "guest page access" as the nested page fault's cause,
+ * instead of "guest page structure access". To fix this,
+ * the x86_exception struct should be augmented with enough
+ * information to fix the exit_qualification or exit_info_1
+ * fields.
+ */
+ if (unlikely(real_gfn == UNMAPPED_GVA))
+ return 0;
+
+ real_gfn = gpa_to_gfn(real_gfn);
+
+ host_addr = kvm_vcpu_gfn_to_hva_prot(vcpu, real_gfn,
+ &walker->pte_writable[walker->level - 1]);
+ if (unlikely(kvm_is_error_hva(host_addr)))
+ goto error;
+
+ ptep_user = (pt_element_t __user *)((void *)host_addr + offset);
+ if (unlikely(__copy_from_user(&pte, ptep_user, sizeof(pte))))
+ goto error;
+ walker->ptep_user[walker->level - 1] = ptep_user;
+
+ trace_kvm_mmu_paging_element(pte, walker->level);
+
+ /*
+ * Inverting the NX it lets us AND it like other
+ * permission bits.
+ */
+ pte_access = pt_access & (pte ^ walk_nx_mask);
+
+ if (unlikely(!FNAME(is_present_gpte)(pte)))
+ goto error;
+
+ if (unlikely(is_rsvd_bits_set(mmu, pte, walker->level))) {
+ errcode = PFERR_RSVD_MASK | PFERR_PRESENT_MASK;
+ goto error;
+ }
+
+ walker->ptes[walker->level - 1] = pte;
+ } while (!is_last_gpte(mmu, walker->level, pte));
+
+ pte_pkey = FNAME(gpte_pkeys)(vcpu, pte);
+ accessed_dirty = have_ad ? pte_access & PT_GUEST_ACCESSED_MASK : 0;
+
+ /* Convert to ACC_*_MASK flags for struct guest_walker. */
+ walker->pt_access = FNAME(gpte_access)(pt_access ^ walk_nx_mask);
+ walker->pte_access = FNAME(gpte_access)(pte_access ^ walk_nx_mask);
+ errcode = permission_fault(vcpu, mmu, walker->pte_access, pte_pkey, access);
+ if (unlikely(errcode))
+ goto error;
+
+ gfn = gpte_to_gfn_lvl(pte, walker->level);
+ gfn += (addr & PT_LVL_OFFSET_MASK(walker->level)) >> PAGE_SHIFT;
+
+ if (PTTYPE == 32 && walker->level == PT_DIRECTORY_LEVEL && is_cpuid_PSE36())
+ gfn += pse36_gfn_delta(pte);
+
+ real_gpa = mmu->translate_gpa(vcpu, gfn_to_gpa(gfn), access, &walker->fault);
+ if (real_gpa == UNMAPPED_GVA)
+ return 0;
+
+ walker->gfn = real_gpa >> PAGE_SHIFT;
+
+ if (!write_fault)
+ FNAME(protect_clean_gpte)(mmu, &walker->pte_access, pte);
+ else
+ /*
+ * On a write fault, fold the dirty bit into accessed_dirty.
+ * For modes without A/D bits support accessed_dirty will be
+ * always clear.
+ */
+ accessed_dirty &= pte >>
+ (PT_GUEST_DIRTY_SHIFT - PT_GUEST_ACCESSED_SHIFT);
+
+ if (unlikely(!accessed_dirty)) {
+ ret = FNAME(update_accessed_dirty_bits)(vcpu, mmu, walker, write_fault);
+ if (unlikely(ret < 0))
+ goto error;
+ else if (ret)
+ goto retry_walk;
+ }
+
+ pgprintk("%s: pte %llx pte_access %x pt_access %x\n",
+ __func__, (u64)pte, walker->pte_access, walker->pt_access);
+ return 1;
+
+error:
+ errcode |= write_fault | user_fault;
+ if (fetch_fault && (mmu->nx ||
+ kvm_read_cr4_bits(vcpu, X86_CR4_SMEP)))
+ errcode |= PFERR_FETCH_MASK;
+
+ walker->fault.vector = PF_VECTOR;
+ walker->fault.error_code_valid = true;
+ walker->fault.error_code = errcode;
+
+#if PTTYPE == PTTYPE_EPT
+ /*
+ * Use PFERR_RSVD_MASK in error_code to to tell if EPT
+ * misconfiguration requires to be injected. The detection is
+ * done by is_rsvd_bits_set() above.
+ *
+ * We set up the value of exit_qualification to inject:
+ * [2:0] - Derive from the access bits. The exit_qualification might be
+ * out of date if it is serving an EPT misconfiguration.
+ * [5:3] - Calculated by the page walk of the guest EPT page tables
+ * [7:8] - Derived from [7:8] of real exit_qualification
+ *
+ * The other bits are set to 0.
+ */
+ if (!(errcode & PFERR_RSVD_MASK)) {
+ vcpu->arch.exit_qualification &= 0x180;
+ if (write_fault)
+ vcpu->arch.exit_qualification |= EPT_VIOLATION_ACC_WRITE;
+ if (user_fault)
+ vcpu->arch.exit_qualification |= EPT_VIOLATION_ACC_READ;
+ if (fetch_fault)
+ vcpu->arch.exit_qualification |= EPT_VIOLATION_ACC_INSTR;
+ vcpu->arch.exit_qualification |= (pte_access & 0x7) << 3;
+ }
+#endif
+ walker->fault.address = addr;
+ walker->fault.nested_page_fault = mmu != vcpu->arch.walk_mmu;
+
+ trace_kvm_mmu_walker_error(walker->fault.error_code);
+ return 0;
+}
+
+static int FNAME(walk_addr)(struct guest_walker *walker,
+ struct kvm_vcpu *vcpu, gva_t addr, u32 access)
+{
+ return FNAME(walk_addr_generic)(walker, vcpu, vcpu->arch.mmu, addr,
+ access);
+}
+
+#if PTTYPE != PTTYPE_EPT
+static int FNAME(walk_addr_nested)(struct guest_walker *walker,
+ struct kvm_vcpu *vcpu, gva_t addr,
+ u32 access)
+{
+ return FNAME(walk_addr_generic)(walker, vcpu, &vcpu->arch.nested_mmu,
+ addr, access);
+}
+#endif
+
+static bool
+FNAME(prefetch_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
+ u64 *spte, pt_element_t gpte, bool no_dirty_log)
+{
+ unsigned pte_access;
+ gfn_t gfn;
+ kvm_pfn_t pfn;
+
+ if (FNAME(prefetch_invalid_gpte)(vcpu, sp, spte, gpte))
+ return false;
+
+ pgprintk("%s: gpte %llx spte %p\n", __func__, (u64)gpte, spte);
+
+ gfn = gpte_to_gfn(gpte);
+ pte_access = sp->role.access & FNAME(gpte_access)(gpte);
+ FNAME(protect_clean_gpte)(vcpu->arch.mmu, &pte_access, gpte);
+ pfn = pte_prefetch_gfn_to_pfn(vcpu, gfn,
+ no_dirty_log && (pte_access & ACC_WRITE_MASK));
+ if (is_error_pfn(pfn))
+ return false;
+
+ /*
+ * we call mmu_set_spte() with host_writable = true because
+ * pte_prefetch_gfn_to_pfn always gets a writable pfn.
+ */
+ mmu_set_spte(vcpu, spte, pte_access, 0, PT_PAGE_TABLE_LEVEL, gfn, pfn,
+ true, true);
+
+ kvm_release_pfn_clean(pfn);
+ return true;
+}
+
+static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
+ u64 *spte, const void *pte)
+{
+ pt_element_t gpte = *(const pt_element_t *)pte;
+
+ FNAME(prefetch_gpte)(vcpu, sp, spte, gpte, false);
+}
+
+static bool FNAME(gpte_changed)(struct kvm_vcpu *vcpu,
+ struct guest_walker *gw, int level)
+{
+ pt_element_t curr_pte;
+ gpa_t base_gpa, pte_gpa = gw->pte_gpa[level - 1];
+ u64 mask;
+ int r, index;
+
+ if (level == PT_PAGE_TABLE_LEVEL) {
+ mask = PTE_PREFETCH_NUM * sizeof(pt_element_t) - 1;
+ base_gpa = pte_gpa & ~mask;
+ index = (pte_gpa - base_gpa) / sizeof(pt_element_t);
+
+ r = kvm_vcpu_read_guest_atomic(vcpu, base_gpa,
+ gw->prefetch_ptes, sizeof(gw->prefetch_ptes));
+ curr_pte = gw->prefetch_ptes[index];
+ } else
+ r = kvm_vcpu_read_guest_atomic(vcpu, pte_gpa,
+ &curr_pte, sizeof(curr_pte));
+
+ return r || curr_pte != gw->ptes[level - 1];
+}
+
+static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu, struct guest_walker *gw,
+ u64 *sptep)
+{
+ struct kvm_mmu_page *sp;
+ pt_element_t *gptep = gw->prefetch_ptes;
+ u64 *spte;
+ int i;
+
+ sp = page_header(__pa(sptep));
+
+ if (sp->role.level > PT_PAGE_TABLE_LEVEL)
+ return;
+
+ if (sp->role.direct)
+ return __direct_pte_prefetch(vcpu, sp, sptep);
+
+ i = (sptep - sp->spt) & ~(PTE_PREFETCH_NUM - 1);
+ spte = sp->spt + i;
+
+ for (i = 0; i < PTE_PREFETCH_NUM; i++, spte++) {
+ if (spte == sptep)
+ continue;
+
+ if (is_shadow_present_pte(*spte))
+ continue;
+
+ if (!FNAME(prefetch_gpte)(vcpu, sp, spte, gptep[i], true))
+ break;
+ }
+}
+
+/*
+ * Fetch a shadow pte for a specific level in the paging hierarchy.
+ * If the guest tries to write a write-protected page, we need to
+ * emulate this operation, return 1 to indicate this case.
+ */
+static int FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
+ struct guest_walker *gw,
+ int write_fault, int hlevel,
+ kvm_pfn_t pfn, bool map_writable, bool prefault,
+ bool lpage_disallowed)
+{
+ struct kvm_mmu_page *sp = NULL;
+ struct kvm_shadow_walk_iterator it;
+ unsigned direct_access, access = gw->pt_access;
+ int top_level, ret;
+ gfn_t gfn, base_gfn;
+
+ direct_access = gw->pte_access;
+
+ top_level = vcpu->arch.mmu->root_level;
+ if (top_level == PT32E_ROOT_LEVEL)
+ top_level = PT32_ROOT_LEVEL;
+ /*
+ * Verify that the top-level gpte is still there. Since the page
+ * is a root page, it is either write protected (and cannot be
+ * changed from now on) or it is invalid (in which case, we don't
+ * really care if it changes underneath us after this point).
+ */
+ if (FNAME(gpte_changed)(vcpu, gw, top_level))
+ goto out_gpte_changed;
+
+ if (!VALID_PAGE(vcpu->arch.mmu->root_hpa))
+ goto out_gpte_changed;
+
+ for (shadow_walk_init(&it, vcpu, addr);
+ shadow_walk_okay(&it) && it.level > gw->level;
+ shadow_walk_next(&it)) {
+ gfn_t table_gfn;
+
+ clear_sp_write_flooding_count(it.sptep);
+ drop_large_spte(vcpu, it.sptep);
+
+ sp = NULL;
+ if (!is_shadow_present_pte(*it.sptep)) {
+ table_gfn = gw->table_gfn[it.level - 2];
+ sp = kvm_mmu_get_page(vcpu, table_gfn, addr, it.level-1,
+ false, access);
+ }
+
+ /*
+ * Verify that the gpte in the page we've just write
+ * protected is still there.
+ */
+ if (FNAME(gpte_changed)(vcpu, gw, it.level - 1))
+ goto out_gpte_changed;
+
+ if (sp)
+ link_shadow_page(vcpu, it.sptep, sp);
+ }
+
+ /*
+ * FNAME(page_fault) might have clobbered the bottom bits of
+ * gw->gfn, restore them from the virtual address.
+ */
+ gfn = gw->gfn | ((addr & PT_LVL_OFFSET_MASK(gw->level)) >> PAGE_SHIFT);
+ base_gfn = gfn;
+
+ trace_kvm_mmu_spte_requested(addr, gw->level, pfn);
+
+ for (; shadow_walk_okay(&it); shadow_walk_next(&it)) {
+ clear_sp_write_flooding_count(it.sptep);
+
+ /*
+ * We cannot overwrite existing page tables with an NX
+ * large page, as the leaf could be executable.
+ */
+ disallowed_hugepage_adjust(it, gfn, &pfn, &hlevel);
+
+ base_gfn = gfn & ~(KVM_PAGES_PER_HPAGE(it.level) - 1);
+ if (it.level == hlevel)
+ break;
+
+ validate_direct_spte(vcpu, it.sptep, direct_access);
+
+ drop_large_spte(vcpu, it.sptep);
+
+ if (!is_shadow_present_pte(*it.sptep)) {
+ sp = kvm_mmu_get_page(vcpu, base_gfn, addr,
+ it.level - 1, true, direct_access);
+ link_shadow_page(vcpu, it.sptep, sp);
+ if (lpage_disallowed)
+ account_huge_nx_page(vcpu->kvm, sp);
+ }
+ }
+
+ ret = mmu_set_spte(vcpu, it.sptep, gw->pte_access, write_fault,
+ it.level, base_gfn, pfn, prefault, map_writable);
+ FNAME(pte_prefetch)(vcpu, gw, it.sptep);
+ ++vcpu->stat.pf_fixed;
+ return ret;
+
+out_gpte_changed:
+ return RET_PF_RETRY;
+}
+
+ /*
+ * To see whether the mapped gfn can write its page table in the current
+ * mapping.
+ *
+ * It is the helper function of FNAME(page_fault). When guest uses large page
+ * size to map the writable gfn which is used as current page table, we should
+ * force kvm to use small page size to map it because new shadow page will be
+ * created when kvm establishes shadow page table that stop kvm using large
+ * page size. Do it early can avoid unnecessary #PF and emulation.
+ *
+ * @write_fault_to_shadow_pgtable will return true if the fault gfn is
+ * currently used as its page table.
+ *
+ * Note: the PDPT page table is not checked for PAE-32 bit guest. It is ok
+ * since the PDPT is always shadowed, that means, we can not use large page
+ * size to map the gfn which is used as PDPT.
+ */
+static bool
+FNAME(is_self_change_mapping)(struct kvm_vcpu *vcpu,
+ struct guest_walker *walker, int user_fault,
+ bool *write_fault_to_shadow_pgtable)
+{
+ int level;
+ gfn_t mask = ~(KVM_PAGES_PER_HPAGE(walker->level) - 1);
+ bool self_changed = false;
+
+ if (!(walker->pte_access & ACC_WRITE_MASK ||
+ (!is_write_protection(vcpu) && !user_fault)))
+ return false;
+
+ for (level = walker->level; level <= walker->max_level; level++) {
+ gfn_t gfn = walker->gfn ^ walker->table_gfn[level - 1];
+
+ self_changed |= !(gfn & mask);
+ *write_fault_to_shadow_pgtable |= !gfn;
+ }
+
+ return self_changed;
+}
+
+/*
+ * Page fault handler. There are several causes for a page fault:
+ * - there is no shadow pte for the guest pte
+ * - write access through a shadow pte marked read only so that we can set
+ * the dirty bit
+ * - write access to a shadow pte marked read only so we can update the page
+ * dirty bitmap, when userspace requests it
+ * - mmio access; in this case we will never install a present shadow pte
+ * - normal guest page fault due to the guest pte marked not present, not
+ * writable, or not executable
+ *
+ * Returns: 1 if we need to emulate the instruction, 0 otherwise, or
+ * a negative value on error.
+ */
+static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code,
+ bool prefault)
+{
+ int write_fault = error_code & PFERR_WRITE_MASK;
+ int user_fault = error_code & PFERR_USER_MASK;
+ struct guest_walker walker;
+ int r;
+ kvm_pfn_t pfn;
+ int level = PT_PAGE_TABLE_LEVEL;
+ unsigned long mmu_seq;
+ bool map_writable, is_self_change_mapping;
+ bool lpage_disallowed = (error_code & PFERR_FETCH_MASK) &&
+ is_nx_huge_page_enabled();
+ bool force_pt_level = lpage_disallowed;
+
+ pgprintk("%s: addr %lx err %x\n", __func__, addr, error_code);
+
+ r = mmu_topup_memory_caches(vcpu);
+ if (r)
+ return r;
+
+ /*
+ * If PFEC.RSVD is set, this is a shadow page fault.
+ * The bit needs to be cleared before walking guest page tables.
+ */
+ error_code &= ~PFERR_RSVD_MASK;
+
+ /*
+ * Look up the guest pte for the faulting address.
+ */
+ r = FNAME(walk_addr)(&walker, vcpu, addr, error_code);
+
+ /*
+ * The page is not mapped by the guest. Let the guest handle it.
+ */
+ if (!r) {
+ pgprintk("%s: guest page fault\n", __func__);
+ if (!prefault)
+ inject_page_fault(vcpu, &walker.fault);
+
+ return RET_PF_RETRY;
+ }
+
+ if (page_fault_handle_page_track(vcpu, error_code, walker.gfn)) {
+ shadow_page_table_clear_flood(vcpu, addr);
+ return RET_PF_EMULATE;
+ }
+
+ vcpu->arch.write_fault_to_shadow_pgtable = false;
+
+ is_self_change_mapping = FNAME(is_self_change_mapping)(vcpu,
+ &walker, user_fault, &vcpu->arch.write_fault_to_shadow_pgtable);
+
+ if (walker.level >= PT_DIRECTORY_LEVEL && !is_self_change_mapping) {
+ level = mapping_level(vcpu, walker.gfn, &force_pt_level);
+ if (likely(!force_pt_level)) {
+ level = min(walker.level, level);
+ walker.gfn = walker.gfn & ~(KVM_PAGES_PER_HPAGE(level) - 1);
+ }
+ } else
+ force_pt_level = true;
+
+ mmu_seq = vcpu->kvm->mmu_notifier_seq;
+ smp_rmb();
+
+ if (try_async_pf(vcpu, prefault, walker.gfn, addr, &pfn, write_fault,
+ &map_writable))
+ return RET_PF_RETRY;
+
+ if (handle_abnormal_pfn(vcpu, addr, walker.gfn, pfn, walker.pte_access, &r))
+ return r;
+
+ /*
+ * Do not change pte_access if the pfn is a mmio page, otherwise
+ * we will cache the incorrect access into mmio spte.
+ */
+ if (write_fault && !(walker.pte_access & ACC_WRITE_MASK) &&
+ !is_write_protection(vcpu) && !user_fault &&
+ !is_noslot_pfn(pfn)) {
+ walker.pte_access |= ACC_WRITE_MASK;
+ walker.pte_access &= ~ACC_USER_MASK;
+
+ /*
+ * If we converted a user page to a kernel page,
+ * so that the kernel can write to it when cr0.wp=0,
+ * then we should prevent the kernel from executing it
+ * if SMEP is enabled.
+ */
+ if (kvm_read_cr4_bits(vcpu, X86_CR4_SMEP))
+ walker.pte_access &= ~ACC_EXEC_MASK;
+ }
+
+ r = RET_PF_RETRY;
+ spin_lock(&vcpu->kvm->mmu_lock);
+ if (mmu_notifier_retry(vcpu->kvm, mmu_seq))
+ goto out_unlock;
+
+ kvm_mmu_audit(vcpu, AUDIT_PRE_PAGE_FAULT);
+ if (make_mmu_pages_available(vcpu) < 0)
+ goto out_unlock;
+ if (!force_pt_level)
+ transparent_hugepage_adjust(vcpu, walker.gfn, &pfn, &level);
+ r = FNAME(fetch)(vcpu, addr, &walker, write_fault,
+ level, pfn, map_writable, prefault, lpage_disallowed);
+ kvm_mmu_audit(vcpu, AUDIT_POST_PAGE_FAULT);
+
+out_unlock:
+ spin_unlock(&vcpu->kvm->mmu_lock);
+ kvm_release_pfn_clean(pfn);
+ return r;
+}
+
+static gpa_t FNAME(get_level1_sp_gpa)(struct kvm_mmu_page *sp)
+{
+ int offset = 0;
+
+ WARN_ON(sp->role.level != PT_PAGE_TABLE_LEVEL);
+
+ if (PTTYPE == 32)
+ offset = sp->role.quadrant << PT64_LEVEL_BITS;
+
+ return gfn_to_gpa(sp->gfn) + offset * sizeof(pt_element_t);
+}
+
+static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva, hpa_t root_hpa)
+{
+ struct kvm_shadow_walk_iterator iterator;
+ struct kvm_mmu_page *sp;
+ int level;
+ u64 *sptep;
+
+ vcpu_clear_mmio_info(vcpu, gva);
+
+ /*
+ * No need to check return value here, rmap_can_add() can
+ * help us to skip pte prefetch later.
+ */
+ mmu_topup_memory_caches(vcpu);
+
+ if (!VALID_PAGE(root_hpa)) {
+ WARN_ON(1);
+ return;
+ }
+
+ spin_lock(&vcpu->kvm->mmu_lock);
+ for_each_shadow_entry_using_root(vcpu, root_hpa, gva, iterator) {
+ level = iterator.level;
+ sptep = iterator.sptep;
+
+ sp = page_header(__pa(sptep));
+ if (is_last_spte(*sptep, level)) {
+ pt_element_t gpte;
+ gpa_t pte_gpa;
+
+ if (!sp->unsync)
+ break;
+
+ pte_gpa = FNAME(get_level1_sp_gpa)(sp);
+ pte_gpa += (sptep - sp->spt) * sizeof(pt_element_t);
+
+ if (mmu_page_zap_pte(vcpu->kvm, sp, sptep))
+ kvm_flush_remote_tlbs_with_address(vcpu->kvm,
+ sp->gfn, KVM_PAGES_PER_HPAGE(sp->role.level));
+
+ if (!rmap_can_add(vcpu))
+ break;
+
+ if (kvm_vcpu_read_guest_atomic(vcpu, pte_gpa, &gpte,
+ sizeof(pt_element_t)))
+ break;
+
+ FNAME(update_pte)(vcpu, sp, sptep, &gpte);
+ }
+
+ if (!is_shadow_present_pte(*sptep) || !sp->unsync_children)
+ break;
+ }
+ spin_unlock(&vcpu->kvm->mmu_lock);
+}
+
+static gpa_t FNAME(gva_to_gpa)(struct kvm_vcpu *vcpu, gva_t vaddr, u32 access,
+ struct x86_exception *exception)
+{
+ struct guest_walker walker;
+ gpa_t gpa = UNMAPPED_GVA;
+ int r;
+
+ r = FNAME(walk_addr)(&walker, vcpu, vaddr, access);
+
+ if (r) {
+ gpa = gfn_to_gpa(walker.gfn);
+ gpa |= vaddr & ~PAGE_MASK;
+ } else if (exception)
+ *exception = walker.fault;
+
+ return gpa;
+}
+
+#if PTTYPE != PTTYPE_EPT
+static gpa_t FNAME(gva_to_gpa_nested)(struct kvm_vcpu *vcpu, gva_t vaddr,
+ u32 access,
+ struct x86_exception *exception)
+{
+ struct guest_walker walker;
+ gpa_t gpa = UNMAPPED_GVA;
+ int r;
+
+ r = FNAME(walk_addr_nested)(&walker, vcpu, vaddr, access);
+
+ if (r) {
+ gpa = gfn_to_gpa(walker.gfn);
+ gpa |= vaddr & ~PAGE_MASK;
+ } else if (exception)
+ *exception = walker.fault;
+
+ return gpa;
+}
+#endif
+
+/*
+ * Using the cached information from sp->gfns is safe because:
+ * - The spte has a reference to the struct page, so the pfn for a given gfn
+ * can't change unless all sptes pointing to it are nuked first.
+ *
+ * Note:
+ * We should flush all tlbs if spte is dropped even though guest is
+ * responsible for it. Since if we don't, kvm_mmu_notifier_invalidate_page
+ * and kvm_mmu_notifier_invalidate_range_start detect the mapping page isn't
+ * used by guest then tlbs are not flushed, so guest is allowed to access the
+ * freed pages.
+ * And we increase kvm->tlbs_dirty to delay tlbs flush in this case.
+ */
+static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
+{
+ int i, nr_present = 0;
+ bool host_writable;
+ gpa_t first_pte_gpa;
+ int set_spte_ret = 0;
+
+ /* direct kvm_mmu_page can not be unsync. */
+ BUG_ON(sp->role.direct);
+
+ first_pte_gpa = FNAME(get_level1_sp_gpa)(sp);
+
+ for (i = 0; i < PT64_ENT_PER_PAGE; i++) {
+ unsigned pte_access;
+ pt_element_t gpte;
+ gpa_t pte_gpa;
+ gfn_t gfn;
+
+ if (!sp->spt[i])
+ continue;
+
+ pte_gpa = first_pte_gpa + i * sizeof(pt_element_t);
+
+ if (kvm_vcpu_read_guest_atomic(vcpu, pte_gpa, &gpte,
+ sizeof(pt_element_t)))
+ return 0;
+
+ if (FNAME(prefetch_invalid_gpte)(vcpu, sp, &sp->spt[i], gpte)) {
+ /*
+ * Update spte before increasing tlbs_dirty to make
+ * sure no tlb flush is lost after spte is zapped; see
+ * the comments in kvm_flush_remote_tlbs().
+ */
+ smp_wmb();
+ vcpu->kvm->tlbs_dirty++;
+ continue;
+ }
+
+ gfn = gpte_to_gfn(gpte);
+ pte_access = sp->role.access;
+ pte_access &= FNAME(gpte_access)(gpte);
+ FNAME(protect_clean_gpte)(vcpu->arch.mmu, &pte_access, gpte);
+
+ if (sync_mmio_spte(vcpu, &sp->spt[i], gfn, pte_access,
+ &nr_present))
+ continue;
+
+ if (gfn != sp->gfns[i]) {
+ drop_spte(vcpu->kvm, &sp->spt[i]);
+ /*
+ * The same as above where we are doing
+ * prefetch_invalid_gpte().
+ */
+ smp_wmb();
+ vcpu->kvm->tlbs_dirty++;
+ continue;
+ }
+
+ nr_present++;
+
+ host_writable = sp->spt[i] & SPTE_HOST_WRITEABLE;
+
+ set_spte_ret |= set_spte(vcpu, &sp->spt[i],
+ pte_access, PT_PAGE_TABLE_LEVEL,
+ gfn, spte_to_pfn(sp->spt[i]),
+ true, false, host_writable);
+ }
+
+ if (set_spte_ret & SET_SPTE_NEED_REMOTE_TLB_FLUSH)
+ kvm_flush_remote_tlbs(vcpu->kvm);
+
+ return nr_present;
+}
+
+#undef pt_element_t
+#undef guest_walker
+#undef FNAME
+#undef PT_BASE_ADDR_MASK
+#undef PT_INDEX
+#undef PT_LVL_ADDR_MASK
+#undef PT_LVL_OFFSET_MASK
+#undef PT_LEVEL_BITS
+#undef PT_MAX_FULL_LEVELS
+#undef gpte_to_gfn
+#undef gpte_to_gfn_lvl
+#undef CMPXCHG
+#undef PT_GUEST_ACCESSED_MASK
+#undef PT_GUEST_DIRTY_MASK
+#undef PT_GUEST_DIRTY_SHIFT
+#undef PT_GUEST_ACCESSED_SHIFT
+#undef PT_HAVE_ACCESSED_DIRTY
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.