diff options
Diffstat (limited to 'arch/x86/kvm/mmu/tdp_mmu.c')
| -rw-r--r-- | arch/x86/kvm/mmu/tdp_mmu.c | 1992 |
1 files changed, 1992 insertions, 0 deletions
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c new file mode 100644 index 000000000000..9c26038f6b77 --- /dev/null +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -0,0 +1,1992 @@ +// SPDX-License-Identifier: GPL-2.0 +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include "mmu.h" +#include "mmu_internal.h" +#include "mmutrace.h" +#include "tdp_iter.h" +#include "tdp_mmu.h" +#include "spte.h" + +#include <asm/cmpxchg.h> +#include <trace/events/kvm.h> + +/* Initializes the TDP MMU for the VM, if enabled. */ +void kvm_mmu_init_tdp_mmu(struct kvm *kvm) +{ + INIT_LIST_HEAD(&kvm->arch.tdp_mmu_roots); + spin_lock_init(&kvm->arch.tdp_mmu_pages_lock); +} + +/* Arbitrarily returns true so that this may be used in if statements. */ +static __always_inline bool kvm_lockdep_assert_mmu_lock_held(struct kvm *kvm, + bool shared) +{ + if (shared) + lockdep_assert_held_read(&kvm->mmu_lock); + else + lockdep_assert_held_write(&kvm->mmu_lock); + + return true; +} + +void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm) +{ + /* + * Invalidate all roots, which besides the obvious, schedules all roots + * for zapping and thus puts the TDP MMU's reference to each root, i.e. + * ultimately frees all roots. + */ + kvm_tdp_mmu_invalidate_roots(kvm, KVM_VALID_ROOTS); + kvm_tdp_mmu_zap_invalidated_roots(kvm, false); + +#ifdef CONFIG_KVM_PROVE_MMU + KVM_MMU_WARN_ON(atomic64_read(&kvm->arch.tdp_mmu_pages)); +#endif + WARN_ON(!list_empty(&kvm->arch.tdp_mmu_roots)); + + /* + * Ensure that all the outstanding RCU callbacks to free shadow pages + * can run before the VM is torn down. Putting the last reference to + * zapped roots will create new callbacks. + */ + rcu_barrier(); +} + +static void tdp_mmu_free_sp(struct kvm_mmu_page *sp) +{ + free_page((unsigned long)sp->external_spt); + free_page((unsigned long)sp->spt); + kmem_cache_free(mmu_page_header_cache, sp); +} + +/* + * This is called through call_rcu in order to free TDP page table memory + * safely with respect to other kernel threads that may be operating on + * the memory. + * By only accessing TDP MMU page table memory in an RCU read critical + * section, and freeing it after a grace period, lockless access to that + * memory won't use it after it is freed. + */ +static void tdp_mmu_free_sp_rcu_callback(struct rcu_head *head) +{ + struct kvm_mmu_page *sp = container_of(head, struct kvm_mmu_page, + rcu_head); + + tdp_mmu_free_sp(sp); +} + +void kvm_tdp_mmu_put_root(struct kvm *kvm, struct kvm_mmu_page *root) +{ + if (!refcount_dec_and_test(&root->tdp_mmu_root_count)) + return; + + /* + * The TDP MMU itself holds a reference to each root until the root is + * explicitly invalidated, i.e. the final reference should be never be + * put for a valid root. + */ + KVM_BUG_ON(!is_tdp_mmu_page(root) || !root->role.invalid, kvm); + + spin_lock(&kvm->arch.tdp_mmu_pages_lock); + list_del_rcu(&root->link); + spin_unlock(&kvm->arch.tdp_mmu_pages_lock); + call_rcu(&root->rcu_head, tdp_mmu_free_sp_rcu_callback); +} + +static bool tdp_mmu_root_match(struct kvm_mmu_page *root, + enum kvm_tdp_mmu_root_types types) +{ + if (WARN_ON_ONCE(!(types & KVM_VALID_ROOTS))) + return false; + + if (root->role.invalid && !(types & KVM_INVALID_ROOTS)) + return false; + + if (likely(!is_mirror_sp(root))) + return types & KVM_DIRECT_ROOTS; + return types & KVM_MIRROR_ROOTS; +} + +/* + * Returns the next root after @prev_root (or the first root if @prev_root is + * NULL) that matches with @types. A reference to the returned root is + * acquired, and the reference to @prev_root is released (the caller obviously + * must hold a reference to @prev_root if it's non-NULL). + * + * Roots that doesn't match with @types are skipped. + * + * Returns NULL if the end of tdp_mmu_roots was reached. + */ +static struct kvm_mmu_page *tdp_mmu_next_root(struct kvm *kvm, + struct kvm_mmu_page *prev_root, + enum kvm_tdp_mmu_root_types types) +{ + struct kvm_mmu_page *next_root; + + /* + * While the roots themselves are RCU-protected, fields such as + * role.invalid are protected by mmu_lock. + */ + lockdep_assert_held(&kvm->mmu_lock); + + rcu_read_lock(); + + if (prev_root) + next_root = list_next_or_null_rcu(&kvm->arch.tdp_mmu_roots, + &prev_root->link, + typeof(*prev_root), link); + else + next_root = list_first_or_null_rcu(&kvm->arch.tdp_mmu_roots, + typeof(*next_root), link); + + while (next_root) { + if (tdp_mmu_root_match(next_root, types) && + kvm_tdp_mmu_get_root(next_root)) + break; + + next_root = list_next_or_null_rcu(&kvm->arch.tdp_mmu_roots, + &next_root->link, typeof(*next_root), link); + } + + rcu_read_unlock(); + + if (prev_root) + kvm_tdp_mmu_put_root(kvm, prev_root); + + return next_root; +} + +/* + * Note: this iterator gets and puts references to the roots it iterates over. + * This makes it safe to release the MMU lock and yield within the loop, but + * if exiting the loop early, the caller must drop the reference to the most + * recent root. (Unless keeping a live reference is desirable.) + * + * If shared is set, this function is operating under the MMU lock in read + * mode. + */ +#define __for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _types) \ + for (_root = tdp_mmu_next_root(_kvm, NULL, _types); \ + ({ lockdep_assert_held(&(_kvm)->mmu_lock); }), _root; \ + _root = tdp_mmu_next_root(_kvm, _root, _types)) \ + if (_as_id >= 0 && kvm_mmu_page_as_id(_root) != _as_id) { \ + } else + +#define for_each_valid_tdp_mmu_root_yield_safe(_kvm, _root, _as_id) \ + __for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, KVM_VALID_ROOTS) + +#define for_each_tdp_mmu_root_yield_safe(_kvm, _root) \ + for (_root = tdp_mmu_next_root(_kvm, NULL, KVM_ALL_ROOTS); \ + ({ lockdep_assert_held(&(_kvm)->mmu_lock); }), _root; \ + _root = tdp_mmu_next_root(_kvm, _root, KVM_ALL_ROOTS)) + +/* + * Iterate over all TDP MMU roots. Requires that mmu_lock be held for write, + * the implication being that any flow that holds mmu_lock for read is + * inherently yield-friendly and should use the yield-safe variant above. + * Holding mmu_lock for write obviates the need for RCU protection as the list + * is guaranteed to be stable. + */ +#define __for_each_tdp_mmu_root(_kvm, _root, _as_id, _types) \ + list_for_each_entry(_root, &_kvm->arch.tdp_mmu_roots, link) \ + if (kvm_lockdep_assert_mmu_lock_held(_kvm, false) && \ + ((_as_id >= 0 && kvm_mmu_page_as_id(_root) != _as_id) || \ + !tdp_mmu_root_match((_root), (_types)))) { \ + } else + +/* + * Iterate over all TDP MMU roots in an RCU read-side critical section. + * It is safe to iterate over the SPTEs under the root, but their values will + * be unstable, so all writes must be atomic. As this routine is meant to be + * used without holding the mmu_lock at all, any bits that are flipped must + * be reflected in kvm_tdp_mmu_spte_need_atomic_write(). + */ +#define for_each_tdp_mmu_root_rcu(_kvm, _root, _as_id, _types) \ + list_for_each_entry_rcu(_root, &_kvm->arch.tdp_mmu_roots, link) \ + if ((_as_id >= 0 && kvm_mmu_page_as_id(_root) != _as_id) || \ + !tdp_mmu_root_match((_root), (_types))) { \ + } else + +#define for_each_valid_tdp_mmu_root(_kvm, _root, _as_id) \ + __for_each_tdp_mmu_root(_kvm, _root, _as_id, KVM_VALID_ROOTS) + +static struct kvm_mmu_page *tdp_mmu_alloc_sp(struct kvm_vcpu *vcpu) +{ + struct kvm_mmu_page *sp; + + sp = kvm_mmu_memory_cache_alloc(&vcpu->arch.mmu_page_header_cache); + sp->spt = kvm_mmu_memory_cache_alloc(&vcpu->arch.mmu_shadow_page_cache); + + return sp; +} + +static void tdp_mmu_init_sp(struct kvm_mmu_page *sp, tdp_ptep_t sptep, + gfn_t gfn, union kvm_mmu_page_role role) +{ + INIT_LIST_HEAD(&sp->possible_nx_huge_page_link); + + set_page_private(virt_to_page(sp->spt), (unsigned long)sp); + + sp->role = role; + sp->gfn = gfn; + sp->ptep = sptep; + sp->tdp_mmu_page = true; + + trace_kvm_mmu_get_page(sp, true); +} + +static void tdp_mmu_init_child_sp(struct kvm_mmu_page *child_sp, + struct tdp_iter *iter) +{ + struct kvm_mmu_page *parent_sp; + union kvm_mmu_page_role role; + + parent_sp = sptep_to_sp(rcu_dereference(iter->sptep)); + + role = parent_sp->role; + role.level--; + + tdp_mmu_init_sp(child_sp, iter->sptep, iter->gfn, role); +} + +void kvm_tdp_mmu_alloc_root(struct kvm_vcpu *vcpu, bool mirror) +{ + struct kvm_mmu *mmu = vcpu->arch.mmu; + union kvm_mmu_page_role role = mmu->root_role; + int as_id = kvm_mmu_role_as_id(role); + struct kvm *kvm = vcpu->kvm; + struct kvm_mmu_page *root; + + if (mirror) + role.is_mirror = true; + + /* + * Check for an existing root before acquiring the pages lock to avoid + * unnecessary serialization if multiple vCPUs are loading a new root. + * E.g. when bringing up secondary vCPUs, KVM will already have created + * a valid root on behalf of the primary vCPU. + */ + read_lock(&kvm->mmu_lock); + + for_each_valid_tdp_mmu_root_yield_safe(kvm, root, as_id) { + if (root->role.word == role.word) + goto out_read_unlock; + } + + spin_lock(&kvm->arch.tdp_mmu_pages_lock); + + /* + * Recheck for an existing root after acquiring the pages lock, another + * vCPU may have raced ahead and created a new usable root. Manually + * walk the list of roots as the standard macros assume that the pages + * lock is *not* held. WARN if grabbing a reference to a usable root + * fails, as the last reference to a root can only be put *after* the + * root has been invalidated, which requires holding mmu_lock for write. + */ + list_for_each_entry(root, &kvm->arch.tdp_mmu_roots, link) { + if (root->role.word == role.word && + !WARN_ON_ONCE(!kvm_tdp_mmu_get_root(root))) + goto out_spin_unlock; + } + + root = tdp_mmu_alloc_sp(vcpu); + tdp_mmu_init_sp(root, NULL, 0, role); + + /* + * TDP MMU roots are kept until they are explicitly invalidated, either + * by a memslot update or by the destruction of the VM. Initialize the + * refcount to two; one reference for the vCPU, and one reference for + * the TDP MMU itself, which is held until the root is invalidated and + * is ultimately put by kvm_tdp_mmu_zap_invalidated_roots(). + */ + refcount_set(&root->tdp_mmu_root_count, 2); + list_add_rcu(&root->link, &kvm->arch.tdp_mmu_roots); + +out_spin_unlock: + spin_unlock(&kvm->arch.tdp_mmu_pages_lock); +out_read_unlock: + read_unlock(&kvm->mmu_lock); + /* + * Note, KVM_REQ_MMU_FREE_OBSOLETE_ROOTS will prevent entering the guest + * and actually consuming the root if it's invalidated after dropping + * mmu_lock, and the root can't be freed as this vCPU holds a reference. + */ + if (mirror) { + mmu->mirror_root_hpa = __pa(root->spt); + } else { + mmu->root.hpa = __pa(root->spt); + mmu->root.pgd = 0; + } +} + +static void handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn, + u64 old_spte, u64 new_spte, int level, + bool shared); + +static void tdp_account_mmu_page(struct kvm *kvm, struct kvm_mmu_page *sp) +{ + kvm_account_pgtable_pages((void *)sp->spt, +1); +#ifdef CONFIG_KVM_PROVE_MMU + atomic64_inc(&kvm->arch.tdp_mmu_pages); +#endif +} + +static void tdp_unaccount_mmu_page(struct kvm *kvm, struct kvm_mmu_page *sp) +{ + kvm_account_pgtable_pages((void *)sp->spt, -1); +#ifdef CONFIG_KVM_PROVE_MMU + atomic64_dec(&kvm->arch.tdp_mmu_pages); +#endif +} + +/** + * tdp_mmu_unlink_sp() - Remove a shadow page from the list of used pages + * + * @kvm: kvm instance + * @sp: the page to be removed + */ +static void tdp_mmu_unlink_sp(struct kvm *kvm, struct kvm_mmu_page *sp) +{ + tdp_unaccount_mmu_page(kvm, sp); + + if (!sp->nx_huge_page_disallowed) + return; + + spin_lock(&kvm->arch.tdp_mmu_pages_lock); + sp->nx_huge_page_disallowed = false; + untrack_possible_nx_huge_page(kvm, sp, KVM_TDP_MMU); + spin_unlock(&kvm->arch.tdp_mmu_pages_lock); +} + +static void remove_external_spte(struct kvm *kvm, gfn_t gfn, u64 old_spte, + int level) +{ + /* + * External (TDX) SPTEs are limited to PG_LEVEL_4K, and external + * PTs are removed in a special order, involving free_external_spt(). + * But remove_external_spte() will be called on non-leaf PTEs via + * __tdp_mmu_zap_root(), so avoid the error the former would return + * in this case. + */ + if (!is_last_spte(old_spte, level)) + return; + + /* Zapping leaf spte is allowed only when write lock is held. */ + lockdep_assert_held_write(&kvm->mmu_lock); + + kvm_x86_call(remove_external_spte)(kvm, gfn, level, old_spte); +} + +/** + * handle_removed_pt() - handle a page table removed from the TDP structure + * + * @kvm: kvm instance + * @pt: the page removed from the paging structure + * @shared: This operation may not be running under the exclusive use + * of the MMU lock and the operation must synchronize with other + * threads that might be modifying SPTEs. + * + * Given a page table that has been removed from the TDP paging structure, + * iterates through the page table to clear SPTEs and free child page tables. + * + * Note that pt is passed in as a tdp_ptep_t, but it does not need RCU + * protection. Since this thread removed it from the paging structure, + * this thread will be responsible for ensuring the page is freed. Hence the + * early rcu_dereferences in the function. + */ +static void handle_removed_pt(struct kvm *kvm, tdp_ptep_t pt, bool shared) +{ + struct kvm_mmu_page *sp = sptep_to_sp(rcu_dereference(pt)); + int level = sp->role.level; + gfn_t base_gfn = sp->gfn; + int i; + + trace_kvm_mmu_prepare_zap_page(sp); + + tdp_mmu_unlink_sp(kvm, sp); + + for (i = 0; i < SPTE_ENT_PER_PAGE; i++) { + tdp_ptep_t sptep = pt + i; + gfn_t gfn = base_gfn + i * KVM_PAGES_PER_HPAGE(level); + u64 old_spte; + + if (shared) { + /* + * Set the SPTE to a nonpresent value that other + * threads will not overwrite. If the SPTE was + * already marked as frozen then another thread + * handling a page fault could overwrite it, so + * set the SPTE until it is set from some other + * value to the frozen SPTE value. + */ + for (;;) { + old_spte = kvm_tdp_mmu_write_spte_atomic(sptep, FROZEN_SPTE); + if (!is_frozen_spte(old_spte)) + break; + cpu_relax(); + } + } else { + /* + * If the SPTE is not MMU-present, there is no backing + * page associated with the SPTE and so no side effects + * that need to be recorded, and exclusive ownership of + * mmu_lock ensures the SPTE can't be made present. + * Note, zapping MMIO SPTEs is also unnecessary as they + * are guarded by the memslots generation, not by being + * unreachable. + */ + old_spte = kvm_tdp_mmu_read_spte(sptep); + if (!is_shadow_present_pte(old_spte)) + continue; + + /* + * Use the common helper instead of a raw WRITE_ONCE as + * the SPTE needs to be updated atomically if it can be + * modified by a different vCPU outside of mmu_lock. + * Even though the parent SPTE is !PRESENT, the TLB + * hasn't yet been flushed, and both Intel and AMD + * document that A/D assists can use upper-level PxE + * entries that are cached in the TLB, i.e. the CPU can + * still access the page and mark it dirty. + * + * No retry is needed in the atomic update path as the + * sole concern is dropping a Dirty bit, i.e. no other + * task can zap/remove the SPTE as mmu_lock is held for + * write. Marking the SPTE as a frozen SPTE is not + * strictly necessary for the same reason, but using + * the frozen SPTE value keeps the shared/exclusive + * paths consistent and allows the handle_changed_spte() + * call below to hardcode the new value to FROZEN_SPTE. + * + * Note, even though dropping a Dirty bit is the only + * scenario where a non-atomic update could result in a + * functional bug, simply checking the Dirty bit isn't + * sufficient as a fast page fault could read the upper + * level SPTE before it is zapped, and then make this + * target SPTE writable, resume the guest, and set the + * Dirty bit between reading the SPTE above and writing + * it here. + */ + old_spte = kvm_tdp_mmu_write_spte(sptep, old_spte, + FROZEN_SPTE, level); + } + handle_changed_spte(kvm, kvm_mmu_page_as_id(sp), gfn, + old_spte, FROZEN_SPTE, level, shared); + + if (is_mirror_sp(sp)) { + KVM_BUG_ON(shared, kvm); + remove_external_spte(kvm, gfn, old_spte, level); + } + } + + if (is_mirror_sp(sp) && + WARN_ON(kvm_x86_call(free_external_spt)(kvm, base_gfn, sp->role.level, + sp->external_spt))) { + /* + * Failed to free page table page in mirror page table and + * there is nothing to do further. + * Intentionally leak the page to prevent the kernel from + * accessing the encrypted page. + */ + sp->external_spt = NULL; + } + + call_rcu(&sp->rcu_head, tdp_mmu_free_sp_rcu_callback); +} + +static void *get_external_spt(gfn_t gfn, u64 new_spte, int level) +{ + if (is_shadow_present_pte(new_spte) && !is_last_spte(new_spte, level)) { + struct kvm_mmu_page *sp = spte_to_child_sp(new_spte); + + WARN_ON_ONCE(sp->role.level + 1 != level); + WARN_ON_ONCE(sp->gfn != gfn); + return sp->external_spt; + } + + return NULL; +} + +static int __must_check set_external_spte_present(struct kvm *kvm, tdp_ptep_t sptep, + gfn_t gfn, u64 old_spte, + u64 new_spte, int level) +{ + bool was_present = is_shadow_present_pte(old_spte); + bool is_present = is_shadow_present_pte(new_spte); + bool is_leaf = is_present && is_last_spte(new_spte, level); + int ret = 0; + + KVM_BUG_ON(was_present, kvm); + + lockdep_assert_held(&kvm->mmu_lock); + /* + * We need to lock out other updates to the SPTE until the external + * page table has been modified. Use FROZEN_SPTE similar to + * the zapping case. + */ + if (!try_cmpxchg64(rcu_dereference(sptep), &old_spte, FROZEN_SPTE)) + return -EBUSY; + + /* + * Use different call to either set up middle level + * external page table, or leaf. + */ + if (is_leaf) { + ret = kvm_x86_call(set_external_spte)(kvm, gfn, level, new_spte); + } else { + void *external_spt = get_external_spt(gfn, new_spte, level); + + KVM_BUG_ON(!external_spt, kvm); + ret = kvm_x86_call(link_external_spt)(kvm, gfn, level, external_spt); + } + if (ret) + __kvm_tdp_mmu_write_spte(sptep, old_spte); + else + __kvm_tdp_mmu_write_spte(sptep, new_spte); + return ret; +} + +/** + * handle_changed_spte - handle bookkeeping associated with an SPTE change + * @kvm: kvm instance + * @as_id: the address space of the paging structure the SPTE was a part of + * @gfn: the base GFN that was mapped by the SPTE + * @old_spte: The value of the SPTE before the change + * @new_spte: The value of the SPTE after the change + * @level: the level of the PT the SPTE is part of in the paging structure + * @shared: This operation may not be running under the exclusive use of + * the MMU lock and the operation must synchronize with other + * threads that might be modifying SPTEs. + * + * Handle bookkeeping that might result from the modification of a SPTE. Note, + * dirty logging updates are handled in common code, not here (see make_spte() + * and fast_pf_fix_direct_spte()). + */ +static void handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn, + u64 old_spte, u64 new_spte, int level, + bool shared) +{ + bool was_present = is_shadow_present_pte(old_spte); + bool is_present = is_shadow_present_pte(new_spte); + bool was_leaf = was_present && is_last_spte(old_spte, level); + bool is_leaf = is_present && is_last_spte(new_spte, level); + bool pfn_changed = spte_to_pfn(old_spte) != spte_to_pfn(new_spte); + + WARN_ON_ONCE(level > PT64_ROOT_MAX_LEVEL); + WARN_ON_ONCE(level < PG_LEVEL_4K); + WARN_ON_ONCE(gfn & (KVM_PAGES_PER_HPAGE(level) - 1)); + + /* + * If this warning were to trigger it would indicate that there was a + * missing MMU notifier or a race with some notifier handler. + * A present, leaf SPTE should never be directly replaced with another + * present leaf SPTE pointing to a different PFN. A notifier handler + * should be zapping the SPTE before the main MM's page table is + * changed, or the SPTE should be zeroed, and the TLBs flushed by the + * thread before replacement. + */ + if (was_leaf && is_leaf && pfn_changed) { + pr_err("Invalid SPTE change: cannot replace a present leaf\n" + "SPTE with another present leaf SPTE mapping a\n" + "different PFN!\n" + "as_id: %d gfn: %llx old_spte: %llx new_spte: %llx level: %d", + as_id, gfn, old_spte, new_spte, level); + + /* + * Crash the host to prevent error propagation and guest data + * corruption. + */ + BUG(); + } + + if (old_spte == new_spte) + return; + + trace_kvm_tdp_mmu_spte_changed(as_id, gfn, level, old_spte, new_spte); + + if (is_leaf) + check_spte_writable_invariants(new_spte); + + /* + * The only times a SPTE should be changed from a non-present to + * non-present state is when an MMIO entry is installed/modified/ + * removed. In that case, there is nothing to do here. + */ + if (!was_present && !is_present) { + /* + * If this change does not involve a MMIO SPTE or frozen SPTE, + * it is unexpected. Log the change, though it should not + * impact the guest since both the former and current SPTEs + * are nonpresent. + */ + if (WARN_ON_ONCE(!is_mmio_spte(kvm, old_spte) && + !is_mmio_spte(kvm, new_spte) && + !is_frozen_spte(new_spte))) + pr_err("Unexpected SPTE change! Nonpresent SPTEs\n" + "should not be replaced with another,\n" + "different nonpresent SPTE, unless one or both\n" + "are MMIO SPTEs, or the new SPTE is\n" + "a temporary frozen SPTE.\n" + "as_id: %d gfn: %llx old_spte: %llx new_spte: %llx level: %d", + as_id, gfn, old_spte, new_spte, level); + return; + } + + if (is_leaf != was_leaf) + kvm_update_page_stats(kvm, level, is_leaf ? 1 : -1); + + /* + * Recursively handle child PTs if the change removed a subtree from + * the paging structure. Note the WARN on the PFN changing without the + * SPTE being converted to a hugepage (leaf) or being zapped. Shadow + * pages are kernel allocations and should never be migrated. + */ + if (was_present && !was_leaf && + (is_leaf || !is_present || WARN_ON_ONCE(pfn_changed))) + handle_removed_pt(kvm, spte_to_child_pt(old_spte, level), shared); +} + +static inline int __must_check __tdp_mmu_set_spte_atomic(struct kvm *kvm, + struct tdp_iter *iter, + u64 new_spte) +{ + /* + * The caller is responsible for ensuring the old SPTE is not a FROZEN + * SPTE. KVM should never attempt to zap or manipulate a FROZEN SPTE, + * and pre-checking before inserting a new SPTE is advantageous as it + * avoids unnecessary work. + */ + WARN_ON_ONCE(iter->yielded || is_frozen_spte(iter->old_spte)); + + if (is_mirror_sptep(iter->sptep) && !is_frozen_spte(new_spte)) { + int ret; + + /* + * Users of atomic zapping don't operate on mirror roots, + * so don't handle it and bug the VM if it's seen. + */ + if (KVM_BUG_ON(!is_shadow_present_pte(new_spte), kvm)) + return -EBUSY; + + ret = set_external_spte_present(kvm, iter->sptep, iter->gfn, + iter->old_spte, new_spte, iter->level); + if (ret) + return ret; + } else { + u64 *sptep = rcu_dereference(iter->sptep); + + /* + * Note, fast_pf_fix_direct_spte() can also modify TDP MMU SPTEs + * and does not hold the mmu_lock. On failure, i.e. if a + * different logical CPU modified the SPTE, try_cmpxchg64() + * updates iter->old_spte with the current value, so the caller + * operates on fresh data, e.g. if it retries + * tdp_mmu_set_spte_atomic() + */ + if (!try_cmpxchg64(sptep, &iter->old_spte, new_spte)) + return -EBUSY; + } + + return 0; +} + +/* + * tdp_mmu_set_spte_atomic - Set a TDP MMU SPTE atomically + * and handle the associated bookkeeping. Do not mark the page dirty + * in KVM's dirty bitmaps. + * + * If setting the SPTE fails because it has changed, iter->old_spte will be + * refreshed to the current value of the spte. + * + * @kvm: kvm instance + * @iter: a tdp_iter instance currently on the SPTE that should be set + * @new_spte: The value the SPTE should be set to + * Return: + * * 0 - If the SPTE was set. + * * -EBUSY - If the SPTE cannot be set. In this case this function will have + * no side-effects other than setting iter->old_spte to the last + * known value of the spte. + */ +static inline int __must_check tdp_mmu_set_spte_atomic(struct kvm *kvm, + struct tdp_iter *iter, + u64 new_spte) +{ + int ret; + + lockdep_assert_held_read(&kvm->mmu_lock); + + ret = __tdp_mmu_set_spte_atomic(kvm, iter, new_spte); + if (ret) + return ret; + + handle_changed_spte(kvm, iter->as_id, iter->gfn, iter->old_spte, + new_spte, iter->level, true); + + return 0; +} + +/* + * tdp_mmu_set_spte - Set a TDP MMU SPTE and handle the associated bookkeeping + * @kvm: KVM instance + * @as_id: Address space ID, i.e. regular vs. SMM + * @sptep: Pointer to the SPTE + * @old_spte: The current value of the SPTE + * @new_spte: The new value that will be set for the SPTE + * @gfn: The base GFN that was (or will be) mapped by the SPTE + * @level: The level _containing_ the SPTE (its parent PT's level) + * + * Returns the old SPTE value, which _may_ be different than @old_spte if the + * SPTE had voldatile bits. + */ +static u64 tdp_mmu_set_spte(struct kvm *kvm, int as_id, tdp_ptep_t sptep, + u64 old_spte, u64 new_spte, gfn_t gfn, int level) +{ + lockdep_assert_held_write(&kvm->mmu_lock); + + /* + * No thread should be using this function to set SPTEs to or from the + * temporary frozen SPTE value. + * If operating under the MMU lock in read mode, tdp_mmu_set_spte_atomic + * should be used. If operating under the MMU lock in write mode, the + * use of the frozen SPTE should not be necessary. + */ + WARN_ON_ONCE(is_frozen_spte(old_spte) || is_frozen_spte(new_spte)); + + old_spte = kvm_tdp_mmu_write_spte(sptep, old_spte, new_spte, level); + + handle_changed_spte(kvm, as_id, gfn, old_spte, new_spte, level, false); + + /* + * Users that do non-atomic setting of PTEs don't operate on mirror + * roots, so don't handle it and bug the VM if it's seen. + */ + if (is_mirror_sptep(sptep)) { + KVM_BUG_ON(is_shadow_present_pte(new_spte), kvm); + remove_external_spte(kvm, gfn, old_spte, level); + } + + return old_spte; +} + +static inline void tdp_mmu_iter_set_spte(struct kvm *kvm, struct tdp_iter *iter, + u64 new_spte) +{ + WARN_ON_ONCE(iter->yielded); + iter->old_spte = tdp_mmu_set_spte(kvm, iter->as_id, iter->sptep, + iter->old_spte, new_spte, + iter->gfn, iter->level); +} + +#define tdp_root_for_each_pte(_iter, _kvm, _root, _start, _end) \ + for_each_tdp_pte(_iter, _kvm, _root, _start, _end) + +#define tdp_root_for_each_leaf_pte(_iter, _kvm, _root, _start, _end) \ + tdp_root_for_each_pte(_iter, _kvm, _root, _start, _end) \ + if (!is_shadow_present_pte(_iter.old_spte) || \ + !is_last_spte(_iter.old_spte, _iter.level)) \ + continue; \ + else + +static inline bool __must_check tdp_mmu_iter_need_resched(struct kvm *kvm, + struct tdp_iter *iter) +{ + if (!need_resched() && !rwlock_needbreak(&kvm->mmu_lock)) + return false; + + /* Ensure forward progress has been made before yielding. */ + return iter->next_last_level_gfn != iter->yielded_gfn; +} + +/* + * Yield if the MMU lock is contended or this thread needs to return control + * to the scheduler. + * + * If this function should yield and flush is set, it will perform a remote + * TLB flush before yielding. + * + * If this function yields, iter->yielded is set and the caller must skip to + * the next iteration, where tdp_iter_next() will reset the tdp_iter's walk + * over the paging structures to allow the iterator to continue its traversal + * from the paging structure root. + * + * Returns true if this function yielded. + */ +static inline bool __must_check tdp_mmu_iter_cond_resched(struct kvm *kvm, + struct tdp_iter *iter, + bool flush, bool shared) +{ + KVM_MMU_WARN_ON(iter->yielded); + + if (!tdp_mmu_iter_need_resched(kvm, iter)) + return false; + + if (flush) + kvm_flush_remote_tlbs(kvm); + + rcu_read_unlock(); + + if (shared) + cond_resched_rwlock_read(&kvm->mmu_lock); + else + cond_resched_rwlock_write(&kvm->mmu_lock); + + rcu_read_lock(); + + WARN_ON_ONCE(iter->gfn > iter->next_last_level_gfn); + + iter->yielded = true; + return true; +} + +static inline gfn_t tdp_mmu_max_gfn_exclusive(void) +{ + /* + * Bound TDP MMU walks at host.MAXPHYADDR. KVM disallows memslots with + * a gpa range that would exceed the max gfn, and KVM does not create + * MMIO SPTEs for "impossible" gfns, instead sending such accesses down + * the slow emulation path every time. + */ + return kvm_mmu_max_gfn() + 1; +} + +static void __tdp_mmu_zap_root(struct kvm *kvm, struct kvm_mmu_page *root, + bool shared, int zap_level) +{ + struct tdp_iter iter; + + for_each_tdp_pte_min_level_all(iter, root, zap_level) { +retry: + if (tdp_mmu_iter_cond_resched(kvm, &iter, false, shared)) + continue; + + if (!is_shadow_present_pte(iter.old_spte)) + continue; + + if (iter.level > zap_level) + continue; + + if (!shared) + tdp_mmu_iter_set_spte(kvm, &iter, SHADOW_NONPRESENT_VALUE); + else if (tdp_mmu_set_spte_atomic(kvm, &iter, SHADOW_NONPRESENT_VALUE)) + goto retry; + } +} + +static void tdp_mmu_zap_root(struct kvm *kvm, struct kvm_mmu_page *root, + bool shared) +{ + + /* + * The root must have an elevated refcount so that it's reachable via + * mmu_notifier callbacks, which allows this path to yield and drop + * mmu_lock. When handling an unmap/release mmu_notifier command, KVM + * must drop all references to relevant pages prior to completing the + * callback. Dropping mmu_lock with an unreachable root would result + * in zapping SPTEs after a relevant mmu_notifier callback completes + * and lead to use-after-free as zapping a SPTE triggers "writeback" of + * dirty accessed bits to the SPTE's associated struct page. + */ + WARN_ON_ONCE(!refcount_read(&root->tdp_mmu_root_count)); + + kvm_lockdep_assert_mmu_lock_held(kvm, shared); + + rcu_read_lock(); + + /* + * Zap roots in multiple passes of decreasing granularity, i.e. zap at + * 4KiB=>2MiB=>1GiB=>root, in order to better honor need_resched() (all + * preempt models) or mmu_lock contention (full or real-time models). + * Zapping at finer granularity marginally increases the total time of + * the zap, but in most cases the zap itself isn't latency sensitive. + * + * If KVM is configured to prove the MMU, skip the 4KiB and 2MiB zaps + * in order to mimic the page fault path, which can replace a 1GiB page + * table with an equivalent 1GiB hugepage, i.e. can get saddled with + * zapping a 1GiB region that's fully populated with 4KiB SPTEs. This + * allows verifying that KVM can safely zap 1GiB regions, e.g. without + * inducing RCU stalls, without relying on a relatively rare event + * (zapping roots is orders of magnitude more common). Note, because + * zapping a SP recurses on its children, stepping down to PG_LEVEL_4K + * in the iterator itself is unnecessary. + */ + if (!IS_ENABLED(CONFIG_KVM_PROVE_MMU)) { + __tdp_mmu_zap_root(kvm, root, shared, PG_LEVEL_4K); + __tdp_mmu_zap_root(kvm, root, shared, PG_LEVEL_2M); + } + __tdp_mmu_zap_root(kvm, root, shared, PG_LEVEL_1G); + __tdp_mmu_zap_root(kvm, root, shared, root->role.level); + + rcu_read_unlock(); +} + +bool kvm_tdp_mmu_zap_possible_nx_huge_page(struct kvm *kvm, + struct kvm_mmu_page *sp) +{ + struct tdp_iter iter = { + .old_spte = sp->ptep ? kvm_tdp_mmu_read_spte(sp->ptep) : 0, + .sptep = sp->ptep, + .level = sp->role.level + 1, + .gfn = sp->gfn, + .as_id = kvm_mmu_page_as_id(sp), + }; + + lockdep_assert_held_read(&kvm->mmu_lock); + + if (WARN_ON_ONCE(!is_tdp_mmu_page(sp))) + return false; + + /* + * Root shadow pages don't have a parent page table and thus no + * associated entry, but they can never be possible NX huge pages. + */ + if (WARN_ON_ONCE(!sp->ptep)) + return false; + + /* + * Since mmu_lock is held in read mode, it's possible another task has + * already modified the SPTE. Zap the SPTE if and only if the SPTE + * points at the SP's page table, as checking shadow-present isn't + * sufficient, e.g. the SPTE could be replaced by a leaf SPTE, or even + * another SP. Note, spte_to_child_pt() also checks that the SPTE is + * shadow-present, i.e. guards against zapping a frozen SPTE. + */ + if ((tdp_ptep_t)sp->spt != spte_to_child_pt(iter.old_spte, iter.level)) + return false; + + /* + * If a different task modified the SPTE, then it should be impossible + * for the SPTE to still be used for the to-be-zapped SP. Non-leaf + * SPTEs don't have Dirty bits, KVM always sets the Accessed bit when + * creating non-leaf SPTEs, and all other bits are immutable for non- + * leaf SPTEs, i.e. the only legal operations for non-leaf SPTEs are + * zapping and replacement. + */ + if (tdp_mmu_set_spte_atomic(kvm, &iter, SHADOW_NONPRESENT_VALUE)) { + WARN_ON_ONCE((tdp_ptep_t)sp->spt == spte_to_child_pt(iter.old_spte, iter.level)); + return false; + } + + return true; +} + +/* + * If can_yield is true, will release the MMU lock and reschedule if the + * scheduler needs the CPU or there is contention on the MMU lock. If this + * function cannot yield, it will not release the MMU lock or reschedule and + * the caller must ensure it does not supply too large a GFN range, or the + * operation can cause a soft lockup. + */ +static bool tdp_mmu_zap_leafs(struct kvm *kvm, struct kvm_mmu_page *root, + gfn_t start, gfn_t end, bool can_yield, bool flush) +{ + struct tdp_iter iter; + + end = min(end, tdp_mmu_max_gfn_exclusive()); + + lockdep_assert_held_write(&kvm->mmu_lock); + + rcu_read_lock(); + + for_each_tdp_pte_min_level(iter, kvm, root, PG_LEVEL_4K, start, end) { + if (can_yield && + tdp_mmu_iter_cond_resched(kvm, &iter, flush, false)) { + flush = false; + continue; + } + + if (!is_shadow_present_pte(iter.old_spte) || + !is_last_spte(iter.old_spte, iter.level)) + continue; + + tdp_mmu_iter_set_spte(kvm, &iter, SHADOW_NONPRESENT_VALUE); + + /* + * Zappings SPTEs in invalid roots doesn't require a TLB flush, + * see kvm_tdp_mmu_zap_invalidated_roots() for details. + */ + if (!root->role.invalid) + flush = true; + } + + rcu_read_unlock(); + + /* + * Because this flow zaps _only_ leaf SPTEs, the caller doesn't need + * to provide RCU protection as no 'struct kvm_mmu_page' will be freed. + */ + return flush; +} + +/* + * Zap leaf SPTEs for the range of gfns, [start, end), for all *VALID** roots. + * Returns true if a TLB flush is needed before releasing the MMU lock, i.e. if + * one or more SPTEs were zapped since the MMU lock was last acquired. + */ +bool kvm_tdp_mmu_zap_leafs(struct kvm *kvm, gfn_t start, gfn_t end, bool flush) +{ + struct kvm_mmu_page *root; + + lockdep_assert_held_write(&kvm->mmu_lock); + for_each_valid_tdp_mmu_root_yield_safe(kvm, root, -1) + flush = tdp_mmu_zap_leafs(kvm, root, start, end, true, flush); + + return flush; +} + +void kvm_tdp_mmu_zap_all(struct kvm *kvm) +{ + struct kvm_mmu_page *root; + + /* + * Zap all direct roots, including invalid direct roots, as all direct + * SPTEs must be dropped before returning to the caller. For TDX, mirror + * roots don't need handling in response to the mmu notifier (the caller). + * + * Zap directly even if the root is also being zapped by a concurrent + * "fast zap". Walking zapped top-level SPTEs isn't all that expensive + * and mmu_lock is already held, which means the other thread has yielded. + * + * A TLB flush is unnecessary, KVM zaps everything if and only the VM + * is being destroyed or the userspace VMM has exited. In both cases, + * KVM_RUN is unreachable, i.e. no vCPUs will ever service the request. + */ + lockdep_assert_held_write(&kvm->mmu_lock); + __for_each_tdp_mmu_root_yield_safe(kvm, root, -1, + KVM_DIRECT_ROOTS | KVM_INVALID_ROOTS) + tdp_mmu_zap_root(kvm, root, false); +} + +/* + * Zap all invalidated roots to ensure all SPTEs are dropped before the "fast + * zap" completes. + */ +void kvm_tdp_mmu_zap_invalidated_roots(struct kvm *kvm, bool shared) +{ + struct kvm_mmu_page *root; + + if (shared) + read_lock(&kvm->mmu_lock); + else + write_lock(&kvm->mmu_lock); + + for_each_tdp_mmu_root_yield_safe(kvm, root) { + if (!root->tdp_mmu_scheduled_root_to_zap) + continue; + + root->tdp_mmu_scheduled_root_to_zap = false; + KVM_BUG_ON(!root->role.invalid, kvm); + + /* + * A TLB flush is not necessary as KVM performs a local TLB + * flush when allocating a new root (see kvm_mmu_load()), and + * when migrating a vCPU to a different pCPU. Note, the local + * TLB flush on reuse also invalidates paging-structure-cache + * entries, i.e. TLB entries for intermediate paging structures, + * that may be zapped, as such entries are associated with the + * ASID on both VMX and SVM. + */ + tdp_mmu_zap_root(kvm, root, shared); + + /* + * The referenced needs to be put *after* zapping the root, as + * the root must be reachable by mmu_notifiers while it's being + * zapped + */ + kvm_tdp_mmu_put_root(kvm, root); + } + + if (shared) + read_unlock(&kvm->mmu_lock); + else + write_unlock(&kvm->mmu_lock); +} + +/* + * Mark each TDP MMU root as invalid to prevent vCPUs from reusing a root that + * is about to be zapped, e.g. in response to a memslots update. The actual + * zapping is done separately so that it happens with mmu_lock with read, + * whereas invalidating roots must be done with mmu_lock held for write (unless + * the VM is being destroyed). + * + * Note, kvm_tdp_mmu_zap_invalidated_roots() is gifted the TDP MMU's reference. + * See kvm_tdp_mmu_alloc_root(). + */ +void kvm_tdp_mmu_invalidate_roots(struct kvm *kvm, + enum kvm_tdp_mmu_root_types root_types) +{ + struct kvm_mmu_page *root; + + /* + * Invalidating invalid roots doesn't make sense, prevent developers from + * having to think about it. + */ + if (WARN_ON_ONCE(root_types & KVM_INVALID_ROOTS)) + root_types &= ~KVM_INVALID_ROOTS; + + /* + * mmu_lock must be held for write to ensure that a root doesn't become + * invalid while there are active readers (invalidating a root while + * there are active readers may or may not be problematic in practice, + * but it's uncharted territory and not supported). + * + * Waive the assertion if there are no users of @kvm, i.e. the VM is + * being destroyed after all references have been put, or if no vCPUs + * have been created (which means there are no roots), i.e. the VM is + * being destroyed in an error path of KVM_CREATE_VM. + */ + if (IS_ENABLED(CONFIG_PROVE_LOCKING) && + refcount_read(&kvm->users_count) && kvm->created_vcpus) + lockdep_assert_held_write(&kvm->mmu_lock); + + /* + * As above, mmu_lock isn't held when destroying the VM! There can't + * be other references to @kvm, i.e. nothing else can invalidate roots + * or get/put references to roots. + */ + list_for_each_entry(root, &kvm->arch.tdp_mmu_roots, link) { + if (!tdp_mmu_root_match(root, root_types)) + continue; + + /* + * Note, invalid roots can outlive a memslot update! Invalid + * roots must be *zapped* before the memslot update completes, + * but a different task can acquire a reference and keep the + * root alive after its been zapped. + */ + if (!root->role.invalid) { + root->tdp_mmu_scheduled_root_to_zap = true; + root->role.invalid = true; + } + } +} + +/* + * Installs a last-level SPTE to handle a TDP page fault. + * (NPT/EPT violation/misconfiguration) + */ +static int tdp_mmu_map_handle_target_level(struct kvm_vcpu *vcpu, + struct kvm_page_fault *fault, + struct tdp_iter *iter) +{ + struct kvm_mmu_page *sp = sptep_to_sp(rcu_dereference(iter->sptep)); + u64 new_spte; + int ret = RET_PF_FIXED; + bool wrprot = false; + + if (WARN_ON_ONCE(sp->role.level != fault->goal_level)) + return RET_PF_RETRY; + + if (is_shadow_present_pte(iter->old_spte) && + (fault->prefetch || is_access_allowed(fault, iter->old_spte)) && + is_last_spte(iter->old_spte, iter->level)) { + WARN_ON_ONCE(fault->pfn != spte_to_pfn(iter->old_spte)); + return RET_PF_SPURIOUS; + } + + if (unlikely(!fault->slot)) + new_spte = make_mmio_spte(vcpu, iter->gfn, ACC_ALL); + else + wrprot = make_spte(vcpu, sp, fault->slot, ACC_ALL, iter->gfn, + fault->pfn, iter->old_spte, fault->prefetch, + false, fault->map_writable, &new_spte); + + if (new_spte == iter->old_spte) + ret = RET_PF_SPURIOUS; + else if (tdp_mmu_set_spte_atomic(vcpu->kvm, iter, new_spte)) + return RET_PF_RETRY; + else if (is_shadow_present_pte(iter->old_spte) && + (!is_last_spte(iter->old_spte, iter->level) || + WARN_ON_ONCE(leaf_spte_change_needs_tlb_flush(iter->old_spte, new_spte)))) + kvm_flush_remote_tlbs_gfn(vcpu->kvm, iter->gfn, iter->level); + + /* + * If the page fault was caused by a write but the page is write + * protected, emulation is needed. If the emulation was skipped, + * the vCPU would have the same fault again. + */ + if (wrprot && fault->write) + ret = RET_PF_WRITE_PROTECTED; + + /* If a MMIO SPTE is installed, the MMIO will need to be emulated. */ + if (unlikely(is_mmio_spte(vcpu->kvm, new_spte))) { + vcpu->stat.pf_mmio_spte_created++; + trace_mark_mmio_spte(rcu_dereference(iter->sptep), iter->gfn, + new_spte); + ret = RET_PF_EMULATE; + } else { + trace_kvm_mmu_set_spte(iter->level, iter->gfn, + rcu_dereference(iter->sptep)); + } + + return ret; +} + +/* + * tdp_mmu_link_sp - Replace the given spte with an spte pointing to the + * provided page table. + * + * @kvm: kvm instance + * @iter: a tdp_iter instance currently on the SPTE that should be set + * @sp: The new TDP page table to install. + * @shared: This operation is running under the MMU lock in read mode. + * + * Returns: 0 if the new page table was installed. Non-0 if the page table + * could not be installed (e.g. the atomic compare-exchange failed). + */ +static int tdp_mmu_link_sp(struct kvm *kvm, struct tdp_iter *iter, + struct kvm_mmu_page *sp, bool shared) +{ + u64 spte = make_nonleaf_spte(sp->spt, !kvm_ad_enabled); + int ret = 0; + + if (shared) { + ret = tdp_mmu_set_spte_atomic(kvm, iter, spte); + if (ret) + return ret; + } else { + tdp_mmu_iter_set_spte(kvm, iter, spte); + } + + tdp_account_mmu_page(kvm, sp); + + return 0; +} + +static int tdp_mmu_split_huge_page(struct kvm *kvm, struct tdp_iter *iter, + struct kvm_mmu_page *sp, bool shared); + +/* + * Handle a TDP page fault (NPT/EPT violation/misconfiguration) by installing + * page tables and SPTEs to translate the faulting guest physical address. + */ +int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) +{ + struct kvm_mmu_page *root = tdp_mmu_get_root_for_fault(vcpu, fault); + struct kvm *kvm = vcpu->kvm; + struct tdp_iter iter; + struct kvm_mmu_page *sp; + int ret = RET_PF_RETRY; + + KVM_MMU_WARN_ON(!root || root->role.invalid); + + kvm_mmu_hugepage_adjust(vcpu, fault); + + trace_kvm_mmu_spte_requested(fault); + + rcu_read_lock(); + + for_each_tdp_pte(iter, kvm, root, fault->gfn, fault->gfn + 1) { + int r; + + if (fault->nx_huge_page_workaround_enabled) + disallowed_hugepage_adjust(fault, iter.old_spte, iter.level); + + /* + * If SPTE has been frozen by another thread, just give up and + * retry, avoiding unnecessary page table allocation and free. + */ + if (is_frozen_spte(iter.old_spte)) + goto retry; + + if (iter.level == fault->goal_level) + goto map_target_level; + + /* Step down into the lower level page table if it exists. */ + if (is_shadow_present_pte(iter.old_spte) && + !is_large_pte(iter.old_spte)) + continue; + + /* + * The SPTE is either non-present or points to a huge page that + * needs to be split. + */ + sp = tdp_mmu_alloc_sp(vcpu); + tdp_mmu_init_child_sp(sp, &iter); + if (is_mirror_sp(sp)) + kvm_mmu_alloc_external_spt(vcpu, sp); + + sp->nx_huge_page_disallowed = fault->huge_page_disallowed; + + if (is_shadow_present_pte(iter.old_spte)) { + /* Don't support large page for mirrored roots (TDX) */ + KVM_BUG_ON(is_mirror_sptep(iter.sptep), vcpu->kvm); + r = tdp_mmu_split_huge_page(kvm, &iter, sp, true); + } else { + r = tdp_mmu_link_sp(kvm, &iter, sp, true); + } + + /* + * Force the guest to retry if installing an upper level SPTE + * failed, e.g. because a different task modified the SPTE. + */ + if (r) { + tdp_mmu_free_sp(sp); + goto retry; + } + + if (fault->huge_page_disallowed && + fault->req_level >= iter.level) { + spin_lock(&kvm->arch.tdp_mmu_pages_lock); + if (sp->nx_huge_page_disallowed) + track_possible_nx_huge_page(kvm, sp, KVM_TDP_MMU); + spin_unlock(&kvm->arch.tdp_mmu_pages_lock); + } + } + + /* + * The walk aborted before reaching the target level, e.g. because the + * iterator detected an upper level SPTE was frozen during traversal. + */ + WARN_ON_ONCE(iter.level == fault->goal_level); + goto retry; + +map_target_level: + ret = tdp_mmu_map_handle_target_level(vcpu, fault, &iter); + +retry: + rcu_read_unlock(); + return ret; +} + +/* Used by mmu notifier via kvm_unmap_gfn_range() */ +bool kvm_tdp_mmu_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range, + bool flush) +{ + enum kvm_tdp_mmu_root_types types; + struct kvm_mmu_page *root; + + types = kvm_gfn_range_filter_to_root_types(kvm, range->attr_filter) | KVM_INVALID_ROOTS; + + __for_each_tdp_mmu_root_yield_safe(kvm, root, range->slot->as_id, types) + flush = tdp_mmu_zap_leafs(kvm, root, range->start, range->end, + range->may_block, flush); + + return flush; +} + +/* + * Mark the SPTEs range of GFNs [start, end) unaccessed and return non-zero + * if any of the GFNs in the range have been accessed. + * + * No need to mark the corresponding PFN as accessed as this call is coming + * from the clear_young() or clear_flush_young() notifier, which uses the + * return value to determine if the page has been accessed. + */ +static void kvm_tdp_mmu_age_spte(struct kvm *kvm, struct tdp_iter *iter) +{ + u64 new_spte; + + if (spte_ad_enabled(iter->old_spte)) { + iter->old_spte = tdp_mmu_clear_spte_bits_atomic(iter->sptep, + shadow_accessed_mask); + new_spte = iter->old_spte & ~shadow_accessed_mask; + } else { + new_spte = mark_spte_for_access_track(iter->old_spte); + /* + * It is safe for the following cmpxchg to fail. Leave the + * Accessed bit set, as the spte is most likely young anyway. + */ + if (__tdp_mmu_set_spte_atomic(kvm, iter, new_spte)) + return; + } + + trace_kvm_tdp_mmu_spte_changed(iter->as_id, iter->gfn, iter->level, + iter->old_spte, new_spte); +} + +static bool __kvm_tdp_mmu_age_gfn_range(struct kvm *kvm, + struct kvm_gfn_range *range, + bool test_only) +{ + enum kvm_tdp_mmu_root_types types; + struct kvm_mmu_page *root; + struct tdp_iter iter; + bool ret = false; + + types = kvm_gfn_range_filter_to_root_types(kvm, range->attr_filter); + + /* + * Don't support rescheduling, none of the MMU notifiers that funnel + * into this helper allow blocking; it'd be dead, wasteful code. Note, + * this helper must NOT be used to unmap GFNs, as it processes only + * valid roots! + */ + WARN_ON(types & ~KVM_VALID_ROOTS); + + guard(rcu)(); + for_each_tdp_mmu_root_rcu(kvm, root, range->slot->as_id, types) { + tdp_root_for_each_leaf_pte(iter, kvm, root, range->start, range->end) { + if (!is_accessed_spte(iter.old_spte)) + continue; + + if (test_only) + return true; + + ret = true; + kvm_tdp_mmu_age_spte(kvm, &iter); + } + } + + return ret; +} + +bool kvm_tdp_mmu_age_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range) +{ + return __kvm_tdp_mmu_age_gfn_range(kvm, range, false); +} + +bool kvm_tdp_mmu_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) +{ + return __kvm_tdp_mmu_age_gfn_range(kvm, range, true); +} + +/* + * Remove write access from all SPTEs at or above min_level that map GFNs + * [start, end). Returns true if an SPTE has been changed and the TLBs need to + * be flushed. + */ +static bool wrprot_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root, + gfn_t start, gfn_t end, int min_level) +{ + struct tdp_iter iter; + u64 new_spte; + bool spte_set = false; + + rcu_read_lock(); + + BUG_ON(min_level > KVM_MAX_HUGEPAGE_LEVEL); + + for_each_tdp_pte_min_level(iter, kvm, root, min_level, start, end) { +retry: + if (tdp_mmu_iter_cond_resched(kvm, &iter, false, true)) + continue; + + if (!is_shadow_present_pte(iter.old_spte) || + !is_last_spte(iter.old_spte, iter.level) || + !(iter.old_spte & PT_WRITABLE_MASK)) + continue; + + new_spte = iter.old_spte & ~PT_WRITABLE_MASK; + + if (tdp_mmu_set_spte_atomic(kvm, &iter, new_spte)) + goto retry; + + spte_set = true; + } + + rcu_read_unlock(); + return spte_set; +} + +/* + * Remove write access from all the SPTEs mapping GFNs in the memslot. Will + * only affect leaf SPTEs down to min_level. + * Returns true if an SPTE has been changed and the TLBs need to be flushed. + */ +bool kvm_tdp_mmu_wrprot_slot(struct kvm *kvm, + const struct kvm_memory_slot *slot, int min_level) +{ + struct kvm_mmu_page *root; + bool spte_set = false; + + lockdep_assert_held_read(&kvm->mmu_lock); + + for_each_valid_tdp_mmu_root_yield_safe(kvm, root, slot->as_id) + spte_set |= wrprot_gfn_range(kvm, root, slot->base_gfn, + slot->base_gfn + slot->npages, min_level); + + return spte_set; +} + +static struct kvm_mmu_page *tdp_mmu_alloc_sp_for_split(void) +{ + struct kvm_mmu_page *sp; + + sp = kmem_cache_zalloc(mmu_page_header_cache, GFP_KERNEL_ACCOUNT); + if (!sp) + return NULL; + + sp->spt = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT); + if (!sp->spt) { + kmem_cache_free(mmu_page_header_cache, sp); + return NULL; + } + + return sp; +} + +/* Note, the caller is responsible for initializing @sp. */ +static int tdp_mmu_split_huge_page(struct kvm *kvm, struct tdp_iter *iter, + struct kvm_mmu_page *sp, bool shared) +{ + const u64 huge_spte = iter->old_spte; + const int level = iter->level; + int ret, i; + + /* + * No need for atomics when writing to sp->spt since the page table has + * not been linked in yet and thus is not reachable from any other CPU. + */ + for (i = 0; i < SPTE_ENT_PER_PAGE; i++) + sp->spt[i] = make_small_spte(kvm, huge_spte, sp->role, i); + + /* + * Replace the huge spte with a pointer to the populated lower level + * page table. Since we are making this change without a TLB flush vCPUs + * will see a mix of the split mappings and the original huge mapping, + * depending on what's currently in their TLB. This is fine from a + * correctness standpoint since the translation will be the same either + * way. + */ + ret = tdp_mmu_link_sp(kvm, iter, sp, shared); + if (ret) + goto out; + + /* + * tdp_mmu_link_sp_atomic() will handle subtracting the huge page we + * are overwriting from the page stats. But we have to manually update + * the page stats with the new present child pages. + */ + kvm_update_page_stats(kvm, level - 1, SPTE_ENT_PER_PAGE); + +out: + trace_kvm_mmu_split_huge_page(iter->gfn, huge_spte, level, ret); + return ret; +} + +static int tdp_mmu_split_huge_pages_root(struct kvm *kvm, + struct kvm_mmu_page *root, + gfn_t start, gfn_t end, + int target_level, bool shared) +{ + struct kvm_mmu_page *sp = NULL; + struct tdp_iter iter; + + rcu_read_lock(); + + /* + * Traverse the page table splitting all huge pages above the target + * level into one lower level. For example, if we encounter a 1GB page + * we split it into 512 2MB pages. + * + * Since the TDP iterator uses a pre-order traversal, we are guaranteed + * to visit an SPTE before ever visiting its children, which means we + * will correctly recursively split huge pages that are more than one + * level above the target level (e.g. splitting a 1GB to 512 2MB pages, + * and then splitting each of those to 512 4KB pages). + */ + for_each_tdp_pte_min_level(iter, kvm, root, target_level + 1, start, end) { +retry: + if (tdp_mmu_iter_cond_resched(kvm, &iter, false, shared)) + continue; + + if (!is_shadow_present_pte(iter.old_spte) || !is_large_pte(iter.old_spte)) + continue; + + if (!sp) { + rcu_read_unlock(); + + if (shared) + read_unlock(&kvm->mmu_lock); + else + write_unlock(&kvm->mmu_lock); + + sp = tdp_mmu_alloc_sp_for_split(); + + if (shared) + read_lock(&kvm->mmu_lock); + else + write_lock(&kvm->mmu_lock); + + if (!sp) { + trace_kvm_mmu_split_huge_page(iter.gfn, + iter.old_spte, + iter.level, -ENOMEM); + return -ENOMEM; + } + + rcu_read_lock(); + + iter.yielded = true; + continue; + } + + tdp_mmu_init_child_sp(sp, &iter); + + if (tdp_mmu_split_huge_page(kvm, &iter, sp, shared)) + goto retry; + + sp = NULL; + } + + rcu_read_unlock(); + + /* + * It's possible to exit the loop having never used the last sp if, for + * example, a vCPU doing HugePage NX splitting wins the race and + * installs its own sp in place of the last sp we tried to split. + */ + if (sp) + tdp_mmu_free_sp(sp); + + return 0; +} + + +/* + * Try to split all huge pages mapped by the TDP MMU down to the target level. + */ +void kvm_tdp_mmu_try_split_huge_pages(struct kvm *kvm, + const struct kvm_memory_slot *slot, + gfn_t start, gfn_t end, + int target_level, bool shared) +{ + struct kvm_mmu_page *root; + int r = 0; + + kvm_lockdep_assert_mmu_lock_held(kvm, shared); + for_each_valid_tdp_mmu_root_yield_safe(kvm, root, slot->as_id) { + r = tdp_mmu_split_huge_pages_root(kvm, root, start, end, target_level, shared); + if (r) { + kvm_tdp_mmu_put_root(kvm, root); + break; + } + } +} + +static bool tdp_mmu_need_write_protect(struct kvm *kvm, struct kvm_mmu_page *sp) +{ + /* + * All TDP MMU shadow pages share the same role as their root, aside + * from level, so it is valid to key off any shadow page to determine if + * write protection is needed for an entire tree. + */ + return kvm_mmu_page_ad_need_write_protect(kvm, sp) || !kvm_ad_enabled; +} + +static void clear_dirty_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root, + gfn_t start, gfn_t end) +{ + const u64 dbit = tdp_mmu_need_write_protect(kvm, root) ? + PT_WRITABLE_MASK : shadow_dirty_mask; + struct tdp_iter iter; + + rcu_read_lock(); + + tdp_root_for_each_pte(iter, kvm, root, start, end) { +retry: + if (!is_shadow_present_pte(iter.old_spte) || + !is_last_spte(iter.old_spte, iter.level)) + continue; + + if (tdp_mmu_iter_cond_resched(kvm, &iter, false, true)) + continue; + + KVM_MMU_WARN_ON(dbit == shadow_dirty_mask && + spte_ad_need_write_protect(iter.old_spte)); + + if (!(iter.old_spte & dbit)) + continue; + + if (tdp_mmu_set_spte_atomic(kvm, &iter, iter.old_spte & ~dbit)) + goto retry; + } + + rcu_read_unlock(); +} + +/* + * Clear the dirty status (D-bit or W-bit) of all the SPTEs mapping GFNs in the + * memslot. + */ +void kvm_tdp_mmu_clear_dirty_slot(struct kvm *kvm, + const struct kvm_memory_slot *slot) +{ + struct kvm_mmu_page *root; + + lockdep_assert_held_read(&kvm->mmu_lock); + for_each_valid_tdp_mmu_root_yield_safe(kvm, root, slot->as_id) + clear_dirty_gfn_range(kvm, root, slot->base_gfn, + slot->base_gfn + slot->npages); +} + +static void clear_dirty_pt_masked(struct kvm *kvm, struct kvm_mmu_page *root, + gfn_t gfn, unsigned long mask, bool wrprot) +{ + const u64 dbit = (wrprot || tdp_mmu_need_write_protect(kvm, root)) ? + PT_WRITABLE_MASK : shadow_dirty_mask; + struct tdp_iter iter; + + lockdep_assert_held_write(&kvm->mmu_lock); + + rcu_read_lock(); + + tdp_root_for_each_leaf_pte(iter, kvm, root, gfn + __ffs(mask), + gfn + BITS_PER_LONG) { + if (!mask) + break; + + KVM_MMU_WARN_ON(dbit == shadow_dirty_mask && + spte_ad_need_write_protect(iter.old_spte)); + + if (iter.level > PG_LEVEL_4K || + !(mask & (1UL << (iter.gfn - gfn)))) + continue; + + mask &= ~(1UL << (iter.gfn - gfn)); + + if (!(iter.old_spte & dbit)) + continue; + + iter.old_spte = tdp_mmu_clear_spte_bits(iter.sptep, + iter.old_spte, dbit, + iter.level); + + trace_kvm_tdp_mmu_spte_changed(iter.as_id, iter.gfn, iter.level, + iter.old_spte, + iter.old_spte & ~dbit); + } + + rcu_read_unlock(); +} + +/* + * Clear the dirty status (D-bit or W-bit) of all the 4k SPTEs mapping GFNs for + * which a bit is set in mask, starting at gfn. The given memslot is expected to + * contain all the GFNs represented by set bits in the mask. + */ +void kvm_tdp_mmu_clear_dirty_pt_masked(struct kvm *kvm, + struct kvm_memory_slot *slot, + gfn_t gfn, unsigned long mask, + bool wrprot) +{ + struct kvm_mmu_page *root; + + for_each_valid_tdp_mmu_root(kvm, root, slot->as_id) + clear_dirty_pt_masked(kvm, root, gfn, mask, wrprot); +} + +static int tdp_mmu_make_huge_spte(struct kvm *kvm, + struct tdp_iter *parent, + u64 *huge_spte) +{ + struct kvm_mmu_page *root = spte_to_child_sp(parent->old_spte); + gfn_t start = parent->gfn; + gfn_t end = start + KVM_PAGES_PER_HPAGE(parent->level); + struct tdp_iter iter; + + tdp_root_for_each_leaf_pte(iter, kvm, root, start, end) { + /* + * Use the parent iterator when checking for forward progress so + * that KVM doesn't get stuck continuously trying to yield (i.e. + * returning -EAGAIN here and then failing the forward progress + * check in the caller ad nauseam). + */ + if (tdp_mmu_iter_need_resched(kvm, parent)) + return -EAGAIN; + + *huge_spte = make_huge_spte(kvm, iter.old_spte, parent->level); + return 0; + } + + return -ENOENT; +} + +static void recover_huge_pages_range(struct kvm *kvm, + struct kvm_mmu_page *root, + const struct kvm_memory_slot *slot) +{ + gfn_t start = slot->base_gfn; + gfn_t end = start + slot->npages; + struct tdp_iter iter; + int max_mapping_level; + bool flush = false; + u64 huge_spte; + int r; + + if (WARN_ON_ONCE(kvm_slot_dirty_track_enabled(slot))) + return; + + rcu_read_lock(); + + for_each_tdp_pte_min_level(iter, kvm, root, PG_LEVEL_2M, start, end) { +retry: + if (tdp_mmu_iter_cond_resched(kvm, &iter, flush, true)) { + flush = false; + continue; + } + + if (iter.level > KVM_MAX_HUGEPAGE_LEVEL || + !is_shadow_present_pte(iter.old_spte)) + continue; + + /* + * Don't zap leaf SPTEs, if a leaf SPTE could be replaced with + * a large page size, then its parent would have been zapped + * instead of stepping down. + */ + if (is_last_spte(iter.old_spte, iter.level)) + continue; + + /* + * If iter.gfn resides outside of the slot, i.e. the page for + * the current level overlaps but is not contained by the slot, + * then the SPTE can't be made huge. More importantly, trying + * to query that info from slot->arch.lpage_info will cause an + * out-of-bounds access. + */ + if (iter.gfn < start || iter.gfn >= end) + continue; + + max_mapping_level = kvm_mmu_max_mapping_level(kvm, NULL, slot, iter.gfn); + if (max_mapping_level < iter.level) + continue; + + r = tdp_mmu_make_huge_spte(kvm, &iter, &huge_spte); + if (r == -EAGAIN) + goto retry; + else if (r) + continue; + + if (tdp_mmu_set_spte_atomic(kvm, &iter, huge_spte)) + goto retry; + + flush = true; + } + + if (flush) + kvm_flush_remote_tlbs_memslot(kvm, slot); + + rcu_read_unlock(); +} + +/* + * Recover huge page mappings within the slot by replacing non-leaf SPTEs with + * huge SPTEs where possible. + */ +void kvm_tdp_mmu_recover_huge_pages(struct kvm *kvm, + const struct kvm_memory_slot *slot) +{ + struct kvm_mmu_page *root; + + lockdep_assert_held_read(&kvm->mmu_lock); + for_each_valid_tdp_mmu_root_yield_safe(kvm, root, slot->as_id) + recover_huge_pages_range(kvm, root, slot); +} + +/* + * Removes write access on the last level SPTE mapping this GFN and unsets the + * MMU-writable bit to ensure future writes continue to be intercepted. + * Returns true if an SPTE was set and a TLB flush is needed. + */ +static bool write_protect_gfn(struct kvm *kvm, struct kvm_mmu_page *root, + gfn_t gfn, int min_level) +{ + struct tdp_iter iter; + u64 new_spte; + bool spte_set = false; + + BUG_ON(min_level > KVM_MAX_HUGEPAGE_LEVEL); + + rcu_read_lock(); + + for_each_tdp_pte_min_level(iter, kvm, root, min_level, gfn, gfn + 1) { + if (!is_shadow_present_pte(iter.old_spte) || + !is_last_spte(iter.old_spte, iter.level)) + continue; + + new_spte = iter.old_spte & + ~(PT_WRITABLE_MASK | shadow_mmu_writable_mask); + + if (new_spte == iter.old_spte) + break; + + tdp_mmu_iter_set_spte(kvm, &iter, new_spte); + spte_set = true; + } + + rcu_read_unlock(); + + return spte_set; +} + +/* + * Removes write access on the last level SPTE mapping this GFN and unsets the + * MMU-writable bit to ensure future writes continue to be intercepted. + * Returns true if an SPTE was set and a TLB flush is needed. + */ +bool kvm_tdp_mmu_write_protect_gfn(struct kvm *kvm, + struct kvm_memory_slot *slot, gfn_t gfn, + int min_level) +{ + struct kvm_mmu_page *root; + bool spte_set = false; + + lockdep_assert_held_write(&kvm->mmu_lock); + for_each_valid_tdp_mmu_root(kvm, root, slot->as_id) + spte_set |= write_protect_gfn(kvm, root, gfn, min_level); + + return spte_set; +} + +/* + * Return the level of the lowest level SPTE added to sptes. + * That SPTE may be non-present. + * + * Must be called between kvm_tdp_mmu_walk_lockless_{begin,end}. + */ +int kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, + int *root_level) +{ + struct kvm_mmu_page *root = root_to_sp(vcpu->arch.mmu->root.hpa); + struct tdp_iter iter; + gfn_t gfn = addr >> PAGE_SHIFT; + int leaf = -1; + + *root_level = vcpu->arch.mmu->root_role.level; + + for_each_tdp_pte(iter, vcpu->kvm, root, gfn, gfn + 1) { + leaf = iter.level; + sptes[leaf] = iter.old_spte; + } + + return leaf; +} + +/* + * Returns the last level spte pointer of the shadow page walk for the given + * gpa, and sets *spte to the spte value. This spte may be non-preset. If no + * walk could be performed, returns NULL and *spte does not contain valid data. + * + * Contract: + * - Must be called between kvm_tdp_mmu_walk_lockless_{begin,end}. + * - The returned sptep must not be used after kvm_tdp_mmu_walk_lockless_end. + * + * WARNING: This function is only intended to be called during fast_page_fault. + */ +u64 *kvm_tdp_mmu_fast_pf_get_last_sptep(struct kvm_vcpu *vcpu, gfn_t gfn, + u64 *spte) +{ + /* Fast pf is not supported for mirrored roots */ + struct kvm_mmu_page *root = tdp_mmu_get_root(vcpu, KVM_DIRECT_ROOTS); + struct tdp_iter iter; + tdp_ptep_t sptep = NULL; + + for_each_tdp_pte(iter, vcpu->kvm, root, gfn, gfn + 1) { + *spte = iter.old_spte; + sptep = iter.sptep; + } + + /* + * Perform the rcu_dereference to get the raw spte pointer value since + * we are passing it up to fast_page_fault, which is shared with the + * legacy MMU and thus does not retain the TDP MMU-specific __rcu + * annotation. + * + * This is safe since fast_page_fault obeys the contracts of this + * function as well as all TDP MMU contracts around modifying SPTEs + * outside of mmu_lock. + */ + return rcu_dereference(sptep); +} |