diff options
| -rw-r--r-- | arch/x86/kvm/mmu/mmu.c | 100 | ||||
| -rw-r--r-- | arch/x86/kvm/mmu/tdp_mmu.c | 42 |
2 files changed, 98 insertions, 44 deletions
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index a9aafa88de2b..92ff15969a36 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -7596,17 +7596,43 @@ static unsigned long nx_huge_pages_to_zap(struct kvm *kvm, return ratio ? DIV_ROUND_UP(pages, ratio) : 0; } +static bool kvm_mmu_sp_dirty_logging_enabled(struct kvm *kvm, + struct kvm_mmu_page *sp) +{ + struct kvm_memory_slot *slot; + + /* + * Skip the memslot lookup if dirty tracking can't possibly be enabled, + * as memslot lookups are relatively expensive. + * + * If a memslot update is in progress, reading an incorrect value of + * kvm->nr_memslots_dirty_logging is not a problem: if it is becoming + * zero, KVM will do an unnecessary memslot lookup; if it is becoming + * nonzero, the page will be zapped unnecessarily. Either way, this + * only affects efficiency in racy situations, and not correctness. + */ + if (!atomic_read(&kvm->nr_memslots_dirty_logging)) + return false; + + slot = __gfn_to_memslot(kvm_memslots_for_spte_role(kvm, sp->role), sp->gfn); + if (WARN_ON_ONCE(!slot)) + return false; + + return kvm_slot_dirty_track_enabled(slot); +} + static void kvm_recover_nx_huge_pages(struct kvm *kvm, - enum kvm_mmu_type mmu_type) + const enum kvm_mmu_type mmu_type) { #ifdef CONFIG_X86_64 const bool is_tdp_mmu = mmu_type == KVM_TDP_MMU; + spinlock_t *tdp_mmu_pages_lock = &kvm->arch.tdp_mmu_pages_lock; #else const bool is_tdp_mmu = false; + spinlock_t *tdp_mmu_pages_lock = NULL; #endif unsigned long to_zap = nx_huge_pages_to_zap(kvm, mmu_type); struct list_head *nx_huge_pages; - struct kvm_memory_slot *slot; struct kvm_mmu_page *sp; LIST_HEAD(invalid_list); bool flush = false; @@ -7615,7 +7641,10 @@ static void kvm_recover_nx_huge_pages(struct kvm *kvm, nx_huge_pages = &kvm->arch.possible_nx_huge_pages[mmu_type].pages; rcu_idx = srcu_read_lock(&kvm->srcu); - write_lock(&kvm->mmu_lock); + if (is_tdp_mmu) + read_lock(&kvm->mmu_lock); + else + write_lock(&kvm->mmu_lock); /* * Zapping TDP MMU shadow pages, including the remote TLB flush, must @@ -7625,8 +7654,14 @@ static void kvm_recover_nx_huge_pages(struct kvm *kvm, rcu_read_lock(); for ( ; to_zap; --to_zap) { - if (list_empty(nx_huge_pages)) + if (is_tdp_mmu) + spin_lock(tdp_mmu_pages_lock); + + if (list_empty(nx_huge_pages)) { + if (is_tdp_mmu) + spin_unlock(tdp_mmu_pages_lock); break; + } /* * We use a separate list instead of just using active_mmu_pages @@ -7641,50 +7676,38 @@ static void kvm_recover_nx_huge_pages(struct kvm *kvm, WARN_ON_ONCE(!sp->nx_huge_page_disallowed); WARN_ON_ONCE(!sp->role.direct); + unaccount_nx_huge_page(kvm, sp); + + if (is_tdp_mmu) + spin_unlock(tdp_mmu_pages_lock); + /* - * Unaccount and do not attempt to recover any NX Huge Pages - * that are being dirty tracked, as they would just be faulted - * back in as 4KiB pages. The NX Huge Pages in this slot will be - * recovered, along with all the other huge pages in the slot, - * when dirty logging is disabled. - * - * Since gfn_to_memslot() is relatively expensive, it helps to - * skip it if it the test cannot possibly return true. On the - * other hand, if any memslot has logging enabled, chances are - * good that all of them do, in which case unaccount_nx_huge_page() - * is much cheaper than zapping the page. - * - * If a memslot update is in progress, reading an incorrect value - * of kvm->nr_memslots_dirty_logging is not a problem: if it is - * becoming zero, gfn_to_memslot() will be done unnecessarily; if - * it is becoming nonzero, the page will be zapped unnecessarily. - * Either way, this only affects efficiency in racy situations, - * and not correctness. + * Do not attempt to recover any NX Huge Pages that are being + * dirty tracked, as they would just be faulted back in as 4KiB + * pages. The NX Huge Pages in this slot will be recovered, + * along with all the other huge pages in the slot, when dirty + * logging is disabled. */ - slot = NULL; - if (atomic_read(&kvm->nr_memslots_dirty_logging)) { - struct kvm_memslots *slots; + if (!kvm_mmu_sp_dirty_logging_enabled(kvm, sp)) { + if (is_tdp_mmu) + flush |= kvm_tdp_mmu_zap_possible_nx_huge_page(kvm, sp); + else + kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list); - slots = kvm_memslots_for_spte_role(kvm, sp->role); - slot = __gfn_to_memslot(slots, sp->gfn); - WARN_ON_ONCE(!slot); } - if (slot && kvm_slot_dirty_track_enabled(slot)) - unaccount_nx_huge_page(kvm, sp); - else if (is_tdp_mmu) - flush |= kvm_tdp_mmu_zap_possible_nx_huge_page(kvm, sp); - else - kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list); WARN_ON_ONCE(sp->nx_huge_page_disallowed); if (need_resched() || rwlock_needbreak(&kvm->mmu_lock)) { kvm_mmu_remote_flush_or_zap(kvm, &invalid_list, flush); rcu_read_unlock(); - cond_resched_rwlock_write(&kvm->mmu_lock); - flush = false; + if (is_tdp_mmu) + cond_resched_rwlock_read(&kvm->mmu_lock); + else + cond_resched_rwlock_write(&kvm->mmu_lock); + flush = false; rcu_read_lock(); } } @@ -7692,7 +7715,10 @@ static void kvm_recover_nx_huge_pages(struct kvm *kvm, rcu_read_unlock(); - write_unlock(&kvm->mmu_lock); + if (is_tdp_mmu) + read_unlock(&kvm->mmu_lock); + else + write_unlock(&kvm->mmu_lock); srcu_read_unlock(&kvm->srcu, rcu_idx); } diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index 19907eb04a9c..31d921705dee 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -928,21 +928,49 @@ static void tdp_mmu_zap_root(struct kvm *kvm, struct kvm_mmu_page *root, bool kvm_tdp_mmu_zap_possible_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp) { - u64 old_spte; + 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; /* - * This helper intentionally doesn't allow zapping a root shadow page, - * which doesn't have a parent page table and thus no associated entry. + * 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; - old_spte = kvm_tdp_mmu_read_spte(sp->ptep); - if (WARN_ON_ONCE(!is_shadow_present_pte(old_spte))) + /* + * 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; - tdp_mmu_set_spte(kvm, kvm_mmu_page_as_id(sp), sp->ptep, old_spte, - SHADOW_NONPRESENT_VALUE, sp->gfn, sp->role.level + 1); + /* + * 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; } |