diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index cf206f68af54..bf087e91da70 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -1248,18 +1248,9 @@ struct rmap_iterator { int pos; /* index of the sptep */ }; -/* - * Iteration must be started by this function. This should also be used after - * removing/dropping sptes from the rmap link because in such cases the - * information in the iterator may not be valid. - * - * Returns sptep if found, NULL otherwise. - */ -static u64 *rmap_get_first(struct kvm_rmap_head *rmap_head, - struct rmap_iterator *iter) +static u64 *__rmap_get_first(unsigned long rmap_val, + struct rmap_iterator *iter) { - unsigned long rmap_val = kvm_rmap_get(rmap_head); - if (!rmap_val) return NULL; @@ -1273,6 +1264,19 @@ static u64 *rmap_get_first(struct kvm_rmap_head *rmap_head, return iter->desc->sptes[iter->pos]; } +/* + * Iteration must be started by this function. This should also be used after + * removing/dropping sptes from the rmap link because in such cases the + * information in the iterator may not be valid. + * + * Returns sptep if found, NULL otherwise. + */ +static u64 *rmap_get_first(struct kvm_rmap_head *rmap_head, + struct rmap_iterator *iter) +{ + return __rmap_get_first(kvm_rmap_get(rmap_head), iter); +} + /* * Must be used with a valid iterator: e.g. after rmap_get_first(). * @@ -1307,8 +1311,9 @@ static u64 *rmap_get_next(struct rmap_iterator *iter) __for_each_rmap_spte(_rmap_head_, _iter_, _sptep_) \ if (!WARN_ON_ONCE(!is_shadow_present_pte(*(_sptep_)))) \ -#define for_each_rmap_spte_lockless(_rmap_head_, _iter_, _sptep_, _spte_) \ - __for_each_rmap_spte(_rmap_head_, _iter_, _sptep_) \ +#define for_each_rmap_spte_lockless(_rmap_val_, _iter_, _sptep_, _spte_) \ + for (_sptep_ = __rmap_get_first(_rmap_val_, _iter_); \ + _sptep_; _sptep_ = rmap_get_next(_iter_)) \ if (is_shadow_present_pte(_spte_ = mmu_spte_get_lockless(sptep))) static void drop_spte(struct kvm *kvm, u64 *sptep) @@ -1734,11 +1739,11 @@ static bool kvm_rmap_age_gfn_range(struct kvm *kvm, struct kvm_rmap_head *rmap_head; struct rmap_iterator iter; unsigned long rmap_val; + u64 old_spte, new_spte; bool young = false; u64 *sptep; gfn_t gfn; int level; - u64 spte; for (level = PG_LEVEL_4K; level <= KVM_MAX_HUGEPAGE_LEVEL; level++) { for (gfn = range->start; gfn < range->end; @@ -1746,8 +1751,8 @@ static bool kvm_rmap_age_gfn_range(struct kvm *kvm, rmap_head = gfn_to_rmap(gfn, level, range->slot); rmap_val = kvm_rmap_lock_readonly(rmap_head); - for_each_rmap_spte_lockless(rmap_head, &iter, sptep, spte) { - if (!is_accessed_spte(spte)) + for_each_rmap_spte_lockless(rmap_val, &iter, sptep, old_spte) { + if (!is_accessed_spte(old_spte)) continue; if (test_only) { @@ -1755,17 +1760,18 @@ static bool kvm_rmap_age_gfn_range(struct kvm *kvm, return true; } - if (spte_ad_enabled(spte)) - clear_bit((ffs(shadow_accessed_mask) - 1), - (unsigned long *)sptep); + if (spte_ad_enabled(old_spte)) + new_spte = old_spte & ~shadow_accessed_mask; else - /* - * If the following cmpxchg fails, the - * spte is being concurrently modified - * and should most likely stay young. - */ - cmpxchg64(sptep, spte, - mark_spte_for_access_track(spte)); + new_spte = mark_spte_for_access_track(old_spte); + + /* + * Don't bother retrying if the CMPXCHG fails, + * i.e. if another CPU modified the SPTE. The + * SPTE is either being zapped or is likely + * still in-use, i.e. is still young. + */ + cmpxchg64(sptep, old_spte, new_spte); young = true; } diff --git a/arch/x86/kvm/mmu/tdp_iter.h b/arch/x86/kvm/mmu/tdp_iter.h index 364c5da6c499..f898d8d0d93c 100644 --- a/arch/x86/kvm/mmu/tdp_iter.h +++ b/arch/x86/kvm/mmu/tdp_iter.h @@ -19,6 +19,13 @@ static inline u64 kvm_tdp_mmu_read_spte(tdp_ptep_t sptep) return READ_ONCE(*rcu_dereference(sptep)); } +/* + * WARNING! mmu_lock must be held for write when using the "write atomic" or + * "clear bits atomic" APIs, otherwise KVM could overwrite the "wrong" old SPTE + * value, i.e. clobber an update from a different CPU. The only exception is + * when KVM is freezing a leaf SPTE for removal, in which case KVM doesn't care + * about the exact old SPTE value (KVM will react to the actual old value). + */ static inline u64 kvm_tdp_mmu_write_spte_atomic(tdp_ptep_t sptep, u64 new_spte) { KVM_MMU_WARN_ON(is_ept_ve_possible(new_spte)); diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index ce3f2efadb05..44dad106fad1 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -1335,19 +1335,17 @@ static void kvm_tdp_mmu_age_spte(struct kvm *kvm, struct tdp_iter *iter) if (WARN_ON_ONCE(is_mirror_sptep(iter->sptep))) return; - if (spte_ad_enabled(iter->old_spte)) { - iter->old_spte = tdp_mmu_clear_spte_bits_atomic(iter->sptep, - shadow_accessed_mask); + if (spte_ad_enabled(iter->old_spte)) new_spte = iter->old_spte & ~shadow_accessed_mask; - } else { + 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; - } + + /* + * Don't bother retrying if another CPU modified the SPTE, the SPTE is + * either being zapped or is likely still in-use, i.e. is still young. + */ + 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);