From 2db6f772b530eedcf69069e63dd7c4fdf05305fc Mon Sep 17 00:00:00 2001 From: Ben Gardon Date: Thu, 1 Apr 2021 16:37:33 -0700 Subject: [PATCH] KVM: x86/mmu: Allow zapping collapsible SPTEs to use MMU read lock To reduce the impact of disabling dirty logging, change the TDP MMU function which zaps collapsible SPTEs to run under the MMU read lock. This way, page faults on zapped SPTEs can proceed in parallel with kvm_mmu_zap_collapsible_sptes. Signed-off-by: Ben Gardon Message-Id: <20210401233736.638171-11-bgardon@google.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/mmu/mmu.c | 14 ++++++++++---- arch/x86/kvm/mmu/tdp_mmu.c | 17 +++++++++++++---- 2 files changed, 23 insertions(+), 8 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index d29aded6e4bc..2390e8a8fff1 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -5601,13 +5601,19 @@ void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm, write_lock(&kvm->mmu_lock); flush = slot_handle_leaf(kvm, slot, kvm_mmu_zap_collapsible_spte, true); - if (is_tdp_mmu_enabled(kvm)) - flush = kvm_tdp_mmu_zap_collapsible_sptes(kvm, slot, flush); - if (flush) kvm_arch_flush_remote_tlbs_memslot(kvm, slot); - write_unlock(&kvm->mmu_lock); + + if (is_tdp_mmu_enabled(kvm)) { + flush = false; + + read_lock(&kvm->mmu_lock); + flush = kvm_tdp_mmu_zap_collapsible_sptes(kvm, slot, flush); + if (flush) + kvm_arch_flush_remote_tlbs_memslot(kvm, slot); + read_unlock(&kvm->mmu_lock); + } } void kvm_arch_flush_remote_tlbs_memslot(struct kvm *kvm, diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index 2fb81033aba0..6a3b7ba4aa3c 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -1257,7 +1257,8 @@ static bool zap_collapsible_spte_range(struct kvm *kvm, rcu_read_lock(); tdp_root_for_each_pte(iter, root, start, end) { - if (tdp_mmu_iter_cond_resched(kvm, &iter, flush, false)) { +retry: + if (tdp_mmu_iter_cond_resched(kvm, &iter, flush, true)) { flush = false; continue; } @@ -1272,8 +1273,14 @@ static bool zap_collapsible_spte_range(struct kvm *kvm, pfn, PG_LEVEL_NUM)) continue; - tdp_mmu_set_spte(kvm, &iter, 0); - + if (!tdp_mmu_zap_spte_atomic(kvm, &iter)) { + /* + * The iter must explicitly re-read the SPTE because + * the atomic cmpxchg failed. + */ + iter.old_spte = READ_ONCE(*rcu_dereference(iter.sptep)); + goto retry; + } flush = true; } @@ -1292,7 +1299,9 @@ bool kvm_tdp_mmu_zap_collapsible_sptes(struct kvm *kvm, { struct kvm_mmu_page *root; - for_each_tdp_mmu_root_yield_safe(kvm, root, slot->as_id, false) + lockdep_assert_held_read(&kvm->mmu_lock); + + for_each_tdp_mmu_root_yield_safe(kvm, root, slot->as_id, true) flush = zap_collapsible_spte_range(kvm, root, slot, flush); return flush; -- 2.11.0