diff mbox series

[10/13] KVM: x86/mmu: Allow zapping collapsible SPTEs to use MMU read lock

Message ID 20210331210841.3996155-11-bgardon@google.com (mailing list archive)
State New, archived
Headers show
Series More parallel operations for the TDP MMU | expand

Commit Message

Ben Gardon March 31, 2021, 9:08 p.m. UTC 
To speed the process of disabling dirty logging, change the TDP MMU
function which zaps collapsible SPTEs to run under the MMU read lock.

Signed-off-by: Ben Gardon <bgardon@google.com>
---
 arch/x86/kvm/mmu/mmu.c     |  9 ++++++---
 arch/x86/kvm/mmu/tdp_mmu.c | 17 +++++++++++++----
 2 files changed, 19 insertions(+), 7 deletions(-)

Comments

Paolo Bonzini April 1, 2021, 10:12 a.m. UTC | #1 
On 31/03/21 23:08, Ben Gardon wrote:
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index dcbfc784cf2f..81967b4e7d76 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -5610,10 +5610,13 @@ void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm,
>   
>   	write_lock(&kvm->mmu_lock);
>   	slot_handle_leaf(kvm, slot, kvm_mmu_zap_collapsible_spte, true);
> -
> -	if (is_tdp_mmu_enabled(kvm))
> -		kvm_tdp_mmu_zap_collapsible_sptes(kvm, slot);
>   	write_unlock(&kvm->mmu_lock);
> +
> +	if (is_tdp_mmu_enabled(kvm)) {
> +		read_lock(&kvm->mmu_lock);
> +		kvm_tdp_mmu_zap_collapsible_sptes(kvm, memslot);
> +		read_unlock(&kvm->mmu_lock);
> +	}
>   }

Same here, this will conflict with

KVM: x86/mmu: Coalesce TLB flushes when zapping collapsible SPTEs

Again, you will have to add back some "if (flush)" before the write_unlock.

Paolo
diff mbox series

Patch

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index dcbfc784cf2f..81967b4e7d76 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5610,10 +5610,13 @@  void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm,
 
 	write_lock(&kvm->mmu_lock);
 	slot_handle_leaf(kvm, slot, kvm_mmu_zap_collapsible_spte, true);
-
-	if (is_tdp_mmu_enabled(kvm))
-		kvm_tdp_mmu_zap_collapsible_sptes(kvm, slot);
 	write_unlock(&kvm->mmu_lock);
+
+	if (is_tdp_mmu_enabled(kvm)) {
+		read_lock(&kvm->mmu_lock);
+		kvm_tdp_mmu_zap_collapsible_sptes(kvm, memslot);
+		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 0e99e4675dd4..862acb868abd 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -1335,7 +1335,8 @@  static void 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, spte_set, false)) {
+retry:
+		if (tdp_mmu_iter_cond_resched(kvm, &iter, spte_set, true)) {
 			spte_set = false;
 			continue;
 		}
@@ -1350,8 +1351,14 @@  static void 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;
+		}
 		spte_set = true;
 	}
 
@@ -1370,7 +1377,9 @@  void kvm_tdp_mmu_zap_collapsible_sptes(struct kvm *kvm,
 	struct kvm_mmu_page *root;
 	int root_as_id;
 
-	for_each_tdp_mmu_root_yield_safe(kvm, root, false) {
+	lockdep_assert_held_read(&kvm->mmu_lock);
+
+	for_each_tdp_mmu_root_yield_safe(kvm, root, true) {
 		root_as_id = kvm_mmu_page_as_id(root);
 		if (root_as_id != slot->as_id)
 			continue;