From: Sean Christopherson <seanjc@google.com>
Date: Fri, 26 Mar 2021 02:19:40 +0000 (-0700)
Subject: KVM: x86/mmu: Coalesce TDP MMU TLB flushes when zapping collapsible SPTEs
X-Git-Tag: v5.13-rc1~76^2~152
X-Git-Url: http://git.osdn.net/view?a=commitdiff_plain;h=af95b53e56e34a4df343cec32b3a3276d9d06ad3;p=tomoyo%2Ftomoyo-test1.git

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

When zapping collapsible SPTEs across multiple roots, gather pending
flushes and perform a single remote TLB flush at the end, as opposed to
flushing after processing every root.

Note, flush may be cleared by the result of zap_collapsible_spte_range().
This is intended and correct, e.g. yielding may have serviced a prior
pending flush.

Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210326021957.1424875-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---

diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index fd5000863678..31459c94290d 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -1268,21 +1268,21 @@ void kvm_tdp_mmu_clear_dirty_pt_masked(struct kvm *kvm,
  * Clear leaf entries which could be replaced by large mappings, for
  * GFNs within the slot.
  */
-static void zap_collapsible_spte_range(struct kvm *kvm,
+static bool zap_collapsible_spte_range(struct kvm *kvm,
 				       struct kvm_mmu_page *root,
-				       struct kvm_memory_slot *slot)
+				       struct kvm_memory_slot *slot,
+				       bool flush)
 {
 	gfn_t start = slot->base_gfn;
 	gfn_t end = start + slot->npages;
 	struct tdp_iter iter;
 	kvm_pfn_t pfn;
-	bool spte_set = false;
 
 	rcu_read_lock();
 
 	tdp_root_for_each_pte(iter, root, start, end) {
-		if (tdp_mmu_iter_cond_resched(kvm, &iter, spte_set)) {
-			spte_set = false;
+		if (tdp_mmu_iter_cond_resched(kvm, &iter, flush)) {
+			flush = false;
 			continue;
 		}
 
@@ -1298,12 +1298,12 @@ static void zap_collapsible_spte_range(struct kvm *kvm,
 
 		tdp_mmu_set_spte(kvm, &iter, 0);
 
-		spte_set = true;
+		flush = true;
 	}
 
 	rcu_read_unlock();
-	if (spte_set)
-		kvm_flush_remote_tlbs(kvm);
+
+	return flush;
 }
 
 /*
@@ -1314,6 +1314,7 @@ void kvm_tdp_mmu_zap_collapsible_sptes(struct kvm *kvm,
 				       struct kvm_memory_slot *slot)
 {
 	struct kvm_mmu_page *root;
+	bool flush = false;
 	int root_as_id;
 
 	for_each_tdp_mmu_root_yield_safe(kvm, root) {
@@ -1321,8 +1322,11 @@ void kvm_tdp_mmu_zap_collapsible_sptes(struct kvm *kvm,
 		if (root_as_id != slot->as_id)
 			continue;
 
-		zap_collapsible_spte_range(kvm, root, slot);
+		flush = zap_collapsible_spte_range(kvm, root, slot, flush);
 	}
+
+	if (flush)
+		kvm_flush_remote_tlbs(kvm);
 }
 
 /*