linux-kernel - [PATCH 2/8] KVM: x86/mmu: Refactor the zap loop for recovering NX lpages

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Date:   Tue, 14 Jul 2020 21:27:19 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Junaid Shahid <junaids@...gle.com>
Subject: [PATCH 2/8] KVM: x86/mmu: Refactor the zap loop for recovering NX lpages

Refactor the zap loop in kvm_recover_nx_lpages() to be a for loop that
iterates on to_zap and drop the !to_zap check that leads to the in-loop
calling of kvm_mmu_commit_zap_page().  The in-loop commit when to_zap
hits zero is superfluous now that there's an unconditional commit after
the loop to handle the case where lpage_disallowed_mmu_pages is emptied.

Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---
 arch/x86/kvm/mmu/mmu.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 48be51027af64..9cd3d2a23f8a5 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -6321,7 +6321,10 @@ static void kvm_recover_nx_lpages(struct kvm *kvm)
 
 	ratio = READ_ONCE(nx_huge_pages_recovery_ratio);
 	to_zap = ratio ? DIV_ROUND_UP(kvm->stat.nx_lpage_splits, ratio) : 0;
-	while (to_zap && !list_empty(&kvm->arch.lpage_disallowed_mmu_pages)) {
+	for ( ; to_zap; --to_zap) {
+		if (list_empty(&kvm->arch.lpage_disallowed_mmu_pages))
+			break;
+
 		/*
 		 * We use a separate list instead of just using active_mmu_pages
 		 * because the number of lpage_disallowed pages is expected to
@@ -6334,10 +6337,9 @@ static void kvm_recover_nx_lpages(struct kvm *kvm)
 		kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list);
 		WARN_ON_ONCE(sp->lpage_disallowed);
 
-		if (!--to_zap || need_resched() || spin_needbreak(&kvm->mmu_lock)) {
+		if (need_resched() || spin_needbreak(&kvm->mmu_lock)) {
 			kvm_mmu_commit_zap_page(kvm, &invalid_list);
-			if (to_zap)
-				cond_resched_lock(&kvm->mmu_lock);
+			cond_resched_lock(&kvm->mmu_lock);
 		}
 	}
 	kvm_mmu_commit_zap_page(kvm, &invalid_list);
-- 
2.26.0