[PATCH 04/12] KVM: X86/MMU: Remove mmu_pages_clear_parents()

From: Lai Jiangshan <jiangshanlai@gmail.com>
To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Maxim Levitsky <mlevitsk@redhat.com>,
	Lai Jiangshan <jiangshan.ljs@antgroup.com>
Subject: [PATCH 04/12] KVM: X86/MMU: Remove mmu_pages_clear_parents()
Date: Sun,  5 Jun 2022 14:43:34 +0800	[thread overview]
Message-ID: <20220605064342.309219-5-jiangshanlai@gmail.com> (raw)
In-Reply-To: <20220605064342.309219-1-jiangshanlai@gmail.com>

From: Lai Jiangshan <jiangshan.ljs@antgroup.com>

mmu_unsync_walk() is designed to be workable in a pagetable which has
unsync child bits set in the shadow pages in the pagetable but without
any unsync shadow pages.

This can be resulted when the unsync shadow pages of a pagetable
can be walked from other pagetables and have been synced or zapped
when other pagetables are synced or zapped.

So mmu_pages_clear_parents() is not required even when the callers of
mmu_unsync_walk() zap or sync the pagetable.

So remove mmu_pages_clear_parents() and the child bits can be cleared in
the next call of mmu_unsync_walk() in one go.

Removing mmu_pages_clear_parents() allows for further simplifying
mmu_unsync_walk() including removing the struct mmu_page_path since
the function is the only user of it.

Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
---
 arch/x86/kvm/mmu/mmu.c | 19 -------------------
 1 file changed, 19 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index cc0207e26f6e..f35fd5c59c38 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -1948,23 +1948,6 @@ static int mmu_pages_first(struct kvm_mmu_pages *pvec,
 	return mmu_pages_next(pvec, parents, 0);
 }
 
-static void mmu_pages_clear_parents(struct mmu_page_path *parents)
-{
-	struct kvm_mmu_page *sp;
-	unsigned int level = 0;
-
-	do {
-		unsigned int idx = parents->idx[level];
-		sp = parents->parent[level];
-		if (!sp)
-			return;
-
-		WARN_ON(idx == INVALID_INDEX);
-		clear_unsync_child_bit(sp, idx);
-		level++;
-	} while (!sp->unsync_children);
-}
-
 static int mmu_sync_children(struct kvm_vcpu *vcpu,
 			     struct kvm_mmu_page *parent, bool can_yield)
 {
@@ -1989,7 +1972,6 @@ static int mmu_sync_children(struct kvm_vcpu *vcpu,
 		for_each_sp(pages, sp, parents, i) {
 			kvm_mmu_page_clear_unsync(vcpu->kvm, sp);
 			flush |= kvm_sync_page(vcpu, sp, &invalid_list) > 0;
-			mmu_pages_clear_parents(&parents);
 		}
 		if (need_resched() || rwlock_needbreak(&vcpu->kvm->mmu_lock)) {
 			kvm_mmu_remote_flush_or_zap(vcpu->kvm, &invalid_list, flush);
@@ -2298,7 +2280,6 @@ static int mmu_zap_unsync_children(struct kvm *kvm,
 
 		for_each_sp(pages, sp, parents, i) {
 			kvm_mmu_prepare_zap_page(kvm, sp, invalid_list);
-			mmu_pages_clear_parents(&parents);
 			zapped++;
 		}
 	}
-- 
2.19.1.6.gb485710b

