linux-kernel - [PATCH 5/8] KVM: MMU: optimize walking unsync shadow page

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Date:	Fri, 16 Dec 2011 18:16:53 +0800
From:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
CC:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: [PATCH 5/8] KVM: MMU: optimize walking unsync shadow page

Exactly, unysnc_children is the number of unsync sptes, we can use to
avoid unnecessary spte fetching

Signed-off-by: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
---
 arch/x86/kvm/mmu.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 9bd2084..16e0642 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1468,12 +1468,15 @@ static int __mmu_unsync_walk(struct kvm_mmu_page *sp,
 			   struct kvm_mmu_pages *pvec)
 {
 	u64 *spte;
-	int i, ret, nr_unsync_leaf = 0;
+	int i, ret, nr_unsync_leaf = 0, unysnc_children = sp->unsync_children;

 	for_each_unsync_children(sp, spte, i) {
 		struct kvm_mmu_page *child;
 		u64 ent = *spte;

+		if (!unysnc_children--)
+			break;
+
 		WARN_ON(!is_shadow_present_pte(ent) || is_large_pte(ent));

 		child = page_header(ent & PT64_BASE_ADDR_MASK);
-- 
1.7.7.4

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