linux-kernel - [PATCH 5/6] KVM: MMU: delete shadow page from hash list in kvm_mmu_prepare_zap

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Date:	Wed, 13 Mar 2013 12:58:35 +0800
From:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	Gleb Natapov <gleb@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: [PATCH 5/6] KVM: MMU: delete shadow page from hash list in kvm_mmu_prepare_zap_page

Move deletion shadow page from the hash list from kvm_mmu_commit_zap_page to
kvm_mmu_prepare_zap_page, we that we can free the shadow page out of mmu-lock.

Also, delete the invalid shadow page from the hash list since this page can
not be reused anymore. This makes reset mmu-cache more easier - we do not need
to care all hash entries after reset mmu-cache

Signed-off-by: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
---
 arch/x86/kvm/mmu.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 4152766..e326099 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1469,7 +1469,7 @@ static inline void kvm_mod_used_mmu_pages(struct kvm *kvm, int nr)
 static void kvm_mmu_free_page(struct kvm_mmu_page *sp)
 {
 	ASSERT(is_empty_shadow_page(sp->spt));
-	hlist_del(&sp->hash_link);
+
 	list_del(&sp->link);
 	free_page((unsigned long)sp->spt);
 	if (!sp->role.direct)
@@ -1658,7 +1658,8 @@ static void kvm_mmu_commit_zap_page(struct kvm *kvm,

 #define for_each_gfn_indirect_valid_sp(_kvm, _sp, _gfn)			\
 	for_each_gfn_sp(_kvm, _sp, _gfn)				\
-		if ((_sp)->role.direct || (_sp)->role.invalid) {} else
+		if ((_sp)->role.direct ||				\
+		      ((_sp)->role.invalid && WARN_ON(1))) {} else

 /* @sp->gfn should be write-protected at the call site */
 static int __kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
@@ -2079,6 +2080,9 @@ static int kvm_mmu_prepare_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp,
 		unaccount_shadowed(kvm, sp->gfn);
 	if (sp->unsync)
 		kvm_unlink_unsync_page(kvm, sp);
+
+	hlist_del_init(&sp->hash_link);
+
 	if (!sp->root_count) {
 		/* Count self */
 		ret++;
-- 
1.7.7.6

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