linux-kernel - [PATCH v3 2/5] KVM: MMU: clarify the logic in kvm_set_pte

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Date:	Tue, 05 Feb 2013 16:53:52 +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 v3 2/5] KVM: MMU: clarify the logic in kvm_set_pte_rmapp

In kvm_set_pte_rmapp, if the new mapping is writable, we need to remove
all spte pointing to that page otherwisewe we only need to adjust the sptes
to let them point to the new page. This patch clarifys the logic and makes
the later patch more clean

[ Impact: no logic changed ]

Signed-off-by: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
---
 arch/x86/kvm/mmu.c |   17 ++++++++---------
 1 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 68d4d5f..a0dc0d7 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1225,16 +1225,16 @@ static int kvm_set_pte_rmapp(struct kvm *kvm, unsigned long *rmapp,
 	WARN_ON(pte_huge(*ptep));
 	new_pfn = pte_pfn(*ptep);

-	for (sptep = rmap_get_first(*rmapp, &iter); sptep;) {
-		BUG_ON(!is_shadow_present_pte(*sptep));
-		rmap_printk("kvm_set_pte_rmapp: spte %p %llx\n", sptep, *sptep);
+	if (pte_write(*ptep))
+		need_flush = kvm_unmap_rmapp(kvm, rmapp, slot, data);
+	else
+		for (sptep = rmap_get_first(*rmapp, &iter); sptep;) {
+			BUG_ON(!is_shadow_present_pte(*sptep));
+			rmap_printk("kvm_set_pte_rmapp: spte %p %llx\n",
+				    sptep, *sptep);

-		need_flush = 1;
+			need_flush = 1;

-		if (pte_write(*ptep)) {
-			drop_spte(kvm, sptep);
-			sptep = rmap_get_first(*rmapp, &iter);
-		} else {
 			new_spte = *sptep & ~PT64_BASE_ADDR_MASK;
 			new_spte |= (u64)new_pfn << PAGE_SHIFT;

@@ -1246,7 +1246,6 @@ static int kvm_set_pte_rmapp(struct kvm *kvm, unsigned long *rmapp,
 			mmu_spte_set(sptep, new_spte);
 			sptep = rmap_get_next(&iter);
 		}
-	}

 	if (need_flush)
 		kvm_flush_remote_tlbs(kvm);
-- 
1.7.7.6

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