linux-kernel - [PATCH 1/7] KVM: MMU: correct the behavior of mmu_spte_update_no

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Date:   Wed,  3 May 2017 18:52:18 +0800
From:   guangrong.xiao@...il.com
To:     pbonzini@...hat.com, mtosatti@...hat.com, avi.kivity@...il.com,
        rkrcmar@...hat.com
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        qemu-devel@...gnu.org, Xiao Guangrong <xiaoguangrong@...cent.com>
Subject: [PATCH 1/7] KVM: MMU: correct the behavior of mmu_spte_update_no_track

From: Xiao Guangrong <xiaoguangrong@...cent.com>

Current behavior of mmu_spte_update_no_track() does not match
the name of _no_track() as actually the A/D bits are tracked
and returned to the caller

This patch introduces the real _no_track() function to update
the spte regardless of A/D bits and rename the original function
to _track()

The _no_track() function will be used by later patches to update
upper spte which need not care of A/D bits indeed

Signed-off-by: Xiao Guangrong <xiaoguangrong@...cent.com>
---
 arch/x86/kvm/mmu.c | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 5586765..ba8e7af 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -583,10 +583,29 @@ static void mmu_spte_set(u64 *sptep, u64 new_spte)
 }
 
 /*
- * Update the SPTE (excluding the PFN), but do not track changes in its
+ * Update the SPTE (excluding the PFN) regardless of accessed/dirty
+ * status which is used to update the upper level spte.
+ */
+static void mmu_spte_update_no_track(u64 *sptep, u64 new_spte)
+{
+	u64 old_spte = *sptep;
+
+	WARN_ON(!is_shadow_present_pte(new_spte));
+
+	if (!is_shadow_present_pte(old_spte)) {
+		mmu_spte_set(sptep, new_spte);
+		return;
+	}
+
+	__update_clear_spte_fast(sptep, new_spte);
+}
+
+/*
+ * Update the SPTE (excluding the PFN), the original value is
+ * returned, based on it, the caller can track changes of its
  * accessed/dirty status.
  */
-static u64 mmu_spte_update_no_track(u64 *sptep, u64 new_spte)
+static u64 mmu_spte_update_track(u64 *sptep, u64 new_spte)
 {
 	u64 old_spte = *sptep;
 
@@ -621,7 +640,7 @@ static u64 mmu_spte_update_no_track(u64 *sptep, u64 new_spte)
 static bool mmu_spte_update(u64 *sptep, u64 new_spte)
 {
 	bool flush = false;
-	u64 old_spte = mmu_spte_update_no_track(sptep, new_spte);
+	u64 old_spte = mmu_spte_update_track(sptep, new_spte);
 
 	if (!is_shadow_present_pte(old_spte))
 		return false;
-- 
2.9.3