[PATCH v2 05/12] KVM: MMU: introduce vcpu_adjust_access

[Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx>]

Introduce it to split the code of adjusting pte_access from the large
function of set_spte

Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx>
---
 arch/x86/kvm/mmu.c |   63 +++++++++++++++++++++++++++++++++-------------------
 1 files changed, 40 insertions(+), 23 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index af8bcb2..43b7e0c 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2324,25 +2324,18 @@ static int mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn,
 	return 0;
 }

-static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
-		    unsigned pte_access, int level,
-		    gfn_t gfn, pfn_t pfn, bool speculative,
-		    bool can_unsync, bool host_writable)
+/*
+ * Return -1 if a race condition is detected, 1 if @gfn need to be
+ * write-protected, otherwise 0 is returned.
+ */
+static int vcpu_adjust_access(struct kvm_vcpu *vcpu, u64 *sptep,
+			      unsigned *pte_access, int level, gfn_t gfn,
+			      bool can_unsync, bool host_writable)
 {
-	u64 spte;
-	int ret = 0;
-
-	if (set_mmio_spte(sptep, gfn, pfn, pte_access))
-		return 0;
+	if (!host_writable)
+		*pte_access &= ~ACC_WRITE_MASK;

-	spte = PT_PRESENT_MASK;
-
-	if (host_writable)
-		spte |= SPTE_HOST_WRITEABLE;
-	else
-		pte_access &= ~ACC_WRITE_MASK;
-
-	if (pte_access & ACC_WRITE_MASK) {
+	if (*pte_access & ACC_WRITE_MASK) {
 		/*
 		 * Other vcpu creates new sp in the window between
 		 * mapping_level() and acquiring mmu-lock. We can
@@ -2351,7 +2344,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 		 */
 		if (level > PT_PAGE_TABLE_LEVEL &&
 		      has_wrprotected_page(vcpu->kvm, gfn, level))
-			goto done;
+			return -1;

 		/*
 		 * Optimization: for pte sync, if spte was writable the hash
@@ -2360,17 +2353,41 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 		 * Same reasoning can be applied to dirty page accounting.
 		 */
 		if (!can_unsync && is_writable_pte(*sptep))
-			goto out_access_adjust;
+			return 0;

 		if (mmu_need_write_protect(vcpu, gfn, can_unsync)) {
 			pgprintk("%s: found shadow page for %llx, marking ro\n",
 				 __func__, gfn);
-			ret = 1;
-			pte_access &= ~ACC_WRITE_MASK;
+
+			*pte_access &= ~ACC_WRITE_MASK;
+			return 1;
 		}
 	}

-out_access_adjust:
+	return 0;
+}
+
+static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
+		    unsigned pte_access, int level,
+		    gfn_t gfn, pfn_t pfn, bool speculative,
+		    bool can_unsync, bool host_writable)
+{
+	u64 spte;
+	int ret;
+
+	if (set_mmio_spte(sptep, gfn, pfn, pte_access))
+		return 0;
+
+	ret = vcpu_adjust_access(vcpu, sptep, &pte_access, level, gfn,
+				 can_unsync, host_writable);
+	if (ret < 0)
+		return 0;
+
+	spte = PT_PRESENT_MASK;
+
+	if (host_writable)
+		spte |= SPTE_HOST_WRITEABLE;
+
 	if (!speculative)
 		spte |= shadow_accessed_mask;

@@ -2399,7 +2416,7 @@ out_access_adjust:

 	if (mmu_spte_update(sptep, spte))
 		kvm_flush_remote_tlbs(vcpu->kvm);
-done:
+
 	return ret;
 }

-- 
1.7.7.6

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