KVM: Unify kvm_mmu_pre_write() and kvm_mmu_post_write()

Instead of calling two functions and repeating expensive checks, call one
function and provide it with before/after information.
Signed-off-by: Avi Kivity <avi@qumranet.com>

drivers/kvm/kvm.h

@@ -525,8 +525,8 @@ int kvm_write_guest(struct kvm_vcpu *vcpu,
 
 unsigned long segment_base(u16 selector);
 
-void kvm_mmu_pre_write(struct kvm_vcpu *vcpu, gpa_t gpa, int bytes);
-void kvm_mmu_post_write(struct kvm_vcpu *vcpu, gpa_t gpa, int bytes);
+void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
+		       const u8 *old, const u8 *new, int bytes);
 int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva);
 void kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu);
 

drivers/kvm/kvm_main.c

@@ -1071,18 +1071,18 @@ static int emulator_write_phys(struct kvm_vcpu *vcpu, gpa_t gpa,
 {
 	struct page *page;
 	void *virt;
+	unsigned offset = offset_in_page(gpa);
 
 	if (((gpa + bytes - 1) >> PAGE_SHIFT) != (gpa >> PAGE_SHIFT))
 		return 0;
 	page = gfn_to_page(vcpu->kvm, gpa >> PAGE_SHIFT);
 	if (!page)
 		return 0;
-	kvm_mmu_pre_write(vcpu, gpa, bytes);
 	mark_page_dirty(vcpu->kvm, gpa >> PAGE_SHIFT);
 	virt = kmap_atomic(page, KM_USER0);
+	kvm_mmu_pte_write(vcpu, gpa, virt + offset, val, bytes);
 	memcpy(virt + offset_in_page(gpa), val, bytes);
 	kunmap_atomic(virt, KM_USER0);
-	kvm_mmu_post_write(vcpu, gpa, bytes);
 	return 1;
 }
 

drivers/kvm/mmu.c

@@ -1118,7 +1118,7 @@ out:
 	return r;
 }
 
-static void mmu_pre_write_zap_pte(struct kvm_vcpu *vcpu,
+static void mmu_pte_write_zap_pte(struct kvm_vcpu *vcpu,
 				  struct kvm_mmu_page *page,
 				  u64 *spte)
 {
@@ -1137,7 +1137,8 @@ static void mmu_pre_write_zap_pte(struct kvm_vcpu *vcpu,
 	*spte = 0;
 }
 
-void kvm_mmu_pre_write(struct kvm_vcpu *vcpu, gpa_t gpa, int bytes)
+void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
+		       const u8 *old, const u8 *new, int bytes)
 {
 	gfn_t gfn = gpa >> PAGE_SHIFT;
 	struct kvm_mmu_page *page;
@@ -1206,16 +1207,12 @@ void kvm_mmu_pre_write(struct kvm_vcpu *vcpu, gpa_t gpa, int bytes)
 		spte = __va(page->page_hpa);
 		spte += page_offset / sizeof(*spte);
 		while (npte--) {
-			mmu_pre_write_zap_pte(vcpu, page, spte);
+			mmu_pte_write_zap_pte(vcpu, page, spte);
 			++spte;
 		}
 	}
 }
 
-void kvm_mmu_post_write(struct kvm_vcpu *vcpu, gpa_t gpa, int bytes)
-{
-}
-
 int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva)
 {
 	gpa_t gpa = vcpu->mmu.gva_to_gpa(vcpu, gva);