KVM: Simply gfn_to_page()

Mapping a guest page to a host page is a common operation.  Currently,
one has first to find the memory slot where the page belongs (gfn_to_memslot),
then locate the page itself (gfn_to_page()).

This is clumsy, and also won't work well with memory aliases.  So simplify
gfn_to_page() not to require memory slot translation first, and instead do it
internally.
Signed-off-by: Avi Kivity <avi@qumranet.com>

drivers/kvm/kvm.h

@@ -443,11 +443,7 @@ void kvm_emulator_want_group7_invlpg(void);
 
 extern hpa_t bad_page_address;
 
-static inline struct page *gfn_to_page(struct kvm_memory_slot *slot, gfn_t gfn)
-{
-	return slot->phys_mem[gfn - slot->base_gfn];
-}
-
+struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn);
 struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn);
 void mark_page_dirty(struct kvm *kvm, gfn_t gfn);
 
@@ -523,12 +519,6 @@ static inline int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t gva,
 	return vcpu->mmu.page_fault(vcpu, gva, error_code);
 }
 
-static inline struct page *_gfn_to_page(struct kvm *kvm, gfn_t gfn)
-{
-	struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);
-	return (slot) ? slot->phys_mem[gfn - slot->base_gfn] : NULL;
-}
-
 static inline int is_long_mode(struct kvm_vcpu *vcpu)
 {
 #ifdef CONFIG_X86_64

drivers/kvm/kvm_main.c

@@ -420,12 +420,12 @@ static int load_pdptrs(struct kvm_vcpu *vcpu, unsigned long cr3)
 	u64 pdpte;
 	u64 *pdpt;
 	int ret;
-	struct kvm_memory_slot *memslot;
+	struct page *page;
 
 	spin_lock(&vcpu->kvm->lock);
-	memslot = gfn_to_memslot(vcpu->kvm, pdpt_gfn);
-	/* FIXME: !memslot - emulate? 0xff? */
-	pdpt = kmap_atomic(gfn_to_page(memslot, pdpt_gfn), KM_USER0);
+	page = gfn_to_page(vcpu->kvm, pdpt_gfn);
+	/* FIXME: !page - emulate? 0xff? */
+	pdpt = kmap_atomic(page, KM_USER0);
 
 	ret = 1;
 	for (i = 0; i < 4; ++i) {
@@ -861,6 +861,17 @@ struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn)
 }
 EXPORT_SYMBOL_GPL(gfn_to_memslot);
 
+struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn)
+{
+	struct kvm_memory_slot *slot;
+
+	slot = gfn_to_memslot(kvm, gfn);
+	if (!slot)
+		return NULL;
+	return slot->phys_mem[gfn - slot->base_gfn];
+}
+EXPORT_SYMBOL_GPL(gfn_to_page);
+
 void mark_page_dirty(struct kvm *kvm, gfn_t gfn)
 {
 	int i;
@@ -899,20 +910,20 @@ static int emulator_read_std(unsigned long addr,
 		unsigned offset = addr & (PAGE_SIZE-1);
 		unsigned tocopy = min(bytes, (unsigned)PAGE_SIZE - offset);
 		unsigned long pfn;
-		struct kvm_memory_slot *memslot;
-		void *page;
+		struct page *page;
+		void *page_virt;
 
 		if (gpa == UNMAPPED_GVA)
 			return X86EMUL_PROPAGATE_FAULT;
 		pfn = gpa >> PAGE_SHIFT;
-		memslot = gfn_to_memslot(vcpu->kvm, pfn);
-		if (!memslot)
+		page = gfn_to_page(vcpu->kvm, pfn);
+		if (!page)
 			return X86EMUL_UNHANDLEABLE;
-		page = kmap_atomic(gfn_to_page(memslot, pfn), KM_USER0);
+		page_virt = kmap_atomic(page, KM_USER0);
 
-		memcpy(data, page + offset, tocopy);
+		memcpy(data, page_virt + offset, tocopy);
 
-		kunmap_atomic(page, KM_USER0);
+		kunmap_atomic(page_virt, KM_USER0);
 
 		bytes -= tocopy;
 		data += tocopy;
@@ -963,16 +974,14 @@ static int emulator_read_emulated(unsigned long addr,
 static int emulator_write_phys(struct kvm_vcpu *vcpu, gpa_t gpa,
 			       unsigned long val, int bytes)
 {
-	struct kvm_memory_slot *m;
 	struct page *page;
 	void *virt;
 
 	if (((gpa + bytes - 1) >> PAGE_SHIFT) != (gpa >> PAGE_SHIFT))
 		return 0;
-	m = gfn_to_memslot(vcpu->kvm, gpa >> PAGE_SHIFT);
-	if (!m)
+	page = gfn_to_page(vcpu->kvm, gpa >> PAGE_SHIFT);
+	if (!page)
 		return 0;
-	page = gfn_to_page(m, gpa >> PAGE_SHIFT);
 	kvm_mmu_pre_write(vcpu, gpa, bytes);
 	mark_page_dirty(vcpu->kvm, gpa >> PAGE_SHIFT);
 	virt = kmap_atomic(page, KM_USER0);
@@ -2516,15 +2525,11 @@ static struct page *kvm_vm_nopage(struct vm_area_struct *vma,
 {
 	struct kvm *kvm = vma->vm_file->private_data;
 	unsigned long pgoff;
-	struct kvm_memory_slot *slot;
 	struct page *page;
 
 	*type = VM_FAULT_MINOR;
 	pgoff = ((address - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
-	slot = gfn_to_memslot(kvm, pgoff);
-	if (!slot)
-		return NOPAGE_SIGBUS;
-	page = gfn_to_page(slot, pgoff);
+	page = gfn_to_page(kvm, pgoff);
 	if (!page)
 		return NOPAGE_SIGBUS;
 	get_page(page);

drivers/kvm/mmu.c

@@ -390,13 +390,11 @@ static void rmap_write_protect(struct kvm_vcpu *vcpu, u64 gfn)
 {
 	struct kvm *kvm = vcpu->kvm;
 	struct page *page;
-	struct kvm_memory_slot *slot;
 	struct kvm_rmap_desc *desc;
 	u64 *spte;
 
-	slot = gfn_to_memslot(kvm, gfn);
-	BUG_ON(!slot);
-	page = gfn_to_page(slot, gfn);
+	page = gfn_to_page(kvm, gfn);
+	BUG_ON(!page);
 
 	while (page_private(page)) {
 		if (!(page_private(page) & 1))
@@ -711,14 +709,12 @@ hpa_t safe_gpa_to_hpa(struct kvm_vcpu *vcpu, gpa_t gpa)
 
 hpa_t gpa_to_hpa(struct kvm_vcpu *vcpu, gpa_t gpa)
 {
-	struct kvm_memory_slot *slot;
 	struct page *page;
 
 	ASSERT((gpa & HPA_ERR_MASK) == 0);
-	slot = gfn_to_memslot(vcpu->kvm, gpa >> PAGE_SHIFT);
-	if (!slot)
+	page = gfn_to_page(vcpu->kvm, gpa >> PAGE_SHIFT);
+	if (!page)
 		return gpa | HPA_ERR_MASK;
-	page = gfn_to_page(slot, gpa >> PAGE_SHIFT);
 	return ((hpa_t)page_to_pfn(page) << PAGE_SHIFT)
 		| (gpa & (PAGE_SIZE-1));
 }

drivers/kvm/vmx.c

@@ -926,9 +926,9 @@ static int init_rmode_tss(struct kvm* kvm)
 	gfn_t fn = rmode_tss_base(kvm) >> PAGE_SHIFT;
 	char *page;
 
-	p1 = _gfn_to_page(kvm, fn++);
-	p2 = _gfn_to_page(kvm, fn++);
-	p3 = _gfn_to_page(kvm, fn);
+	p1 = gfn_to_page(kvm, fn++);
+	p2 = gfn_to_page(kvm, fn++);
+	p3 = gfn_to_page(kvm, fn);
 
 	if (!p1 || !p2 || !p3) {
 		kvm_printf(kvm,"%s: gfn_to_page failed\n", __FUNCTION__);