2 files changed, 92 insertions, 0 deletions

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 43f87ad83ff4..6f665c16e31d 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -227,6 +227,32 @@ enum {
 	READING_SHADOW_PAGE_TABLES,
 };
 
+#define KVM_UNMAPPED_PAGE	((void *) 0x500 + POISON_POINTER_DELTA)
+
+struct kvm_host_map {
+	/*
+	 * Only valid if the 'pfn' is managed by the host kernel (i.e. There is
+	 * a 'struct page' for it. When using mem= kernel parameter some memory
+	 * can be used as guest memory but they are not managed by host
+	 * kernel).
+	 * If 'pfn' is not managed by the host kernel, this field is
+	 * initialized to KVM_UNMAPPED_PAGE.
+	 */
+	struct page *page;
+	void *hva;
+	kvm_pfn_t pfn;
+	kvm_pfn_t gfn;
+};
+
+/*
+ * Used to check if the mapping is valid or not. Never use 'kvm_host_map'
+ * directly to check for that.
+ */
+static inline bool kvm_vcpu_mapped(struct kvm_host_map *map)
+{
+	return !!map->hva;
+}
+
 /*
  * Sometimes a large or cross-page mmio needs to be broken up into separate
  * exits for userspace servicing.
@@ -733,7 +759,9 @@ struct kvm_memslots *kvm_vcpu_memslots(struct kvm_vcpu *vcpu);
 struct kvm_memory_slot *kvm_vcpu_gfn_to_memslot(struct kvm_vcpu *vcpu, gfn_t gfn);
 kvm_pfn_t kvm_vcpu_gfn_to_pfn_atomic(struct kvm_vcpu *vcpu, gfn_t gfn);
 kvm_pfn_t kvm_vcpu_gfn_to_pfn(struct kvm_vcpu *vcpu, gfn_t gfn);
+int kvm_vcpu_map(struct kvm_vcpu *vcpu, gpa_t gpa, struct kvm_host_map *map);
 struct page *kvm_vcpu_gfn_to_page(struct kvm_vcpu *vcpu, gfn_t gfn);
+void kvm_vcpu_unmap(struct kvm_vcpu *vcpu, struct kvm_host_map *map, bool dirty);
 unsigned long kvm_vcpu_gfn_to_hva(struct kvm_vcpu *vcpu, gfn_t gfn);
 unsigned long kvm_vcpu_gfn_to_hva_prot(struct kvm_vcpu *vcpu, gfn_t gfn, bool *writable);
 int kvm_vcpu_read_guest_page(struct kvm_vcpu *vcpu, gfn_t gfn, void *data, int offset,
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 3194aa3d0b43..53de2f946f9e 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1742,6 +1742,70 @@ struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn)
 }
 EXPORT_SYMBOL_GPL(gfn_to_page);
 
+static int __kvm_map_gfn(struct kvm_memory_slot *slot, gfn_t gfn,
+			 struct kvm_host_map *map)
+{
+	kvm_pfn_t pfn;
+	void *hva = NULL;
+	struct page *page = KVM_UNMAPPED_PAGE;
+
+	if (!map)
+		return -EINVAL;
+
+	pfn = gfn_to_pfn_memslot(slot, gfn);
+	if (is_error_noslot_pfn(pfn))
+		return -EINVAL;
+
+	if (pfn_valid(pfn)) {
+		page = pfn_to_page(pfn);
+		hva = kmap(page);
+	} else {
+		hva = memremap(pfn_to_hpa(pfn), PAGE_SIZE, MEMREMAP_WB);
+	}
+
+	if (!hva)
+		return -EFAULT;
+
+	map->page = page;
+	map->hva = hva;
+	map->pfn = pfn;
+	map->gfn = gfn;
+
+	return 0;
+}
+
+int kvm_vcpu_map(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map)
+{
+	return __kvm_map_gfn(kvm_vcpu_gfn_to_memslot(vcpu, gfn), gfn, map);
+}
+EXPORT_SYMBOL_GPL(kvm_vcpu_map);
+
+void kvm_vcpu_unmap(struct kvm_vcpu *vcpu, struct kvm_host_map *map,
+		    bool dirty)
+{
+	if (!map)
+		return;
+
+	if (!map->hva)
+		return;
+
+	if (map->page)
+		kunmap(map->page);
+	else
+		memunmap(map->hva);
+
+	if (dirty) {
+		kvm_vcpu_mark_page_dirty(vcpu, map->gfn);
+		kvm_release_pfn_dirty(map->pfn);
+	} else {
+		kvm_release_pfn_clean(map->pfn);
+	}
+
+	map->hva = NULL;
+	map->page = NULL;
+}
+EXPORT_SYMBOL_GPL(kvm_vcpu_unmap);
+
 struct page *kvm_vcpu_gfn_to_page(struct kvm_vcpu *vcpu, gfn_t gfn)
 {
 	kvm_pfn_t pfn;