KVM: Add kernel-internal memory slots

Reserve a few memory slots for kernel internal use.  This is good for case
you have to register memory region and you want to be sure it was not
registered from userspace, and for case you want to register a memory region
that won't be seen from userspace.

Signed-off-by: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 21 insertions, 1 deletions

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 5113cbf75674..a044856bd02b 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -660,7 +660,7 @@ int kvm_set_memory_region(struct kvm *kvm,
 		goto out;
 	if (mem->guest_phys_addr & (PAGE_SIZE - 1))
 		goto out;
-	if (mem->slot >= KVM_MEMORY_SLOTS)
+	if (mem->slot >= KVM_MEMORY_SLOTS + KVM_PRIVATE_MEM_SLOTS)
 		goto out;
 	if (mem->guest_phys_addr + mem->memory_size < mem->guest_phys_addr)
 		goto out;
@@ -797,6 +797,8 @@ static int kvm_vm_ioctl_set_memory_region(struct kvm *kvm,
 					  kvm_userspace_memory_region *mem,
 					  int user_alloc)
 {
+	if (mem->slot >= KVM_MEMORY_SLOTS)
+		return -EINVAL;
 	return kvm_set_memory_region(kvm, mem, user_alloc);
 }
 
@@ -1010,6 +1012,22 @@ struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn)
 	return __gfn_to_memslot(kvm, gfn);
 }
 
+int kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn)
+{
+	int i;
+
+	gfn = unalias_gfn(kvm, gfn);
+	for (i = 0; i < KVM_MEMORY_SLOTS; ++i) {
+		struct kvm_memory_slot *memslot = &kvm->memslots[i];
+
+		if (gfn >= memslot->base_gfn
+		    && gfn < memslot->base_gfn + memslot->npages)
+			return 1;
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(kvm_is_visible_gfn);
+
 struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn)
 {
 	struct kvm_memory_slot *slot;
@@ -3087,6 +3105,8 @@ static struct page *kvm_vm_nopage(struct vm_area_struct *vma,
 	struct page *page;
 
 	pgoff = ((address - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
+	if (!kvm_is_visible_gfn(kvm, pgoff))
+		return NOPAGE_SIGBUS;
 	page = gfn_to_page(kvm, pgoff);
 	if (is_error_page(page)) {
 		kvm_release_page(page);