KVM: Remove user_alloc from struct kvm_memory_slot

This field was needed to differentiate memory slots created by the new
API, KVM_SET_USER_MEMORY_REGION, from those by the old equivalent,
KVM_SET_MEMORY_REGION, whose support was dropped long before:

  commit b74a07be
  KVM: Remove kernel-allocated memory regions

Although we also have private memory slots to which KVM allocates
memory with vm_mmap(), !user_alloc slots in other words, the slot id
should be enough for differentiating them.

Note: corresponding function parameters will be removed later.
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Gleb Natapov <gleb@redhat.com>

arch/x86/kvm/x86.c

@@ -6897,32 +6897,27 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 				bool user_alloc)
 {
 	int npages = memslot->npages;
-	int map_flags = MAP_PRIVATE | MAP_ANONYMOUS;
 
-	/* Prevent internal slot pages from being moved by fork()/COW. */
-	if (memslot->id >= KVM_USER_MEM_SLOTS)
-		map_flags = MAP_SHARED | MAP_ANONYMOUS;
-
-	/*To keep backward compatibility with older userspace,
-	 *x86 needs to handle !user_alloc case.
+	/*
+	 * Only private memory slots need to be mapped here since
+	 * KVM_SET_MEMORY_REGION ioctl is no longer supported.
 	 */
-	if (!user_alloc) {
-		if (npages && !old.npages) {
+	if ((memslot->id >= KVM_USER_MEM_SLOTS) && npages && !old.npages) {
 		unsigned long userspace_addr;
 
-			userspace_addr = vm_mmap(NULL, 0,
-						 npages * PAGE_SIZE,
+		/*
+		 * MAP_SHARED to prevent internal slot pages from being moved
+		 * by fork()/COW.
+		 */
+		userspace_addr = vm_mmap(NULL, 0, npages * PAGE_SIZE,
 					 PROT_READ | PROT_WRITE,
-						 map_flags,
-						 0);
+					 MAP_SHARED | MAP_ANONYMOUS, 0);
 
 		if (IS_ERR((void *)userspace_addr))
 			return PTR_ERR((void *)userspace_addr);
 
 		memslot->userspace_addr = userspace_addr;
 	}
-	}
-
 
 	return 0;
 }
@@ -6935,7 +6930,7 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
 
 	int nr_mmu_pages = 0, npages = mem->memory_size >> PAGE_SHIFT;
 
-	if (!user_alloc && !old.user_alloc && old.npages && !npages) {
+	if ((mem->slot >= KVM_USER_MEM_SLOTS) && old.npages && !npages) {
 		int ret;
 
 		ret = vm_munmap(old.userspace_addr,

include/linux/kvm_host.h

@@ -273,7 +273,6 @@ struct kvm_memory_slot {
 	unsigned long userspace_addr;
 	u32 flags;
 	short id;
-	bool user_alloc;
 };
 
 static inline unsigned long kvm_dirty_bitmap_bytes(struct kvm_memory_slot *memslot)

virt/kvm/kvm_main.c

@@ -839,7 +839,6 @@ int __kvm_set_memory_region(struct kvm *kvm,
 
 	r = -ENOMEM;
 	if (change == KVM_MR_CREATE) {
-		new.user_alloc = user_alloc;
 		new.userspace_addr = mem->userspace_addr;
 
 		if (kvm_arch_create_memslot(&new, npages))