KVM: Drop kvm_arch_create_memslot()

Remove kvm_arch_create_memslot() now that all arch implementations are
effectively nops.  Removing kvm_arch_create_memslot() eliminates the
possibility for arch specific code to allocate memory prior to setting
a memslot, which sets the stage for simplifying kvm_free_memslot().

Cc: Janosch Frank <frankja@linux.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/mips/kvm/mips.c

@@ -188,12 +188,6 @@ long kvm_arch_dev_ioctl(struct file *filp, unsigned int ioctl,
 	return -ENOIOCTLCMD;
 }
 
-int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
-			    unsigned long npages)
-{
-	return 0;
-}
-
 void kvm_arch_flush_shadow_all(struct kvm *kvm)
 {
 	/* Flush whole GPA */

arch/powerpc/kvm/powerpc.c

@@ -691,12 +691,6 @@ void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *free,
 	kvmppc_core_free_memslot(kvm, free, dont);
 }
 
-int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
-			    unsigned long npages)
-{
-	return 0;
-}
-
 int kvm_arch_prepare_memory_region(struct kvm *kvm,
 				   struct kvm_memory_slot *memslot,
 				   const struct kvm_userspace_memory_region *mem,

arch/s390/kvm/kvm-s390.c

@@ -4507,12 +4507,6 @@ vm_fault_t kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf)
 	return VM_FAULT_SIGBUS;
 }
 
-int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
-			    unsigned long npages)
-{
-	return 0;
-}
-
 /* Section: memory related */
 int kvm_arch_prepare_memory_region(struct kvm *kvm,
 				   struct kvm_memory_slot *memslot,

arch/x86/kvm/x86.c

@@ -9873,12 +9873,6 @@ void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *free,
 	kvm_page_track_free_memslot(free, dont);
 }
 
-int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
-			    unsigned long npages)
-{
-	return 0;
-}
-
 static int kvm_alloc_memslot_metadata(struct kvm_memory_slot *slot,
 				      unsigned long npages)
 {

include/linux/kvm_host.h

@@ -671,8 +671,6 @@ int __kvm_set_memory_region(struct kvm *kvm,
 			    const struct kvm_userspace_memory_region *mem);
 void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *free,
 			   struct kvm_memory_slot *dont);
-int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
-			    unsigned long npages);
 void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen);
 int kvm_arch_prepare_memory_region(struct kvm *kvm,
 				struct kvm_memory_slot *memslot,

virt/kvm/arm/mmu.c

@@ -2354,12 +2354,6 @@ void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *free,
 {
 }
 
-int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
-			    unsigned long npages)
-{
-	return 0;
-}
-
 void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen)
 {
 }

virt/kvm/kvm_main.c

@@ -1040,12 +1040,13 @@ int __kvm_set_memory_region(struct kvm *kvm,
 	new.base_gfn = base_gfn;
 	new.npages = npages;
 	new.flags = mem->flags;
+	new.userspace_addr = mem->userspace_addr;
 
 	if (npages) {
 		if (!old.npages)
 			change = KVM_MR_CREATE;
 		else { /* Modify an existing slot. */
-			if ((mem->userspace_addr != old.userspace_addr) ||
+			if ((new.userspace_addr != old.userspace_addr) ||
 			    (npages != old.npages) ||
 			    ((new.flags ^ old.flags) & KVM_MEM_READONLY))
 				goto out;
@@ -1080,22 +1081,14 @@ int __kvm_set_memory_region(struct kvm *kvm,
 		}
 	}
 
-	/* Free page dirty bitmap if unneeded */
+	r = -ENOMEM;
+
+	/* Allocate/free page dirty bitmap as needed */
 	if (!(new.flags & KVM_MEM_LOG_DIRTY_PAGES))
 		new.dirty_bitmap = NULL;
-
+	else if (!new.dirty_bitmap) {
-	r = -ENOMEM;
-	if (change == KVM_MR_CREATE) {
-		new.userspace_addr = mem->userspace_addr;
-
-		if (kvm_arch_create_memslot(kvm, &new, npages))
-			goto out;
-	}
-
-	/* Allocate page dirty bitmap if needed */
-	if ((new.flags & KVM_MEM_LOG_DIRTY_PAGES) && !new.dirty_bitmap) {
 		if (kvm_create_dirty_bitmap(&new) < 0)
-			goto out_free;
+			goto out;
 	}
 
 	slots = kvzalloc(sizeof(struct kvm_memslots), GFP_KERNEL_ACCOUNT);