Re: [PATCH v3 07/15] KVM: Refactor error handling for setting memory region

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On 10/25/19 1:07 AM, Sean Christopherson wrote:
Replace a big pile o' gotos with returns to make it more obvious what
error code is being returned, and to prepare for refactoring the
functional, i.e. post-checks, portion of __kvm_set_memory_region().

Reviewed-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
  virt/kvm/kvm_main.c | 40 ++++++++++++++++++----------------------
  1 file changed, 18 insertions(+), 22 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index a43902d9036d..e2f47d60f696 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -942,34 +942,33 @@ int __kvm_set_memory_region(struct kvm *kvm,
r = check_memory_region_flags(mem);
  	if (r)
-		goto out;
+		return r;
- r = -EINVAL;
  	as_id = mem->slot >> 16;
  	id = (u16)mem->slot;
/* General sanity checks */
  	if (mem->memory_size & (PAGE_SIZE - 1))
-		goto out;
+		return -EINVAL;
  	if (mem->guest_phys_addr & (PAGE_SIZE - 1))
-		goto out;
+		return -EINVAL;
  	/* We can read the guest memory with __xxx_user() later on. */
  	if ((id < KVM_USER_MEM_SLOTS) &&
  	    ((mem->userspace_addr & (PAGE_SIZE - 1)) ||
  	     !access_ok((void __user *)(unsigned long)mem->userspace_addr,
  			mem->memory_size)))
-		goto out;
+		return -EINVAL;
  	if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_MEM_SLOTS_NUM)
-		goto out;
+		return -EINVAL;
  	if (mem->guest_phys_addr + mem->memory_size < mem->guest_phys_addr)
-		goto out;
+		return -EINVAL;
slot = id_to_memslot(__kvm_memslots(kvm, as_id), id);
  	base_gfn = mem->guest_phys_addr >> PAGE_SHIFT;
  	npages = mem->memory_size >> PAGE_SHIFT;
if (npages > KVM_MEM_MAX_NR_PAGES)
-		goto out;
+		return -EINVAL;
new = old = *slot; @@ -986,20 +985,18 @@ int __kvm_set_memory_region(struct kvm *kvm,
  			if ((new.userspace_addr != old.userspace_addr) ||
  			    (npages != old.npages) ||
  			    ((new.flags ^ old.flags) & KVM_MEM_READONLY))
-				goto out;
+				return -EINVAL;
if (base_gfn != old.base_gfn)
  				change = KVM_MR_MOVE;
  			else if (new.flags != old.flags)
  				change = KVM_MR_FLAGS_ONLY;
-			else { /* Nothing to change. */
-				r = 0;
-				goto out;
-			}
+			else /* Nothing to change. */
+				return 0;
  		}
  	} else {
  		if (!old.npages)
-			goto out;
+			return -EINVAL;
change = KVM_MR_DELETE;
  		new.base_gfn = 0;
@@ -1008,29 +1005,29 @@ int __kvm_set_memory_region(struct kvm *kvm,
if ((change == KVM_MR_CREATE) || (change == KVM_MR_MOVE)) {
  		/* Check for overlaps */
-		r = -EEXIST;
  		kvm_for_each_memslot(slot, __kvm_memslots(kvm, as_id)) {
  			if (slot->id == id)
  				continue;
  			if (!((base_gfn + npages <= slot->base_gfn) ||
  			      (base_gfn >= slot->base_gfn + slot->npages)))
-				goto out;
+				return -EEXIST;
  		}
  	}
- 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) {
-		if (kvm_create_dirty_bitmap(&new) < 0)
-			goto out;
+		r = kvm_create_dirty_bitmap(&new);
+		if (r)
+			return r;

Reviewed-by: Philippe Mathieu-Daudé <f4bug@xxxxxxxxx>

  	}
slots = kvzalloc(sizeof(struct kvm_memslots), GFP_KERNEL_ACCOUNT);
-	if (!slots)
+	if (!slots) {
+		r = -ENOMEM;
  		goto out_bitmap;
+	}
  	memcpy(slots, __kvm_memslots(kvm, as_id), sizeof(struct kvm_memslots));
if ((change == KVM_MR_DELETE) || (change == KVM_MR_MOVE)) {
@@ -1081,7 +1078,6 @@ int __kvm_set_memory_region(struct kvm *kvm,
  out_bitmap:
  	if (new.dirty_bitmap && !old.dirty_bitmap)
  		kvm_destroy_dirty_bitmap(&new);
-out:
  	return r;
  }
  EXPORT_SYMBOL_GPL(__kvm_set_memory_region);

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