[RFC PATCH 4/9] kvm_main.c: split logic in kvm_set_memslots

[Emanuele Giuseppe Esposito <eesposit@redhat.com>]

At this point it is also just a split, but later will handle atomic
memslot updates (thus avoiding swapping the memslot list every time).

No functional change intended.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
 virt/kvm/kvm_main.c | 37 ++++++++++++++++++++++++++++++++-----
 1 file changed, 32 insertions(+), 5 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e4fab15d0d4b..17f07546d591 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1790,12 +1790,15 @@ static void kvm_update_flags_memslot(struct kvm *kvm,
 	kvm_activate_memslot(kvm, old, new);
 }
 
-static int kvm_set_memslot(struct kvm *kvm,
-			   struct kvm_internal_memory_region_list *batch)
+/*
+ * Takes kvm->slots_arch_lock, and releases it only if
+ * invalid_slot allocation or kvm_prepare_memory_region failed.
+ */
+static int kvm_prepare_memslot(struct kvm *kvm,
+			       struct kvm_internal_memory_region_list *batch)
 {
 	struct kvm_memory_slot *invalid_slot;
 	struct kvm_memory_slot *old = batch->old;
-	struct kvm_memory_slot *new = batch->new;
 	enum kvm_mr_change change = batch->change;
 	int r;
 
@@ -1829,7 +1832,8 @@ static int kvm_set_memslot(struct kvm *kvm,
 	 * invalidation needs to be reverted.
 	 */
 	if (change == KVM_MR_DELETE || change == KVM_MR_MOVE) {
-		invalid_slot = kzalloc(sizeof(*invalid_slot), GFP_KERNEL_ACCOUNT);
+		invalid_slot = kzalloc(sizeof(*invalid_slot),
+				       GFP_KERNEL_ACCOUNT);
 		if (!invalid_slot) {
 			mutex_unlock(&kvm->slots_arch_lock);
 			return -ENOMEM;
@@ -1847,13 +1851,24 @@ static int kvm_set_memslot(struct kvm *kvm,
 		 * release slots_arch_lock.
 		 */
 		if (change == KVM_MR_DELETE || change == KVM_MR_MOVE) {
+			/* kvm_activate_memslot releases kvm->slots_arch_lock */
 			kvm_activate_memslot(kvm, invalid_slot, old);
 			kfree(invalid_slot);
 		} else {
 			mutex_unlock(&kvm->slots_arch_lock);
 		}
-		return r;
 	}
+	return r;
+}
+
+/* Must be called with kvm->slots_arch_lock held, but releases it. */
+static void kvm_finish_memslot(struct kvm *kvm,
+			       struct kvm_internal_memory_region_list *batch)
+{
+	struct kvm_memory_slot *invalid_slot = batch->invalid;
+	struct kvm_memory_slot *old = batch->old;
+	struct kvm_memory_slot *new = batch->new;
+	enum kvm_mr_change change = batch->change;
 
 	/*
 	 * For DELETE and MOVE, the working slot is now active as the INVALID
@@ -1883,6 +1898,18 @@ static int kvm_set_memslot(struct kvm *kvm,
 	 * responsible for knowing that new->arch may be stale.
 	 */
 	kvm_commit_memory_region(kvm, batch);
+}
+
+static int kvm_set_memslot(struct kvm *kvm,
+			   struct kvm_internal_memory_region_list *batch)
+{
+	int r;
+
+	r = kvm_prepare_memslot(kvm, batch);
+	if (r)
+		return r;
+
+	kvm_finish_memslot(kvm, batch);
 
 	return 0;
 }
-- 
2.31.1