[RFC PATCH 5/9] kvm_main.c: split __kvm_set_memory_region logic in kvm_check_mem and kvm_prepare_batch

[Emanuele Giuseppe Esposito]

Just a function split. No functional change intended,
except for the fact that kvm_prepare_batch() does not
immediately call kvm_set_memslot() if batch->change is
KVM_MR_DELETE, but delegates the caller (__kvm_set_memory_region).

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@xxxxxxxxxx>
---
 virt/kvm/kvm_main.c | 120 +++++++++++++++++++++++++++++---------------
 1 file changed, 79 insertions(+), 41 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 17f07546d591..9d917af30593 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1927,19 +1927,9 @@ static bool kvm_check_memslot_overlap(struct kvm_memslots *slots, int id,
 	return false;
 }
 
-/*
- * Allocate some memory and give it an address in the guest physical address
- * space.
- *
- * Discontiguous memory is allowed, mostly for framebuffers.
- * This function takes also care of initializing batch->new/old/invalid/change
- * fields.
- *
- * Must be called holding kvm->slots_lock for write.
- */
-int __kvm_set_memory_region(struct kvm *kvm,
-			    const struct kvm_userspace_memory_region *mem,
-			    struct kvm_internal_memory_region_list *batch)
+static int kvm_prepare_batch(struct kvm *kvm,
+			     const struct kvm_userspace_memory_region *mem,
+			     struct kvm_internal_memory_region_list *batch)
 {
 	struct kvm_memory_slot *old, *new;
 	struct kvm_memslots *slots;
@@ -1947,34 +1937,10 @@ int __kvm_set_memory_region(struct kvm *kvm,
 	unsigned long npages;
 	gfn_t base_gfn;
 	int as_id, id;
-	int r;
-
-	r = check_memory_region_flags(mem);
-	if (r)
-		return r;
 
 	as_id = mem->slot >> 16;
 	id = (u16)mem->slot;
 
-	/* General sanity checks */
-	if ((mem->memory_size & (PAGE_SIZE - 1)) ||
-	    (mem->memory_size != (unsigned long)mem->memory_size))
-		return -EINVAL;
-	if (mem->guest_phys_addr & (PAGE_SIZE - 1))
-		return -EINVAL;
-	/* We can read the guest memory with __xxx_user() later on. */
-	if ((mem->userspace_addr & (PAGE_SIZE - 1)) ||
-	    (mem->userspace_addr != untagged_addr(mem->userspace_addr)) ||
-	     !access_ok((void __user *)(unsigned long)mem->userspace_addr,
-			mem->memory_size))
-		return -EINVAL;
-	if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_MEM_SLOTS_NUM)
-		return -EINVAL;
-	if (mem->guest_phys_addr + mem->memory_size < mem->guest_phys_addr)
-		return -EINVAL;
-	if ((mem->memory_size >> PAGE_SHIFT) > KVM_MEM_MAX_NR_PAGES)
-		return -EINVAL;
-
 	slots = __kvm_memslots(kvm, as_id);
 
 	/*
@@ -1993,7 +1959,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
 
 		batch->change = KVM_MR_DELETE;
 		batch->new = NULL;
-		return kvm_set_memslot(kvm, batch);
+		return 0;
 	}
 
 	base_gfn = (mem->guest_phys_addr >> PAGE_SHIFT);
@@ -2020,7 +1986,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
 		else if (mem->flags != old->flags)
 			change = KVM_MR_FLAGS_ONLY;
 		else /* Nothing to change. */
-			return 0;
+			return 1;
 	}
 
 	if ((change == KVM_MR_CREATE || change == KVM_MR_MOVE) &&
@@ -2041,12 +2007,81 @@ int __kvm_set_memory_region(struct kvm *kvm,
 
 	batch->new = new;
 	batch->change = change;
+	return 0;
+}
+
+static int kvm_check_mem(const struct kvm_userspace_memory_region *mem)
+{
+	int as_id, id;
+
+	as_id = mem->slot >> 16;
+	id = (u16)mem->slot;
+
+	/* General sanity checks */
+	if ((mem->memory_size & (PAGE_SIZE - 1)) ||
+	    (mem->memory_size != (unsigned long)mem->memory_size))
+		return -EINVAL;
+	if (mem->guest_phys_addr & (PAGE_SIZE - 1))
+		return -EINVAL;
+	/* We can read the guest memory with __xxx_user() later on. */
+	if ((mem->userspace_addr & (PAGE_SIZE - 1)) ||
+	    (mem->userspace_addr != untagged_addr(mem->userspace_addr)) ||
+	     !access_ok((void __user *)(unsigned long)mem->userspace_addr,
+			mem->memory_size))
+		return -EINVAL;
+	if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_MEM_SLOTS_NUM)
+		return -EINVAL;
+	if (mem->guest_phys_addr + mem->memory_size < mem->guest_phys_addr)
+		return -EINVAL;
+	if ((mem->memory_size >> PAGE_SHIFT) > KVM_MEM_MAX_NR_PAGES)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int kvm_check_memory_region(struct kvm *kvm,
+				const struct kvm_userspace_memory_region *mem,
+				struct kvm_internal_memory_region_list *batch)
+{
+	int r;
+
+	r = check_memory_region_flags(mem);
+	if (r)
+		return r;
 
-	r = kvm_set_memslot(kvm, batch);
+	r = kvm_check_mem(mem);
 	if (r)
-		kfree(new);
+		return r;
+
+	r = kvm_prepare_batch(kvm, mem, batch);
+	if (r && batch->new)
+		kfree(batch->new);
+
 	return r;
 }
+
+/*
+ * Allocate some memory and give it an address in the guest physical address
+ * space.
+ *
+ * Discontiguous memory is allowed, mostly for framebuffers.
+ * This function takes also care of initializing batch->new/old/invalid/change
+ * fields.
+ *
+ * Must be called holding kvm->slots_lock for write.
+ */
+int __kvm_set_memory_region(struct kvm *kvm,
+			    const struct kvm_userspace_memory_region *mem,
+			    struct kvm_internal_memory_region_list *batch)
+{
+	int r;
+
+	r = kvm_check_memory_region(kvm, mem, batch);
+	if (r)
+		return r;
+
+	return kvm_set_memslot(kvm, batch);
+}
 EXPORT_SYMBOL_GPL(__kvm_set_memory_region);
 
 static int kvm_set_memory_region(struct kvm *kvm,
@@ -2061,6 +2096,9 @@ static int kvm_set_memory_region(struct kvm *kvm,
 	mutex_lock(&kvm->slots_lock);
 	r = __kvm_set_memory_region(kvm, mem, batch);
 	mutex_unlock(&kvm->slots_lock);
+	/* r == 1 means empty request, nothing to do but no error */
+	if (r == 1)
+		r = 0;
 	return r;
 }
 
-- 
2.31.1