KVM: mmu: Refactor memslot copy

Factor out copying kvm_memslots from allocating the memory for new ones
in preparation for adding a new lock to protect the arch-specific fields
of the memslots.

No functional change intended.

Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210518173414.450044-4-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 6a6bc7a..d65be94 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1307,6 +1307,18 @@ static struct kvm_memslots *install_new_memslots(struct kvm *kvm,
        return old_memslots;
 }
 
+static size_t kvm_memslots_size(int slots)
+{
+       return sizeof(struct kvm_memslots) +
+              (sizeof(struct kvm_memory_slot) * slots);
+}
+
+static void kvm_copy_memslots(struct kvm_memslots *to,
+                             struct kvm_memslots *from)
+{
+       memcpy(to, from, kvm_memslots_size(from->used_slots));
+}
+
 /*
  * Note, at a minimum, the current number of used slots must be allocated, even
  * when deleting a memslot, as we need a complete duplicate of the memslots for
@@ -1316,19 +1328,16 @@ static struct kvm_memslots *kvm_dup_memslots(struct kvm_memslots *old,
                                             enum kvm_mr_change change)
 {
        struct kvm_memslots *slots;
-       size_t old_size, new_size;
-
-       old_size = sizeof(struct kvm_memslots) +
-                  (sizeof(struct kvm_memory_slot) * old->used_slots);
+       size_t new_size;
 
        if (change == KVM_MR_CREATE)
-               new_size = old_size + sizeof(struct kvm_memory_slot);
+               new_size = kvm_memslots_size(old->used_slots + 1);
        else
-               new_size = old_size;
+               new_size = kvm_memslots_size(old->used_slots);
 
        slots = kvzalloc(new_size, GFP_KERNEL_ACCOUNT);
        if (likely(slots))
-               memcpy(slots, old, old_size);
+               kvm_copy_memslots(slots, old);
 
        return slots;
 }