kvm: warn on more invariant breakage

Modifying a non-existent slot is not allowed.  Also check that the
first loop doesn't move a deleted slot beyond the used part of
the mslots array.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 050974c..1cc6e2e 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -671,6 +671,7 @@ static void update_memslots(struct kvm_memslots *slots,
 
        WARN_ON(mslots[i].id != id);
        if (!new->npages) {
+               WARN_ON(!mslots[i].npages);
                new->base_gfn = 0;
                if (mslots[i].npages)
                        slots->used_slots--;
@@ -704,7 +705,8 @@ static void update_memslots(struct kvm_memslots *slots,
                        slots->id_to_index[mslots[i].id] = i;
                        i--;
                }
-       }
+       } else
+               WARN_ON_ONCE(i != slots->used_slots);
 
        mslots[i] = *new;
        slots->id_to_index[mslots[i].id] = i;