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>

1 files changed, 3 insertions, 1 deletions

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 050974c051b5..1cc6e2e19982 100644
--- 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;