KVM: x86/mmu: WARN if TDP MMU's set_tdp_spte() sees multiple GFNs

WARN if set_tdp_spte() is invoked with multipel GFNs.  It is specifically
a callback to handle a single host PTE being changed.  Consuming the
@end parameter also eliminates the confusing 'unused' parameter.

Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210226010329.1766033-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu/tdp_mmu.c

@@ -1020,7 +1020,7 @@ int kvm_tdp_mmu_test_age_hva(struct kvm *kvm, unsigned long hva)
  * Returns non-zero if a flush is needed before releasing the MMU lock.
  */
 static int set_tdp_spte(struct kvm *kvm, struct kvm_memory_slot *slot,
-			struct kvm_mmu_page *root, gfn_t gfn, gfn_t unused,
+			struct kvm_mmu_page *root, gfn_t gfn, gfn_t end,
 			unsigned long data)
 {
 	struct tdp_iter iter;
@@ -1031,7 +1031,7 @@ static int set_tdp_spte(struct kvm *kvm, struct kvm_memory_slot *slot,
 
 	rcu_read_lock();
 
-	WARN_ON(pte_huge(*ptep));
+	WARN_ON(pte_huge(*ptep) || (gfn + 1) != end);
 
 	new_pfn = pte_pfn(*ptep);