KVM: MMU: fix release noslot pfn

We can not directly call kvm_release_pfn_clean to release the pfn
since we can meet noslot pfn which is used to cache mmio info into
spte

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org
Signed-off-by: Avi Kivity <avi@redhat.com>

virt/kvm/kvm_main.c

@@ -1322,9 +1322,7 @@ EXPORT_SYMBOL_GPL(kvm_release_page_clean);
 
 void kvm_release_pfn_clean(pfn_t pfn)
 {
-	WARN_ON(is_error_pfn(pfn));
-
-	if (!kvm_is_mmio_pfn(pfn))
+	if (!is_error_pfn(pfn) && !kvm_is_mmio_pfn(pfn))
 		put_page(pfn_to_page(pfn));
 }
 EXPORT_SYMBOL_GPL(kvm_release_pfn_clean);