# Re: \[PATCH v1 2/8\] x86/xen: simplify xen\_oldmem\_pfn\_is\_ram()

- From: David Hildenbrand \<hidden\>
- Date: 2021-09-29 08:45:51 
- List: linux-mm
- Page: https://ratatoskr.run/linux-mm/2021/09/215193
- Thread: https://ratatoskr.run/xen-devel/2021/09/215167/t.md

```text
>
> How about
>
>      return a.mem_type != HVMMEM_mmio_dm;
>

Ha, how could I have missed that :)

>
> Result should be promoted to int and this has added benefit of not requiring changes in patch 4.
>

Can we go one step further and do


@@ -20,24 +20,11 @@ static int xen_oldmem_pfn_is_ram(unsigned long pfn)
        struct xen_hvm_get_mem_type a = {
                .domid = DOMID_SELF,
                .pfn = pfn,
+               .mem_type = HVMMEM_ram_rw,
        };
-       int ram;
 
-       if (HYPERVISOR_hvm_op(HVMOP_get_mem_type, &a))
-               return -ENXIO;
-
-       switch (a.mem_type) {
-       case HVMMEM_mmio_dm:
-               ram = 0;
-               break;
-       case HVMMEM_ram_rw:
-       case HVMMEM_ram_ro:
-       default:
-               ram = 1;
-               break;
-       }
-
-       return ram;
+       HYPERVISOR_hvm_op(HVMOP_get_mem_type, &a);
+       return a.mem_type != HVMMEM_mmio_dm;
 }
 #endif


Assuming that if HYPERVISOR_hvm_op() fails that
.mem_type is not set to HVMMEM_mmio_dm.

-- 
Thanks,

David / dhildenb


```