Linux Virtualization - Sep 2021 - [PATCH v1 2/8] x86/xen: simplify xen_oldmem_pfn_is_ram()

On 9/28/21 2:22 PM, David Hildenbrand wrote:
> Let's simplify return handling.
>
> Signed-off-by: David Hildenbrand <david at redhat.com>
> ---
>  arch/x86/xen/mmu_hvm.c | 11 ++---------
>  1 file changed, 2 insertions(+), 9 deletions(-)
>
> diff --git a/arch/x86/xen/mmu_hvm.c b/arch/x86/xen/mmu_hvm.c
> index b242d1f4b426..eb61622df75b 100644
> --- a/arch/x86/xen/mmu_hvm.c
> +++ b/arch/x86/xen/mmu_hvm.c
> @@ -21,23 +21,16 @@ static int xen_oldmem_pfn_is_ram(unsigned long pfn)
>  		.domid = DOMID_SELF,
>  		.pfn = pfn,
>  	};
> -	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:
> +		return 0;
>  	default:
> -		ram = 1;
> -		break;
> +		return 1;
>  	}
> -
> -	return ram;
>  }
>  #endif
>  

How about

??? return a.mem_type != HVMMEM_mmio_dm;


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


-boris

> 
> 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