Re: [PATCH] x86/mm: use "break" in arch_memory_op()

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 19 Dec 2023, Jan Beulich wrote:
> The final return statement is unreachable and hence disliked by Misra
> C:2012 (rule 2.1). Convert those case-specific (main) return statements
> which already use "rc", or in one case when it can be used without
> further adding of code, to break.
> 
> No functional change intended.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> ---
> This is an alternative proposal to
> https://lists.xen.org/archives/html/xen-devel/2023-12/msg01537.html.
> Yet another option would be to simply pull the default case out of the
> switch() statement.
> 
> --- a/xen/arch/x86/mm.c
> +++ b/xen/arch/x86/mm.c
> @@ -4724,7 +4724,7 @@ long arch_memory_op(unsigned long cmd, X
>          spin_unlock(&d->arch.e820_lock);
>  
>          rcu_unlock_domain(d);
> -        return rc;
> +        break;
>      }
>  
>      case XENMEM_memory_map:
> @@ -4818,7 +4818,7 @@ long arch_memory_op(unsigned long cmd, X
>          if ( __copy_to_guest(arg, &ctxt.map, 1) )
>              return -EFAULT;
>  
> -        return 0;
> +        break;
>      }

There are also two other return 0; under case XENMEM_memory_map and
XENMEM_machphys_mapping. I would be consistent and either leave this
return 0 alone, or change all the return 0.

Either way, this patch is correct, so:

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


>      case XENMEM_machphys_mapping:
> @@ -4880,7 +4880,7 @@ long arch_memory_op(unsigned long cmd, X
>          }
>  
>          rcu_unlock_domain(d);
> -        return rc;
> +        break;
>      }
>  #endif
>  
> @@ -4888,7 +4888,7 @@ long arch_memory_op(unsigned long cmd, X
>          return subarch_memory_op(cmd, arg);
>      }
>  
> -    return 0;
> +    return rc;
>  }
>  
>  int cf_check mmio_ro_emulated_write(
>