Re: [Xen-devel] [PATCH] x86/mm: Reduce debug overhead of __virt_to_maddr()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.08.17 at 15:58, <andrew.cooper3@xxxxxxxxxx> wrote:
> --- a/xen/include/asm-x86/x86_64/page.h
> +++ b/xen/include/asm-x86/x86_64/page.h
> @@ -51,13 +51,15 @@ extern unsigned long xen_virt_end;
>  
>  static inline unsigned long __virt_to_maddr(unsigned long va)
>  {
> -    ASSERT(va >= XEN_VIRT_START);
>      ASSERT(va < DIRECTMAP_VIRT_END);
>      if ( va >= DIRECTMAP_VIRT_START )
>          va -= DIRECTMAP_VIRT_START;
>      else
>      {
> -        ASSERT(va < XEN_VIRT_END);
> +        BUILD_BUG_ON(XEN_VIRT_END - XEN_VIRT_START != GB(1));
> +        ASSERT(((long)va >> (PAGE_ORDER_1G + PAGE_SHIFT)) ==
> +               ((long)XEN_VIRT_START >> (PAGE_ORDER_1G + PAGE_SHIFT)));

Do you really need the casts here? I.e. what's wrong here with
doing unsigned long arithmetic?

Jan


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