Re: [Xen-devel] [PATCH 07/24] xen/arm: mm: Clean-up mfn_to_xen_entry

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 13 Jun 2017, Julien Grall wrote:
> The physical address is computed from the machine frame number, so
> checking if the physical address is page aligned is pointless.
> 
> Furthermore, directly assigned the MFN to the corresponding field in the
> entry rather than converting to a physical address and orring the value.
> It will avoid to rely on the field position and make the code clearer.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
>  xen/arch/arm/mm.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
> index 6f63e4315a..d164ed2eda 100644
> --- a/xen/arch/arm/mm.c
> +++ b/xen/arch/arm/mm.c
> @@ -261,7 +261,6 @@ void dump_hyp_walk(vaddr_t addr)
>   */
>  static inline lpae_t mfn_to_xen_entry(unsigned long mfn, unsigned attr)
>  {
> -    paddr_t pa = ((paddr_t) mfn) << PAGE_SHIFT;
>      lpae_t e = (lpae_t) {
>          .pt = {
>              .valid = 1,           /* Mappings are present */
> @@ -316,11 +315,9 @@ static inline lpae_t mfn_to_xen_entry(unsigned long mfn, 
> unsigned attr)
>          break;
>      }
>  
> -    ASSERT(!(pa & ~PAGE_MASK));
> -    ASSERT(!(pa & ~PADDR_MASK));
> +    ASSERT(!(pfn_to_paddr(mfn) & ~PADDR_MASK));
>  
> -    /* XXX shifts */
> -    e.bits |= pa;
> +    e.pt.base = mfn;
>  
>      return e;
>  }
> -- 
> 2.11.0
> 

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