Re: [Xen-devel] [PATCH 5/6] xen: arm: correctly round down MFN to 1GB boundary make sure pagetable mask macros as physaddr size

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 10/10/2013 03:43 PM, Ian Campbell wrote:
> ~FIRST_MASK is nothing like correct for rounding down an MFN. It is the
> inverse *and* an address not a framenumber so wrong in every dimension! We
> cannot use FIRST_MASK since that would mask off any zeroeth level bits.
> Instead calculate the correct value from FIRST_SIZE.
>
> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
Acked-by: Julien Grall <julien.grall@xxxxxxxxxx>
> ---
>   xen/arch/arm/mm.c |    2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
> index 16bbb39..cc72e78 100644
> --- a/xen/arch/arm/mm.c
> +++ b/xen/arch/arm/mm.c
> @@ -639,7 +639,7 @@ void __init setup_xenheap_mappings(unsigned long base_mfn,
>       end_mfn = base_mfn + nr_mfns;
>
>       /* Align to previous 1GB boundary */
> -    base_mfn &= ~FIRST_MASK;
> +    base_mfn &= ~((FIRST_SIZE>>PAGE_SHIFT)-1);
>
>       offset = base_mfn - xenheap_mfn_start;
>       vaddr = DIRECTMAP_VIRT_START + offset*PAGE_SIZE;
--
Julien Grall

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