Re: [Xen-devel] [PATCH 3/3] x86/xen: use the maximum MFN to calculate the required DMA mask

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 12.11.14 at 16:25, <david.vrabel@xxxxxxxxxx> wrote:
> +u64
> +xen_swiotlb_get_required_mask(struct device *dev)
> +{
> +     u64 max_mfn;
> +
> +     max_mfn = HYPERVISOR_memory_op(XENMEM_maximum_ram_page, NULL);
> +
> +     return DMA_BIT_MASK(fls64(max_mfn << PAGE_SHIFT) + 1);
> +}

The value the hypercall returns is exclusive and an unsigned long.
Hence I'd suggest

u64
xen_swiotlb_get_required_mask(struct device *dev)
{
        unsigned long max_mfn;

        max_mfn = HYPERVISOR_memory_op(XENMEM_maximum_ram_page, NULL);

        return DMA_BIT_MASK(__fls(max_mfn - 1) + 1 + PAGE_SHIFT);
}

Jan


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