Re: [Xen-devel] [PATCH v2 1/2] page-alloc/x86: don't restrict DMA heap to node 0

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 11/08/16 11:44, Jan Beulich wrote:
> When node zero has no memory, the DMA bit width will end up getting set
> to 9, which is obviously not helpful to hold back a reasonable amount
> of low enough memory for Dom0 to use for DMA purposes. Find the lowest
> node with memory below 4Gb instead.
>
> Introduce arch_get_dma_bitsize() to keep this arch-specific logic out
> of common code.
>
> Also adjust the original calculation: I think the subtraction of 1
> should have been part of the flsl() argument rather than getting
> applied to its result. And while previously the division by 4 was valid
> to be done on the flsl() result, this now also needs to be converted,
> as is should only be applied to the spanned pages value.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> Acked-by: Julien Grall <julien.grall@xxxxxxx>
> ---
> v2: Extend commit message to reason about the calculation change. Add
>     a comment to the calculation.

Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

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