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xen-devel
Re: [Xen-devel] Xen Kernel (3.0.2) breaks b44 module
>>> Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> 12.05.06 11:03 >>>
>
>On 12 May 2006, at 09:57, Jan Beulich wrote:
>
>> This ought to be attributed to the fact that B44 supports only 30-bit
>> DMA addresses (and does special checking), but
>> XenLinux doesn't have a distinct DMA zone restricted to 24-bit
>> addresses, and both dma_alloc_coherent() and swiotlb are
>> restricting physical addresses to 31 bits only (at least the former
>> could certainly look at the device's DMA mask and
>> use that value rather than hard-coding 31).
>
>If dma_alloc_coherent isn't doing that then it should be patched to do
>so. Even though it won't help right now (since Xen will reject any
>requests more restricted than 31 bits) it will be needed when Xen is
>fixed to support basket-case hardware.
I agree, but this wouldn't help this specific case, as the driver also (and
mostly) uses pci_map_single on skb->data,
which ends up in swiotlb. Since swiotlb does its allocation and range
restriction during init, adjusting things here
would likely be more complicated (or cost performance, if one wanted to further
restrict the range upon use when
needed).
Jan
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