Re: [PATCH 2.6.34] ehci-hcd: add option to enable 64-bit DMA support

[Tejun Heo]

Hello,

On 02/25/2010 12:15 PM, Yuhong Bao wrote:
>> (following thread from the ATA side) I'm with Greg on this. USB2.0 is
>> quite slow on today's standard and most 64bit machines now have IOMMU
>> of some kind anyway. 
> 
> Except that unfortunately, Intel with Lynnfield and Clarkdale decided 
> to do market segmentation on the VT-d feature. 
> This could be done because both have an integrated northbridge.
> With Lynnfield, the very common Core i5 750 CPU do not support VT-d,
> but the Core i7 800 series does.
> With Clarkdale, the very common Core i3 500 series do not support VT-d,
> but the Core i5 600 series does, except the 661.
> Not to mention that in the Core 2 generation, VT-d was available only
> on Q35/Q45/X38/X48 chipsets.

Arghhh.... I hate when intel pulls this type of 'product
differentiation' stunts.  At any rate, I'm doubtful swiotlb'ing for
usb2.0 would be noticeable at all.

Thanks.

-- 
tejun
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/