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Re: [Xen-devel] swiotlb=force in Konrad's xen-pcifront-0.8.2 pvops domU

On Thu, Nov 11, 2010 at 05:02:55PM -0800, Dante Cinco wrote:
> Here's another datapoint: with iommu=1,passthrough,no-intremap,verbose
> in the Xen command line and iommu=soft in the pvops domU command line
> also results in an NMI (see below). Replacing iommu=soft with

Ok, so that enabled the VT-D and enables you to do 64-bit DMA.

> swiotlb=force in pvops domU works reliably but with the I/O
> performance degradation. It seems that regardless of whether iommu is
> enabled or disabled in the hypervisor, swiotlb=force is necessary in
> the pvops domU.

That is bizzare. I am pretty sure it should work just fine with 'iommu=soft'.
My test scripts confirm this, but let me run once more just to make sure.

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