There was a lot of havoc - all of the PCI BARs were useless. Is the MFN (from the pfn_to_mfn on this address) suppose to have a specific value?

For all of those setting, no_iommu=1 should do the trick. But in reality I need to double-check that:

diff --git a/arch/x86/xen/pci-swiotlb.c b/arch/x86/xen/pci-swiotlb.c index 00f2260..390f698 100644 --- a/arch/x86/xen/pci-swiotlb.c +++ b/arch/x86/xen/pci-swiotlb.c @@ -989,6 +989,8 @@ void __init xen_swiotlb_init(void) xen_swiotlb_init_with_default_size(64 * (1<<20)); /* default to 64MB */ dma_ops = &xen_swiotlb_dma_ops; iommu_detected = 1; + no_iommu = 1; /* Forces the other IOMMU (if they are detected) to + to quit, rather than initialize. */ #ifdef CONFIG_GART_IOMMU gart_iommu_aperture_disabled = 1; #endif

<sigh>I think I need to rethink this swiotlb-Xen part. This is starting to look like a hack.

Yes! That was my next step - see if it is possible to use it and if so extend it for that purpose (and without any ghastly #ifdef).