Re: [Xen-devel] [pvops-2.6.31.12 ]Fatal DMA error! Please use 'swiotlb=force' kernel BUG at drivers/pci/xen-iommu.c:227! invalid opcode: 0000 [#1] SMP

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Thu, Mar 11, 2010 at 11:44:53AM +0100, Sander Eikelenboom wrote:
> Hi Konrad ,
> 
> On this machine i'm using
> - xen-3.4.2
> - pvops 2.6.31.6 dom0 kernel
> - debian stock 2.6.26.2-xen kernels
> - All are 64bit, total system mem is 8GB, no hardware iommu present.
> 
> I'm passing through several pci devices with great succes (worked stable for 
> several months)
> - Soundcard
> - 1 PCI and 1 PCI-e USB 2.0 cards used for videograbbing
> 
> 
> 
> Now i have tried to passthrough a third USB card, (PCI-e, USB 3.0 in this 
> case), with a new pvops 2.6.31.12 kernel.

Hmm.. That is mostly unexpected. 
> 
> But although i specified swiotlb=force, something seems to go wrong with DMA 
> mapping, dmesg from the domU shows the error below.
> The complete dmesg output is attached.
> 
> 
> [    1.139471] EXT3-fs: mounted filesystem with writeback data mode.
> [    1.275690] stty used greatest stack depth: 4472 bytes left
> [    1.532874] udevd version 125 started
> [    1.623120] usb usb1: uevent
> [    1.623154] usb 1-0:1.0: uevent
> [    2.068935] hub 1-0:1.0: state 7 ports 4 chg 0000 evt 0010
> [    2.068952] hub 1-0:1.0: port 4, status 0101, change 0001, 12 Mb/s
> [    2.172056] hub 1-0:1.0: debounce: port 4: total 100ms stable 100ms status 
> 0x101
> [    2.274050] usb 1-4: new high speed USB device using xhci_hcd and address 0
> [    2.285064] dma address needs mapping
> [    2.285081] mask: 0xffffffff
> [    2.285082]  address: [0x13654d1e0]
> [    2.285092] Fatal DMA error! Please use 'swiotlb=force'
> [    2.285115] ------------[ cut here ]------------
> [    2.285122] kernel BUG at drivers/pci/xen-iommu.c:227!

That shouldn't be there anymore. It looks like the SWIOTLB is
initialized, _but_ the other less useful IOMMU is used instead. Let me
dig in this and come back to you next week. In the internim, 2.6.32
(xen/next) should be working much better - try that.

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