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Re: [Xen-devel] pci adapter not working in dom0. works under plain Linux.

  • To: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
  • From: James Harper <james@xxxxxxxxxxxxxxxxx>
  • Date: Tue, 10 Jun 2014 11:19:18 +0000
  • Accept-language: en-AU, en-US
  • Cc: "xen-devel@xxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxx>
  • Delivery-date: Tue, 10 Jun 2014 11:19:36 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xen.org>
  • Thread-index: Ac+DCNWNPHJYbVrFQ8CYCy7O42ilYwA+kV2AACaWUvA=
  • Thread-topic: [Xen-devel] pci adapter not working in dom0. works under plain Linux.

> On Sun, Jun 08, 2014 at 11:01:25AM +0000, James Harper wrote:
> > I bought an unsupported DVB card (by mistake - I bought the v2 version
> instead of the supported v1 version), and I've just finished getting it 
> working
> under Linux, but spent the last day or so trying to figure out why it keeps
> dropping buffers even though the reception is perfect. As soon as I noticed
> that the lost data is always in PAGE_SIZE multiples, I figured I'd better 
> boot in
> plain Linux instead of Xen, and when I did that it worked perfectly.
> What happens if you boot dom0 with 'dom0_mem=max:1G' and limit the
> amount of memory
> Xen sees by using 'mem=4G' on the Xen command line?

That seems to make the problem go away. The machine itself has 5GB of memory in 
it, so (assuming an even spread) only 1/5 of allocations would come from >4GB 
memory right? This matches the missing pages of data in the resulting DMA 

Where should I start looking for the fix? The card is PCIe so I would have 
thought it would have supported DMA to memory > 4GB, is that the problem? I 
think one of my USB devices has the same problem too.

Btw, what is dom0_mem=max:1G supposed to do? Dom0 still has ~3.7GB memory 
allocated to it on boot.



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