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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 13:41:06 +0000
  • Accept-language: en-AU, en-US
  • Cc: "xen-devel@xxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxx>
  • Delivery-date: Tue, 10 Jun 2014 13:41:17 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xen.org>
  • Thread-index: Ac+DCNWNPHJYbVrFQ8CYCy7O42ilYwA+kV2AACaWUvAAA+f6AAABGpZA
  • Thread-topic: [Xen-devel] pci adapter not working in dom0. works under plain Linux.

> > > 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 transfers.
> That was my theory.
> >
> > 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.
> Ugh. They all should do the right job - that is using the DMA API.
> >
> > Btw, what is dom0_mem=max:1G supposed to do? Dom0 still has ~3.7GB
> memory allocated to it on boot.
> Oh, I think I mentioned that it should have been on the 'dom0' line but
> I meant Xen line.
> If you try removing the 'mem=4G' and just use 'dom0_mem=max:1G'
> please?
> That should limit the amount of memory the dom0 uses (it sees the
> rest of the E820 - but does not use it) - and that means that the
> drivers should _also_ use said below memory.
> I had some preliminary patches for the V4L API to use a better
> DMA ops, but I fear that they are bitrotten (and I can't even
> find them!). But lets try first determine if the workarounds
> work for you.
> >

That also produced no errors, so mem=4G fixes the problem, as does 


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