Re: [Xen-devel] Re: PCI passthrough stopped working, brainache!

[Andy Burns <xen.lists@xxxxxxxxxxx>]

On 12 October 2011 09:01, Andy Burns <xen.lists@xxxxxxxxxxx> wrote:

> Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> wrote:
>
>> So it works now right?
>
> No.
>
> I think I remember what was the test I did before the boot that
> started working again

I didn't get much time to test this today ... reverted to same Xen and
kernel versions that worked briefly last night.

I discovered that (despite what I answered earlier) the PCI tuners
don't work in dom0 under Xen, they only work if the dom0 is booted  as
baremetal.

If I reboot from dom0 from baremetal with the PCI cards working into
Xen without powering off, it doesn't "magically" leave the PCI cards
in a state that allows them to work in the domU.

The thing which *seemed* to put it into a good mood last night was
booting dom0 with serial console and the domU with the PIC cards but
without the PCIe card, but that made no difference today.

I'm beginning to follow Konrad's thoughts that there is a specific
sequence of events, that persists in hardware state across soft
reboots, occasionally ending up with functioning PCI cards.

Is the fact that the PCI cards fail in dom0 under Xen a hint?  Any
debugging I can do with the tuners from the dom0 rather than the domU
with passthrough?

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