Re: [Xen-devel] Re: Comments on Xen bug 1732

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> On 16.03.11 at 14:50, Gianni Tedesco <gianni.tedesco@xxxxxxxxxx> wrote:
> On Wed, 2011-03-16 at 08:22 +0000, Jan Beulich wrote:
>> >>> On 15.03.11 at 19:30, Gianni Tedesco <gianni.tedesco@xxxxxxxxxx> wrote:
>> > Furthermore this used to work on xen 3.4 but fails on 4.1 so it seems to
>> > be a regression. One other notable change is the assignments of the
>> > MSI-X vectors that I see when hitting the Q debug key:
>> > 
>> > On 3.4:
>> > (XEN) 04:10.0 - dom 1   - MSIs < 66 74 82 >
>> > 
>> > On 4.1:
>> > (XEN) 04:10.1 - dom 0   - MSIs < 117 118 119 >
>> 
>> dom 1 on 3.4 vs dom 0 on 4.1? And different functions? Doesn't
>> look like a 1:1 comparison to me.
> 
> Yeah they are different machines with the same SR-IOV NIC (similar
> enough hardware wise). But the point is the different assigned domains,
> bear in mind that in both cases the function in question is assigned to
> a guest at the time the debug key was pressed.

And even iommu=verbose doesn't produce anything more
informative? Something must be going wrong during the
assignment...

Are the kernels in host and guest exactly the same in both the
3.4 and the 4.1 cases? Using pciback or pci-stub?

>> > Any ideas?
>> 
>> Not really. Despite me not thinking that the change in question
>> (that introduced the WARN_ON()s) has any functionality impact
>> (it's really only about trying to write protect certain MMIO
>> ranges, with the WARN_ON()s reporting that this didn't work as
>> expected) - did you try reverting it (and its follow-up fixes)?
> 
> No change.

With that, the regression then clearly must be elsewhere, and
I'm afraid we're having to hope that Intel folks will take a look.

Jan


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