Re: [Xen-devel] [PATCH v2 2/4] x86/MSI-X: access MSI-X table only after having enabled MSI-X

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.04.15 at 19:41, <konrad.wilk@xxxxxxxxxx> wrote:
> On Mon, Apr 13, 2015 at 10:05:14AM +0100, Jan Beulich wrote:
>> You mentioning XSA-120 and its addendum - are these requirements
>> for the problem to be seen? I admit I may have tested a PV guest
>> only with an SR-IOV VF (and only a HVM guest also with an "ordinary"
>> device), but I'd like to be clear about the validity of the connection.
> 
> No. I just tried with v4.0-rc5 (and then also v4.0) and just 
> using SR-IOV to make this simpler.

Good.

> With staging  + two of your patches:
> a10cc68 TODO: drop //temp-s
> 1b8721c x86/MSI-X: be more careful during teardown
> 
> When trying to enable SR-IOV I get this error:

Okay, this definitely works for me, albeit I know I had to do
adjustments to avoid running into the (debug) warning you've
hit. But (looking at the call stack) it surely would be a mistake to
set up an MSI-X IRQ on the device without first enabling MSI-X
on the it (i.e. the error returned could be considered legitimate).
While we may want the hypervisor to cope with this (by enabling
MSI-X on this path, which I'd have to add to that patch), is this
hypervisor change perhaps uncovering a pv-ops kernel issue (in
that other than what drivers/pci/msi.c does as of the commit
mentioned in the description of that second patch some Xen-
specific path fails to enable MSI-X before setting up any of the
entries)?

Jan


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