Re: [Xen-devel] [PATCH] xen/mcfg: Call PHYSDEVOP_pci_mmcfg_reserved before PCI enumeration

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 22.09.15 at 16:37, <konrad.wilk@xxxxxxxxxx> wrote:
> On Tue, Sep 22, 2015 at 08:11:41AM -0600, Jan Beulich wrote:
>> >>> On 22.09.15 at 16:03, <konrad.wilk@xxxxxxxxxx> wrote:
>> > On Tue, Sep 22, 2015 at 07:52:19AM -0600, Jan Beulich wrote:
>> >> >>> On 22.09.15 at 15:39, <konrad.wilk@xxxxxxxxxx> wrote:
>> >> > On Tue, Sep 22, 2015 at 06:26:11AM -0700, Ed Swierk wrote:
>> >> >> Any other ideas?
>> >> > 
>> >> > I like it - as it will update it right away. However we would need some
>> >> > extra smarts in Xen to reconfigure its view of the PCI device now that 
>> >> > the
>> >> > extended configuration space has become available.
>> >> 
>> >> What parts are you thinking of that would need updating (and
>> >> aren't getting updated already)?
>> > 
>> > The VF data. As before this call Xen might have not been able to
>> > get to the extended configuration.
>> 
>> I still don't understand: Afaics pci_add_device() updates everything
>> that may need updating already. And things appear to be working
>> fine with our kernel (where the MMCFG notification comes right out
>> of the x86 code earlier referred to), despite this meaning updates
>> to the data collected during early boot. I guess you'll need to be
>> more specific on what you see missing...
> 
> This is all ancient recollection of what I had seen a year or so ago
> so take it a with a cup of salt.

Urgh - a whole cup...

> I have one of those Intel machines where the MMCFG is not marked
> in the E820 but is in the ACPI and I remember getting frequent
> WARN_ON from Xen in the msi.c code when doing passthrough on the VF.
> I don't have the logs but my vague recollection was that Xen could
> not validate the VF's MSI-X because at the time it gathered the
> VF PCI device information the extended configurations were not
> available. This was prior to the XSA120 discovery so ancient
> code.

Well, VFs should not even show up prior to MMCFG getting
announced.

Jan


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