Re: [Xen-devel] [PATCH 3/3] qemu-xen-trad: IGD passthrough: Expose vendor specific pci cap on host bridge.

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Mon, Jul 01, 2013 at 09:06:37AM -0400, Konrad Rzeszutek Wilk wrote:
> > >> >> Or just scan through the capabilities, and chain only the ones
> > >> >> that we want to "Whitelist" and the rest are to be blacklisted.
> > >> >> The rest can also have its values set to some bogus value 
> > >> >> (0xdeadbeef?)
> > >> >> Perhaps only when built with 'debug=y'.
> > >> >
> > >> >
> > >> > That sounds about right. Back when I first did the patch (in an old 
> > >> > qemu)
> > >> > there were no other capabilities on the piix4 host bridge so it was 
> > >> > simple.
> > >> > Not sure if other capabilities will be an issue now.
> > >>
> > >> It's still the case as for the IVB host bridge.
> > >> And from what I can find from the datasheet for the Haswell, it's
> > >> still the case.
> > >>
> > >> Note that the datasheet explicitly documents the offset of the
> > >> CAPABILITY registers.
> > >> I guess there will be code that rely on this offset that been publicly
> > >> documented.
> > >>
> > >> Btw. Ross, now that you appears to be the original author (sorry for
> > >> mess you up with Jean),
> > >> could you also comment on my rework proposal? Jan believe the current
> > >> form is not clean enough.
> > >>
> > >> Currently we use a whitelist of registers to pass-through.How do you
> > >> come up with the current list?
> > >> The shadow copy way appears to work for the current list.
> > >
> > > OK.
> > >> But what if we are going to need some special registers that cannot be
> > >> handled well? (e.g. has side effect for reading and cannot perform
> > >> read-back?)
> > >
> > > Hopefully the i915 driver in Linux will help in figuring out which
> > > ones of those are needed?
> > I remember the vendor cap fix only helps windows guest.
> 
> How was that diagnosed? Perhaps that information can be part of the source
> code to help in the future with diagnosiing which caps are needed and
> which ones can be blacklisted?
> 

I guess that's a question mostly for Ross/Jean as they're the original authors 
of the patch? 

-- Pasi


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel