Re: [Xen-devel] [PATCH] VT-d: improve RMRR validity checking

[Alex Williamson <alex.williamson@xxxxxx>]

On Wed, 2010-03-10 at 10:40 +0800, Weidong Han wrote:
> Alex Williamson wrote:
> >
> > I have a system with what I consider to be a valid DRHD that's getting
> > tripped up on this patch.  The problem is that the DRHD includes an
> > IOAPIC scope, where the IOAPIC is not materialized on the PCI bus.  I
> > think Xen is being overzealous in it's validity checking and that this
> > is a valid configuration.  What do others think?  Are IOAPICs a
> > special case that we can allow to be non-existent on the PCI bus?
> >   
> Yes, IOAPIC can be not pci-discoverable. IOAPICs are only reported in 
> the "Include_all" DRHD, and our patch won't check if the device is 
> pci-discoverable or not for the "Include_all" DRHD. So I think the patch 
> is no problem unless IOAPIC is not included in the "Include_all" DRHD. 
> Can you post your boot logs?

Weidong,

That's a very subtle restriction, and I'm not sure how it works in
practice.  If I have a multi-IOH system, each with VT-d hardware, each
supporting interrupt remapping, each with one or more IOAPICs below
them, how can interrupt remapping work if we can only associate an
IOAPIC with the "include all" DRHD?  I'm confused.  Thanks,

Alex


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel