Re: [Xen-devel] RFC: [PATCH 1/3] Enhance platform support for PCI

[Manish Jaggi <mjaggi@xxxxxxxxxxxxxxxxxx>]

On Monday 23 February 2015 09:50 PM, Jan Beulich wrote:
> > > > On 23.02.15 at 16:46, <ian.campbell@xxxxxxxxxx> wrote:
> > On Mon, 2015-02-23 at 15:27 +0000, Jan Beulich wrote:
> > > > > > On 23.02.15 at 16:02, <ian.campbell@xxxxxxxxxx> wrote:
> > > > Is the reason for the scan being of segment 0 only is that it is the one
> > > > which lives at the legacy PCI CFG addresses (or those magic I/O ports)?
> > > Right - ideally we would scan all segments, but we need Dom0 to
> > > tell us which MMCFG regions are safe to access,
> > Is this done via PHYSDEVOP_pci_mmcfg_reserved?
> Yes.
>
> > >   and hence can't
> > > do that scan at boot time. But we also won't get away without
> > > scanning, as we need to set up the IOMMU(s) to at least cover
> > > the devices used for booting the system.
> > Which hopefully are all segment 0 or aren't needed until after dom0
> > tells Xen about them I suppose.
> Right. With EFI one may be able to overcome this one day, but the
> legacy BIOS doesn't even surface mechanisms (software interrupts)
> to access devices outside of segment 0.
>
> > >   (All devices on segment zero are supposed to
> > > be accessible via config space access method 1.)
> > Is that "the legacy ....  or magic ..." again?
> Yes (just that there are two of them).
Ian/Jan,
Have you reached a conclusion?
> Jan
>
>
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