Messages in this thread | | | Date | Tue, 29 Oct 2013 15:30:19 +0000 | From | "Jan Beulich" <> | Subject | Re: [v1 1/2] xen/p2m: Create identity mappings for PFNs beyound E820 and PCI BARs |
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>>> On 29.10.13 at 16:11, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote: > On Tue, Oct 29, 2013 at 02:55:13PM +0000, Jan Beulich wrote: >> >>> On 29.10.13 at 15:45, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote: >> > On Tue, Oct 29, 2013 at 08:23:30AM +0000, Jan Beulich wrote: >> >> >>> On 28.10.13 at 17:58, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote: >> >> > On Fri, Oct 25, 2013 at 04:08:19PM -0600, Bjorn Helgaas wrote: >> >> >> If you can look at PCI host bridge apertures instead of BARs, that >> >> >> would solve both problems. Reassigning those apertures is >> >> >> theoretically possible but is not even a gleam in our eyes yet. >> >> > >> >> > <nods> I think I have to have both (BARs and host bridge apertures) as when >> >> > we do PCI passthrough to a guest - we might do it without a bridge. >> >> >> >> Why? Aren't the host bridge ranges necessarily a superset of the >> >> individual devices' BARs? >> > >> > Yes. But when you pass in a PCI device to a PV guest you don't pass in the >> > bridge. Just the PCI device itself. >> >> Right you are. Which means that basing the whole logic on the >> PCI device BARs is likely wrong anyway, not just because it >> doesn't account for other MMIO ranges. > > Right, but that is OK. When you pass in a PCI device to a PV guest you > only care about that specific device driver being able to access its BARs.
Yes, but again - this is not the only possible way of allowing a guest access to MMIO. See the "iomem" config option.
Jan
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