On Fri, Nov 18, 2016 at 05:17:34PM +0000, Gabriele Paoloni wrote:

quoted

-----Original Message-----
From: linux-kernel-owner at vger.kernel.org [mailto:linux-kernel-
owner at vger.kernel.org] On Behalf Of Bjorn Helgaas
Sent: 17 November 2016 18:00

quoted

+Static tables like MCFG, HPET, ECDT, etc., are *not* mechanisms for
+reserving address space!  The static tables are for things the OS
+needs to know early in boot, before it can parse the ACPI namespace.
+If a new table is defined, an old OS needs to operate correctly even
+though it ignores the table.  _CRS allows that because it is generic
+and understood by the old OS; a static table does not.

Right so if my understanding is correct you are saying that resources
described in the MCFG table should also be declared in PNP0C02 devices
so that the PNP driver can reserve these resources.

Yes.

On the other side the PCI Root bridge driver should not reserve such
resources.

Well if my understanding is correct I think we have a problem here:
http://lxr.free-electrons.com/source/drivers/pci/ecam.c#L74

As you can see pci_ecam_create() will conflict with the pnp driver
as it will try to reserve the resources from the MCFG table...

Maybe we need to rework pci_ecam_create() ?

I think it's OK as it is.

The pnp/system.c driver does try to reserve PNP0C02 resources, and it
marks them as "not busy".  That way they appear in /proc/iomem and
won't be allocated for anything else, but they can still be requested
by drivers, e.g., pci/ecam.c, which will mark them "busy".

This is analogous to what the PCI core does in pci_claim_resource().
This is really a function of the ACPI/PNP *core*, which should reserve
all _CRS resources for all devices (not just PNP0C02 devices).  But
it's done by pnp/system.c, and only for PNP0C02, because there's a
bunch of historical baggage there.

You'll also notice that in this case, things are out of order:
logically the pnp/system.c reservation should happen first, but in
fact the pci/ecam.c request happens *before* the pnp/system.c one.
That means the pnp/system.c one might fail and complain "[mem ...]
could not be reserved".

Bjorn