Re: [Xen-devel] [PATCH] xen/mcfg: Call PHYSDEVOP_pci_mmcfg_reserved before PCI enumeration

[Ed Swierk <eswierk@xxxxxxxxxxxxxxxxxx>]

On Tue, Sep 22, 2015 at 5:35 AM, Ed Swierk <eswierk@xxxxxxxxxxxxxxxxxx> wrote:
> So if the contract is that Dom0 tells Xen about mmcfgs before the
> devices they cover, then Linux ought to call pci_mmcfg_reserved from
> (or immediately after) both pci_mmcfg_early_init() and
> pci_mmcfg_late_init().

Brainstorming possible approaches:

I don't see an obvious way to hook into those functions (or their
callers) without injecting Xen-specific code. Is there a precedent to
follow?

Alternatively, we could just call the equivalent of xen_mcfg_late()
from the existing xen_{add,remove}_device() notifiers. This would
generate a lot of useless pci_mmcfg_reserved hypercalls (number of
devices times number of mmcfg areas), but pci_mmcfg_arch_enable() in
Xen should happily ignore the redundant ones. The advantage of this
approach other than simplicity is that it makes the mmcfg -> device
setup ordering very explicit.

Any other ideas?

--Ed

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