Re: [Qemu-devel] 64-bit MMIO aperture expansion

[Marcel Apfelbaum]

Hi Laszlo, Michael

On 09/21/2018 08:41 PM, Laszlo Ersek wrote:
> On 09/21/18 19:20, Michael S. Tsirkin wrote:
> > On Fri, Sep 21, 2018 at 06:01:30PM +0300, Marcel Apfelbaum wrote:
> > > On 09/20/2018 05:49 PM, Laszlo Ersek wrote:
> > > > Now, there's another complication, obviously -- machine type compat. In
> > > > commit 9fa99d2519cb, we added the "pci_hole64_fix" compat property. I
> > > > assume the additional fix I'm proposing requires another compat
> > > > property?
> > > We have to, is a guest visible change. I really don't like these compat
> > > properties, but I don't see a way around it.
> > Well does it only affect ACPI? Or other stuff? ACPI changes
> > are mostly safe without need for compat things.
> My understanding is that it affects ACPI only:
>
> (1) q35_host_get_pci_hole64_end() is only referenced in the code when it
> is set as a getter for the PCI_HOST_PROP_PCI_HOLE64_END property, in
> q35_host_initfn() [hw/pci-host/q35.c].
>
> (2) i440fx_pcihost_get_pci_hole64_end() is only referenced in the code
> when it is set as a getter for the same PCI_HOST_PROP_PCI_HOLE64_END
> property, in i440fx_pcihost_initfn() [hw/pci-host/piix.c].
>
> (3) The PCI_HOST_PROP_PCI_HOLE64_END property is only fetched in
> acpi_get_pci_holes() [hw/i386/acpi-build.c].
>
> (4) acpi_get_pci_holes() is only called in acpi_build()
> [hw/i386/acpi-build.c].
>
> (5) The resultant "pci_hole64" structure is passed to build_dsdt() only.

Yes, it affects only ACPI. But the ACPI tables are guest visible.
On the other hand it can be seen as a "firmware update" and not
as a machine change.

As I previously stated I prefer to avoid another compat property.
Thanks,
Marcel

> Thanks
> Laszlo