----- Original Message -----

On Mon, Jan 09, 2012 at 04:12:10PM +0000, Stefano Stabellini wrote:

quoted

On Mon, 9 Jan 2012, Konrad Rzeszutek Wilk wrote:

quoted

On Mon, Jan 09, 2012 at 11:39:44AM +0000, Stefano Stabellini
wrote:

quoted

I don't think we should add "PCI_XEN && SWIOTLB_XEN &&
X86_LOCAL_APIC &&
X86_IO_APIC && ACPI && PCI" to XEN either.
However it should be possible to add only the right
dependencies to the
right places.
In practice it should be sufficient to:

- make PCI_XEN depend on X86_LOCAL_APIC && X86_IO_APIC && ACPI;

Not good. You can make non-ACPI builds with PCI.

.. and you are missing CONFIG_PCI in there.

quoted

- make XEN_PCIDEV_FRONTEND and XEN_PCIDEV_BACKEND depend on
PCI_XEN;

OK. That sounds good.

quoted

- remove the 'ifdef CONFIG_ACPI' from arch/x86/pci/xen.c.

No.. same issue - non-ACPI builds can be with PCI.

quoted

Right.. in that case we should carefully replace the 'ifdef
CONFIG_XEN_DOM0' with 'ifdef CONFIG_ACPI' in arch/x86/pci/xen.c.

.. which I think I did at some point as part of cleanup and then
removed them since it peppered the xen.c with tons of #ifdef
CONFIG_ACPI.

What about PVonHVM. There is this nagging feeling in the back of my
head that turning CONFIG_XEN_DOM0 disables the CONFIG_PVHVM option?
Or something like that? Maybe it is the other way around?

It would seem we need to seperate the PVHVM  from DOM0. But the extra
complexity comes with Mukesh's PVonHVM Hybrid which can do dom0 stuff
with PVonHVM (should be searchable on xen-devel to find the patches).

They're currently separate, i.e. no problem with DOM0 off and PVHVM on,
or vice-versa afaict. I don't know anything about the hybrid though.

Ian also mentioned that we MUST have the XEN_PRIVILIGED option,
otherwise
we will cause a regression with the GRUB tools. So that must stay or
we need
provide a deprecation schedule for the next 3 years to remove it and
have patches in the GRUB toolchains.

Yeah, that's a bummer.

Either way, there is also the question of making sure that no
regressions
are introduced - so a lot of the CONFIG_* interdependencies will have
to be checked. I think that means checking CONFIG_XEN,
CONFIG_PRIVILIGED,
CONFIG_PVHVM, CONFIG_PCI, CONFIG_ACPI, CONFIG_XEN_BACKEND in various
combinations.

I guess if we did the s/XEN_DOM0/LOCAL_APIC && IO_APIC && ACPI/ in
arch/x86/pci/xen.c it would be pretty easy to review for equivalence.
Then keep CONFIG_PRIVILIGED, but drop XEN_DOM0 from everywhere else and
compile in the 3 files. I don't think it makes much sense to do it
though. XEN_DOM0 keeps things tidier now and might be useful later.

Oh, I forgot CONFIG_XEN_FRONTEND.. And I think that one can also
become
a module (ditto for XEN_BACKEND)

And everytime we did something to those we managed to mess them up so
we should be dilligient.

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