Re: [Qemu-devel] [PATCH v3 1/9] kvm: remove hard dependency on pci

[Cornelia Huck <cohuck@redhat.com>]

On Wed, 26 Jul 2017 10:26:23 +0200
Cornelia Huck <cohuck@redhat.com> wrote:

> On Wed, 26 Jul 2017 08:52:44 +0200
> Thomas Huth <thuth@redhat.com> wrote:

> > Since this missed the 2.10 freeze anyway and we've got some more time to
> > discuss it: I still think it would be much cleaner to move the functions
> > from kvm-all.c that use these PCI functions into a separate file
> > kvm-pci.c instead and compile that only with CONFIG_PCI=y. That way we
> > likely also could prevent that more dependencies on CONFIG_PCI creep
> > into kvm-all.c again at later points in time.
> > 
> > I've now had a closer look, and it seems like the only affected
> > functions are kvm_irqchip_add_msi_route() and
> > kvm_irqchip_update_msi_route() ... and these seems only to be used in
> > code we would not care about on s390x with CONFIG_PCI=n. So could you
> > please have at least a try to move these two functions (and other
> > related msi functions) to a new file kvm-pci.c instead to see whether
> > that would work, too?  
> 
> I can try, as this missed the 2.10 boat anyway.
> 
> The code contains some parts that are not relevant in all cases (msi
> routes if we don't use pci, adapter routes for anything not
> s390x, ...), but I don't think trying to rip this out would be much of
> an improvement. I'll try the minimal (well, not quite as minimal as
> this patch) route instead.

I tried this; but it turned out to be one of those cases where you pull
on a stick and then find half a tree attached to it... Much of the code
is used by all routing variants, and I ended up exposing so many
functions that it was just ugly and unreadable.

The variant I'm now going with is keeping the original approach and
adding a pci_available variable, which I also use in the patch that
exposes the zpci facility patch only when pci is compiled in. I'll try
to post this after lunch.