From mboxrd@z Thu Jan  1 00:00:00 1970
From: Gerd Hoffmann <kraxel@redhat.com>
Subject: Re: [PATCH v3 11/11] igd: move
 igd-passthrough-isa-bridge creation to machine init
Date: Thu, 07 Jan 2016 08:38:59 +0100
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To: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: igvt-g@ml01.01.org, xen-devel@lists.xensource.com, Eduardo Habkost <ehabkost@redhat.com>, "Michael S.
	Tsirkin" <mst@redhat.com>, qemu-devel@nongnu.org, Cao jin <caoj.fnst@cn.fujitsu.com>, vfio-users@redhat.com, Paolo Bonzini <pbonzini@redhat.com>, Richard Henderson <rth@twiddle.net>
List-Id: xen-devel@lists.xenproject.org

  Hi,

> One thing I don't like about this is that it is going to skip the checks
> done in xen_pt_initfn.

Hmm?  Those checks are still done when you assign a igd ...

> For example it is going to create the isa bridge,
> even if there is going to be an error loading the vga bios or if the
> device specified is not even an Intel graphic card.

Creating the special igd-isa-bridge is no longer tied to actually
assigning a igd, but to the igd-passthru=3Don machine option being present
(and machine type being 'pc').

xen_pt_initfn checks that igd-passthru=3Don is set in case it finds a igd
device is assigned, that will make sure the igd-isa-bridge is present.

But, yes, you can create a igd-isa-bridge now even when not assigning a
igd device, either by specifying igd-passthru=3Don or using -device.  I
fail to see why this is a problem though, care to explain?

Also note that moving this to machine init nicely handles the fact that
the igd-isa-bridge is needed on 'pc' only, not on 'q35'.  If you don't
want create the igd-isa-bridge in machine init, what is your alternative
suggestion to handle this?

cheers,
  Gerd