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Date: Wed, 24 Jul 2013 17:07:42 +0300
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] pc: limit 64 bit hole to 2G by default
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>, Eduardo Habkost <ehabkost@redhat.com>, qemu-devel@nongnu.org, Isaku Yamahata <yamahata@valinux.co.jp>, Alex Williamson <alex.williamson@redhat.com>, Gerd Hoffmann <kraxel@redhat.com>, Laszlo Ersek <lersek@redhat.com>, Andreas =?iso-8859-1?Q?F=E4rber?= <afaerber@suse.de>, David Gibson <david@gibson.dropbear.id.au>

On Wed, Jul 24, 2013 at 03:18:01PM +0200, Paolo Bonzini wrote:
> Il 24/07/2013 15:14, Michael S. Tsirkin ha scritto:
> > On Wed, Jul 24, 2013 at 02:59:18PM +0200, Paolo Bonzini wrote:
> >> Il 24/07/2013 11:51, Michael S. Tsirkin ha scritto:
> >>>> Current seabios uses a slightly different approach: the 64bit hole is
> >>>> present only in case it is actually used to map bars there, and seabios
> >>>> tries to fit everything into the 32bit hole first.
> >>>
> >>> Yes. But this doesn't work with device hotplug.
> >>
> >> Are you preserving that behavior for older machine types?
> > 
> > Older machine types (1.5 and back) don't report PCI hole size to guests
> > so there's nothing to preserve.
> 
> So pc-1.5 and older always use the SeaBIOS ACPI tables, even on new
> QEMU?  (I guess I should review your ACPI table patches).
> 
> Paolo

Yes.

> > This means there's not much I can do for pc-1.5: as before this
> > patch, hotplug of devices with large BARs won't work,
> > and some windows guests will crash if a device with a huge
> > BAR is added statically.
> > 
> >> (Also, what happens if you do -global i440FX-pcihost.pci_hole64_size=0?
> >>  Does that return a _CRS with only the 32-bit hole)?
> >>
> >> Paolo
> > 
> > Yes.
> >