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Date: Wed, 24 Jul 2013 09:01:51 +0200
From: Gerd Hoffmann <kraxel@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: "Michael S. Tsirkin" <mst@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>, Paolo Bonzini <pbonzini@redhat.com>, Laszlo Ersek <lersek@redhat.com>, =?ISO-8859-1?Q?Andreas_F=E4rber?= <afaerber@suse.de>, David Gibson <david@gibson.dropbear.id.au>

On 07/24/13 08:01, Michael S. Tsirkin wrote:
> It turns out that some 32 bit windows guests crash
> if 64 bit PCI hole size is >2G.

Ah, *that* is the reason for winxp crashing with a 64bit hole.

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.

> Limit it to 2G for piix and q35 by default,
> add properties to let management override the hole size.
> 
> Examples:
> -global i440FX-pcihost.pci_hole64_size=137438953472

Do we really want specify this in bytes?  Using megabytes or gigabytes
instead looks more sane to me.

cheers,
  Gerd