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Date: Tue, 24 Jan 2012 11:21:41 +0100
From: Gerd Hoffmann <kraxel@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v4 0/6] save/restore on Xen
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: Jan Kiszka <jan.kiszka@siemens.com>, "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>, Avi Kivity <avi@redhat.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>

  Hi,

>>> We really should view RAM as just another device so I don't like the
>>> idea of
>>> propagating a global concept of "when RAM is restored" because that
>>> treats it
>>> specially compared to other devices.
>>>
>>> But viewing RAM as just another device, having Xen only restore a
>>> subset of
>>> devices should be a reasonable thing to do moving forward.

I don't think modeling device memory (i.e. vga vram) as something
independent from the device (vga) is a good idea.  Because it isn't.

>> To my understanding, QXL will break identically on Xen for the same
>> reason: the reset handler assumes it can deal with the VRAM as it likes.

Yes.  Some data structures for host <-> guest communication are living
in device memory, and a reset initializes these.

> QXL also has a VGA BIOS that it could use to initialize VRAM.  A similar
> change could be made for it.

Hmm.  Not sure this is a good idea.

cheers,
  Gerd