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Date: Thu, 29 Nov 2012 10:26:22 -0500 (EST)
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v4 03/11] dataplane: add host memory
 mapping code
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Anthony Liguori <aliguori@us.ibm.com>, Stefan Hajnoczi <stefanha@gmail.com>, qemu-devel@nongnu.org, Blue Swirl <blauwirbel@gmail.com>, khoa@us.ibm.com, Stefan Hajnoczi <stefanha@redhat.com>, Asias He <asias@redhat.com>

> > I don't understand.  If memory in the VGA region returns true from
> > memory_region_is_ram(), why would there be a problem?
> 
> If you change this memory but you don't update the display.
> Never happens with non buggy guests but we should catch and fail if
> it does.

Actually it _could_ happen with an MS-DOS guest that does the oh-so-retro

    DEF SEG=&HB800
    BLOAD "file.pic", 0

(I think).

Paolo