https://bugzilla.novell.com/show_bug.cgi?id=422081
User lverhaegen@novell.com added comment
https://bugzilla.novell.com/show_bug.cgi?id=422081#c3
Luc Verhaegen changed:
What |Removed |Added
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Status|NEW |NEEDINFO
Info Provider| |novell.com-pnt@ladisch.de
--- Comment #3 from Luc Verhaegen 2008-09-03 04:05:15 MDT ---
You're using VT3108, so the video memory is sitting off the CPU and not the
northbridge. All memory accesses have to go over HT to the CPU, which is a
huuge pain.
The system BIOS lies to the kernel, and tells us that ram starts at 0x00000000
and has the actual RAM Size minus the reserved FB size. This reserved FB lives
nicely at the top of actual RAM, and it is just the BIOS that tells us that it
is not there, while it is.
So we map this bit of ram directly, and then get massively fast FB access for
free.
Apparently this breaks on Xen and it apparently also breaks with some more
intrusive kernel versions.
I would need to know how Xen stops me from mapping this area, as it is all
Xen's doing. A plain linux kernel is just happy with us mapping /dev/mem
anyway.
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