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[Xen-devel] [PATCH] force HPET support on buggy NVidia-based machines

While playing around with some cpufreq issues, I found out that Xen unstable 
is currently unable to use the HPET timer of my NVidia Nforce Pro-based 

Some research on the net revealed that quite a lot dual socket machines (i.e. 
workstations and small servers from Dell and HP) don't provide correct ACPI 
information about this timer, even though the HPET is present and functional. 
Very recent Linux kernels (starting from 2.6.23(?)) as well as LinuxBIOS 
therefore provide a workaround to enable the HPET anyway by scanning the PCI 
bus for suspicious devices and querying them directly. 

I've ported a part of this workaround to Xen. To enable it, apply the patch 
below and pass the cmd line arg "clocksource=hpet_nv" to Xen. This patch 
currently only covers some NVidia chipsets with the PCI ids shown in the 
patch.Other chipsets may need a similar procedure. The original Linux source 
even covers Intel (ICH4) and VIA chipsets. The patch below has been tested on 
my Tyan K8SE mainboard using a NForce Pro 2200 chipset and does it's job 
without woes so far.

I'm not sure if patches like this one are really a good idea for Xen, but 
maybe it helps some other people to run Xen more smoothly on their 
development machines.


Signed-off-by: Holger Steinhaus <hsteinhaus@xxxxxx>

Attachment: xen-3.3-unstable-hpet-force.diff
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