Re: [Xen-users] Unable to start Windows 8 HVM guest with Xen VGA Passthrough with Xen 4.2.1-pre

[Casey DeLorme <cdelorme@xxxxxxxxx>]

I am working with 32GB, so you probably don't want to model your configuration after mine.  My problem was memory was not being freed from Dom0 fast enough.

If you have already lowered Dom0 memory, checked it with xl info, and are still having problems launching, then it might be something else.

My assumption is the memory assigned in the configuration is not a 1:1 map to what is required.

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I decided to run some tests to see how Xen used my memory.

Starting with Dom0 and ipfire running, I ran xl info, got the diff, and then xl list and compared the two to find that xl info shows 500MB more memory used up.

I started Windows, and again roughly 500MB unaccounted for.

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So, based on that information I can assume Xen requires half a gigabyte to work with in the backend for its normal responsibilities.

The wiki has a best practices which shows 512MB set for Dom0:

http://wiki.xen.org/wiki/Xen_Best_Practices

I would try setting 512MB in your grub configuration like the above, check available RAM after your reload using `xl info`, making sure you have more than the 2GB set in the HVM configuration.

If it still doesn't work, then it must be something different.  You could also try lowering the memory in your DomU configuration as an alternative, just to see if it works.

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