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[Xen-devel] iommu=1 by default?

To: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Keir Fraser <Keir.Fraser@xxxxxxxxxxxxx>
Subject: [Xen-devel] iommu=1 by default?
From: Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>
Date: Tue, 19 Jan 2010 09:59:16 +0000
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Thread-topic: iommu=1 by default?
Would it make sense to make "iommu=1" the default for xen 4.0?

I think Xen is rather more defensive these days about disabling iommu in the 
presence of broken BIOS tables, but there may conceivably still be machines it 
breaks boot on. I can't think of any subtle bugs the IOMMU could introduce if 
it's not explicitly in use by VMs -- and I don't believe anyone has seen any 
performance issues. [We could actually not fully turn the IOMMU on until the 
first VM that demands it.]

Would it make sense to turn it on by default in the release candidates? Or too 

IOMMU is clearly going to be a widely used feature in this release.


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