From: "Kay, Allen M" <allen.m.kay@intel.com>
To: Chris Wright <chrisw@sous-sol.org>
CC: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
       "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
       "jbarnes@virtuousgeek.org" <jbarnes@virtuousgeek.org>,
       "matthew@wil.cx" <matthew@wil.cx>
Date: Tue, 6 Oct 2009 13:15:54 -0700
Subject: RE: [PATCH ACS v3 1/1]
Thread-Topic: [PATCH ACS v3 1/1]
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> I was thinking that ACS could be enabled if an IOMMU is enabled.  Not a
> perfect fit, but seems reasonably close.

Chris, I'm working on a new version of the patch that incorporates iommu check.  I'm also adding a check for dom0 kernel as HW iommu is not visible to dom0.

Allen

-----Original Message-----
From: Chris Wright [mailto:chrisw@sous-sol.org] 
Sent: Wednesday, September 30, 2009 6:17 PM
To: Kay, Allen M
Cc: Chris Wright; linux-kernel@vger.kernel.org; linux-pci@vger.kernel.org; jbarnes@virtuousgeek.org; matthew@wil.cx
Subject: Re: [PATCH ACS v3 1/1]

* Kay, Allen M (allen.m.kay@intel.com) wrote:
> On the other hand, can we say VT-d PT mode is mainly for KVM
> virtualization use case?  If so, is it reasonable to say performance of
> host P2P in this mode is not of highest priority?

Guess it depends on the workload.  Would be helpful to identify a use
case that is p2p heavy (and then the impact of enabling ACS).

> If not, another option is to have a kernel boot parameter to
> configure an kernel boot instance to be either host kernel optimized or
> virtualization optimized.  I don't know whether this is a reasonable or
> not ...

I was thinking that ACS could be enabled if an IOMMU is enabled.  Not a
perfect fit, but seems reasonably close.

thanks,
-chris
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