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RE: [Xen-devel] [VTD][patch 0/5] HVM device assignment using vt-d

To: "Guy Zana" <guy@xxxxxxxxxxxx>, "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] [VTD][patch 0/5] HVM device assignment using vt-d
From: "Kay, Allen M" <allen.m.kay@xxxxxxxxx>
Date: Thu, 31 May 2007 10:43:47 -0700
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Thread-topic: [Xen-devel] [VTD][patch 0/5] HVM device assignment using vt-d
>Just FYI.
>Neocleus' pass-through patches performs the "change polarity" trick.
>With changing the polarity, our motivation was to reflect the 
>allocated device's assertion state to the HVM AS IS.
>Regarding the performance, using a USB 2.0 storage device 
>(working with DMA), a huge file copy was compared when working 
>in pass-through, and when working in native (on the same OS), 
>the time differences were negligible so I'm not sure yet about 
>the impact of doubling the number of interrupts. The advantage 
>of changing the polarity is the simplicity.
>Anyways, We'll release some patches during the day so you 
>could give your comments.

How do you handle DMA buffers without hardware support?  Did you
modify the device driver in HVM to get the machine physical address?

Sounds like the conflict is only limited to the vt-d interrupt
patch (vtd3.patch) - which is a relatively small part vt-d patch set.

Once your patch is released, I will take a look at it.


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