[Xen-users] continued question on Xen 3d virtualization with IOMMU

["Tao Shen" <taoshen1983@xxxxxxxxx>]

Hi , Xen-User group:

I am planning on a new system to run 4 VMs within Xen, hopefully after 3d(openGL, Direct3d) working in Xen or windows.

I have some questions after extensively googling for it:

Mats, you said that you don't need Xen-aware drivers in DomU if the system has IOMMU.

now on the subject of hardware support, currently we have Vt-x and AMD-v and that's hardware assisted CPU virtualization. what's coming up in Penryn is the Extended Page Table(EPT) and AMD Barcelona's Nested Page Table(NPT) for help with hardware assisted memory virtualization as far as I understand it.

Now question #1, EPT and NPT should only help performance of the VM, it doesn't help with 3d right? What I understand is that you need IOMMU instead which is a chipset feature instead of a CPU feature.

on the subject of IOMMU support:  The Bearlake Q35 chipset will come with Intel VT-d(intel's version of IO virt), expected in a few months, Bearlake P35 is already out.  On the AMD side, I have heard that current chipsets already have IOMMU support built in.(probably not AMD IOMMU spec 
1.2 just released, but at least 1.0)

Now question #2,  which AMD chipsets(there is a bunch of Nforce, and ATI chipsets) that Xen developers know of that has IOMMU working?(I have heard that the GART and DEV together is a fully functional IOMMU unit)  and if I were to get an Athlon X2 AM2 chip with that chipset mobo, technically, I can get the 3d working right? but without the benefits of NPT which later comes with Barcelona(which is also AM2 socket compatible)

Question #3:  you said that Xen aware GPU drivers can help 3d accleration in domU VMs if the GPU driver is open source.  Intel's GPUs are all open source now, when can users expect to have Xen work with Intel's embedded GPUs like GMA950 and X3100s?

Now question #4: not that important, but how much performance benefits do you think you can get from the addition of NPT and EPT?,  VMware argues that the first gen VT-x and AMD-V sometimes made the VMs slower.  If EPT doesn't add much and AMD's got IOMMU already working, there is no reason for me to wait for Penryn IMHO.

Thanks for your time and thank you in advance for helping me with those questions,

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