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Intel processor specifications list the virtualization feature vt-d as a processor feature of the xeon 5500 series but not of the 5600 series. Vt-d is needed for io virtualization.

How does vt-d relate to intel processors, there is no information.


I just learned the answer from an intel marketing manager and thought I should document it here for the common benefit.

vt-d is an Intel chipset feature which enables iommu / directed io in virtualized environments, eg. xen. It is not a processor feature like vt-x. vt-d is neede for io passthrough to guests, like PCI passthrough.

A complete answer obtained from an intel marketing manager is given below.

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you can read about VT-D here.

bascially it's

  1. I/O device assignment. This feature allows an administrator to assign I/O devices to VMs in any desired configuration.

  2. DMA remapping. Supports address translations for device DMA data transfers.

  3. Interrupt remapping. Provides VM routing and isolation of device interrupts.

  4. Reliability features. Reports and records system software DMA and interrupt erros that may otherwise corrupt memory of impact VM isolation.

th entire poitn of which is to provide hardware support for the functions that hypervisors currently do in software. This also requires chipset/bios support so it is not drop in replaceable

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Yes, the question was what to look for when one wants to use vt-d. I did not find any information about this topic and listed vt-d as a processor capability of the intel xeon 5500s but not the 5600s which is just plain wrong: its a chipset feature. That's what the problem is about: You need a vt-d enabled mobo/bios/chipset plus I suppose a vt-x capable cpu. But thanks for the Answer because one of the links is very helpful. (Bios config for vt-d,…). – deploymonkey May 18 '10 at 13:24

I'm not an expert of this, but as far as I understood, the vt-d capabilities relies on the hardware between the memory and the device needed to be virtualized. In the xeon 55XX the vt-d is in the north bridge, in the xeon 5600 i think it's integrated in the processor. I'm not an expert, so take them with a pinch of salt ;)

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A detailed paper on vt-d is here… – Pier May 18 '10 at 13:22
up vote 0 down vote accepted

Update: I just got myself escalated to an intel marketing manager for europe. I didn't anticipate that, but he was very helpful.

vt-d is a chipset feature, so is wrong in the statement that vt-d is a feature of the xeon 5500. The manager was astonished of that statement in ark.

As long as You use a vt-d capable chipset, he said the 5500 and 5520 and didn't know others from the top of his head, with a vt-d enabled motherboard bios (this is often a problem) and add a processor that is virtualization capable (he confirmed this for the xeon 5500, 5600, I didn't ask for any other series), You should get it to work.

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