Re: [Xen-users] amd-v -- passthrough supported?

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Mon, Jan 25, 2010 at 10:51:57AM -0800, 0bo0 wrote:
> On Mon, Jan 25, 2010 at 10:00 AM, Pasi Kärkkäinen <pasik@xxxxxx> wrote:
> > I'm not sure if AMD even has IOMMU capable hardware out yet?
> >
> > I think recently there was a patch to enable AMD IOMMU with Xen,
> > on "800" series chipsets.
> 
> i'm drowning in acronyms and lack of documentation ...
> 
> let's try this:
> 
> does Xen support whatever AMD cpus/chipsets DO have, that i'm
> currently using to successfully do pci-passthrough (which that wiki
> page seems to be about) to PV'd DomUs?
> 

Xen PCI passthrough to PV guests has been supported for years, and it 
doesn't require IOMMU or VT-d. On both Intel and AMD.

Xen PCI passthrough to PV guests was actually available years before 
there even was a VT-d spec!

The way it's done for PV guests can be a bit unsafe though, since the guest
gets DMA access and could use that maliciously..

> I keep being told "The VT-d specification states that all conventional
> PCI devices behind a PCIe-to-PCI bridge have to be assigned to the
> same domain." and to "refer to the VT-d" spec, but I'm not ON Intel,
> don't HAVE Vt-d, etc etc.
>

VT-d (or IOMMU in general) is required for PCI passthrough to HVM guests.
Xen requires IOMMU (VT-d on Intel) to do PCI passthrough to HVM guests.

I think IOMMU can also be used to do _secure_ PCI passthrough to PV guests.
(to fix the security problem I mentioned above).

-- Pasi


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