Re: PCI Device Assignment status

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On Fri, Sep 3, 2010 at 9:54 AM, Rodrigo Campos <rodrigo@xxxxxxxxxxx> wrote:
> Hi!
>
> I wanted to know the status of PCI device assignment.
>
> As far as I can see in the webpage and in the mailing list, it seems to be
> working ok if you have VT-d support on the motherboard and cpu. But if it isn't
> too much trouble, I wanted some confirmation about this, since I'm not sure and
> I don't want to buy hardware to test this when there is no way it's going to
> work :)

Yes, it works if you have VT-d support (Intel) or AMD IOMMU (note this
is different than the AMD GART that's often used as an IOMMU).  The
Intel boxes are a lot easier to find.

> Also, I wanted to confirm that there is no limit in the maximun PCI cards that
> could be given to a guest (like VMWare which only lets you give at most 2 cards
> to a guest, if I'm not wrong) and which version of qemu-kvm/Linux kernel I need
> for propper support.

The only limit I'm aware of is the number of slots on a bus (32), a
few of which are used by qemu emulated devices and can't be removed.
Any of the 0.12 releases should work fine.  Also note that there are
also device and driver dependencies that can be far more subtle in
whether the device can work with passthrough or not.  Things like
whether it has device dependent registers in pci config space, if the
driver expects specific capabilities at certain offsets, if it's a
multi-function device that shares nvram and uses the function as an
index offset, drivers that assume a bridge topology for a given
vid/did, etc...   SR-IOV devices are designed for this, so should
work, otherwise you might also post the cards you'd like to use and
see if anyone has experience with them.

Alex
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