Re: [Xen-users] SR-IOV

[Liwei <xieliwei@xxxxxxxxx>]

On 27 November 2011 10:23, Achala Aryal <arya2595@xxxxxxxxxxxxxxxxxx> wrote:
> what is virtual slot things then?

I'm assuming that you're referring to this:
http://wiki.xen.org/xenwiki/VTdHowTo#line-199

Recall that PCI passthrough is basically assigning a physical PCI card
to a virtual machine. Within the VM are virtual slots, virtual
counterparts of the physical PCI slots you plug your cards into. So
when you assign a PCI device to a virtual slot, its like slotting the
physical PCI card into the VM's virtual PCI slot.

See Slide 24 - 29 of
http://www.valinux.co.jp/documents/tech/presentlib/2009/jls/multi-function_a.pdf
for some nice graphical representations (although the graphics refer
to virtual functions, the idea is very similar).

>
> and also lets say,
> I have pci NIC in dom0 and  two different PCIe device and are assigned it
> directly to two different VMs.
>
>
> is there any communication problem between them? like PCI to PCIe device?
>

In general, there should be no problems, except for some device and
BIOS quirks. For lower level considerations like overheads and fringe
scenarios, you'll have to ask the xen devs.

One thing to note is that, it is likely your PCI slots are provided by
a PCIe-to-PCI bridge. If that is so, last I heard, all PCI devices
behind the same bridge must be assigned to the same domain:

http://www.ibm.com/developerworks/linux/library/l-pci-passthrough/#hypervisor_support

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