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[Xen-users] 10 GbE PCI passthrough

To: Xen Users <xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-users] 10 GbE PCI passthrough
From: Felix Reinel <freinel@xxxxxxx>
Date: Tue, 25 Jan 2011 17:30:04 +0100
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Dear all,

we are trying to get our virtual machines to work performant with our 10
GbE cards (lspci says: NetXen Incorporated NX3031 Multifunction
1/10-Gigabit Server Adapter (rev 42)).

When doing some benchmarks it was noticed that especially on the
receiving side, the virtualization layer hits a significant performance
impact and therefore we went for a PCI passthrough, so that the VMs can
talk directly to the network card.

The PCI device was hidden from the hostsystem via pciback and then
configured in a VM like this:

# PCI passthrough for network card
pci = [ '82:00.0' ]

in the config file under /etc/xen.

The hostsystem is SLES11-SP1, running Xen version 4, 64 bit. The VMs
running on it are all running RedHat 5.3 (paravirtualized), 32 bit.

The limitation we noticed is that doing it this way, it is only possible
to configure the passthrough for a single VM, booting up a second VM
with identical configuration shows that the device is already in use.
However what we would like to have in the end is to share the PCI device
accross all VMs.

Is this a technical limitation or do you have some advise? If not
possible, do you have any other tuning tips?

Best regards,

Felix Reinel               |  Web & Systems Administrator
Office: D132 ESO           |
Tel.:   +49-89-32006-171   |  Address:
Fax.:   +49-89-32006-677   |    European Southern Observatory
Mobile: +49-160-2956856    |    Karl-Schwarzschild-Strasse 2
E-Mail: freinel@xxxxxxx    |    D-85748 Garching bei Muenchen, Germany

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