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Re: [Qemu-devel] Hitting 29 NIC limit


From: Avi Kivity
Subject: Re: [Qemu-devel] Hitting 29 NIC limit
Date: Thu, 14 Oct 2010 14:07:17 +0200
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.9) Gecko/20100921 Fedora/3.1.4-1.fc13 Lightning/1.0b3pre Thunderbird/3.1.4

 On 10/14/2010 12:54 AM, Anthony Liguori wrote:
On 10/13/2010 05:32 PM, Anjali Kulkarni wrote:

Hi,

Using the legacy way of starting up NICs, I am hitting a limitation after 29
NICs ie no more than 29 are detected (that's because of the 32 PCI slot
limit on a single bus- 3 are already taken up)
I had initially increased the MAX_NICS to 48, just on my tree, to get to
more, but ofcource that wont work.
Is there any way to go beyond 29 NICs the legacy way? What is the maximum
that can be supported by the qdev mothod?

I got up to 104 without trying very hard using the following script:

args=""
for slot in 5 6 7 8 9 10 11 12 13 14 15 16 17; do
for fn in 0 1 2 3 4 5 6 7; do
    args="$args -netdev user,id=eth${slot}_${fn}"
args="$args -device virtio-net-pci,addr=${slot}.${fn},netdev=eth${slot}_${fn},multifunction=on,romfile="
done
done

x86_64-softmmu/qemu-system-x86_64 -hda ~/images/linux.img ${args} -enable-kvm

The key is to make the virtio-net devices multifunction and to fill out all 8 functions for each slot.

This is unlikely to work right wrt pci hotplug. If we want to support a large number of interfaces, we need true multiport cards.

What's the motivation for such a huge number of interfaces?

--
error compiling committee.c: too many arguments to function




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