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Is there a way to set up a 10Gb-capable virtual ethernet port in a guest VM (RHEL) without using virtio ?

I have to put some kind of RHEL7 in a guest VM but the kernel used in there has UDP fragmentation bugs when using virtio ethernet devices. The problems don't appear with the e1000 device (but then I'm capped at 1Gb/s), and no amount of futzing around settings can unbreak this virtio bug (and I can't upgrade the guest kernel).

Is there another way with virsh/libvirt than declaring a virtio device (e.g.):

<interface type="bridge">
  <mac address="00:00:32:32:b0:32"/>
  <source bridge="bridge_5"/>
  <target dev="vnet24"/>
  <model type="virtio"/>
  <driver name="vhost"/>
  <alias name="net0"/>
  <address type="pci" domain="0x0000" bus="0x00" slot="0x03" function="0x0"/>
</interface>

That would be able to send/receive 10Gb/s traffic ?

The host server has 2 x 10GbE (BCM57416) ethernet controlers, if it can help (can it ?)...

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  • Which virtio bug? My searches are only finding noise about the removal of UDP Fragmentation Offload from RHEL 8 kernels, and some old issue about UDP checksums and dhcpd.
    – John Mahowald
    Nov 27, 2022 at 0:40
  • With UDP offload enabled I can see the pcap packets sent through without fragmentation although all interfaces are MTU 9000. Disabling all offloads (guest, host, everywhere) makes the guest VM send fragmented UDP packets but the first fragment has a wrong size field... I haven't located the specific bug in any bug DB but a more recent guest kernel doesn't show the problem. I can't seem to work around this (and I can't upgrade this guest), so I wanted to try something else than e1000 and virtio but that could still hit 10Gb.
    – Touisteur EmporteUneVache
    Nov 28, 2022 at 14:58
  • Please edit your question to add the kernel versions in question, and which are working versus not. And, IPv4 or IPv6?
    – John Mahowald
    Nov 30, 2022 at 23:30

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