Date: Fri, 26 Sep 2025 23:44:16 +0200 From: Michael Tuexen <michael.tuexen@lurchi.franken.de> To: John Nielsen <lists@jnielsen.net> Cc: net@freebsd.org, virtualization@freebsd.org, np@freebsd.org Subject: Re: Chelsio (cxgbe) VF on FreeBSD guest under KVM requires -rxcsum Message-ID: <FA555678-F299-43BB-BF65-5A429CDF495E@lurchi.franken.de> In-Reply-To: <B648CE12-8D42-4978-A50B-DE5E7F39A512@jnielsen.net> References: <CF7D677F-2D3A-41B5-A3F1-0FCA844D206F@lurchi.franken.de> <B648CE12-8D42-4978-A50B-DE5E7F39A512@jnielsen.net>
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> On 26. Sep 2025, at 20:52, John Nielsen <lists@jnielsen.net> wrote: >=20 >> On Sep 26, 2025, at 1:46=E2=80=AFAM, Michael Tuexen = <michael.tuexen@lurchi.franken.de> wrote: >> =EF=BB=BF >>>=20 >>> On 26. Sep 2025, at 02:58, John Nielsen <lists@jnielsen.net> wrote: >>>=20 >>> Not sure if this is a known issue or even an issue on the FreeBSD = side but decided to ask here first. I=E2=80=99m happy to put in a bug = report if appropriate. >>>=20 >>> I have a hypervisor machine running Arch Linux with KVM, Qemu and = libvirtd. The machine has a Chelsio T520-CR adapter. I recently began = passing through virtual functions of the NIC to several of the guests I = run on the hypervisor. One of the guests runs Windows 11, and the change = was seamless. Two of the guests are running FreeBSD (14.3 or so). On = each of them the VFs were readily identified and configured (using DHCP = in one case), and ping and ARP appeared to work fine. However, TCP and = UDP traffic to the guests never received a response. After some = head-scratching and troubleshooting I discovered that running = =E2=80=9Cifconfig cxlv0 -rxcsum=E2=80=9D immediately allowed traffic to = flow as expected. >>=20 >> I don't have access to such a network card. Just to be clear: you are = running the =E2=80=9Cifconfig cxlv0 -rxcsum=E2=80=9D command inside the = guest running FreeBSD, right? >=20 > Yes. >=20 >> What is the peer, when you mention TCP and UDP do not work? Is it the = host running Linux? Is it another VM? Is it some external host? >=20 > My laptop on the same subnet primarily, but. Also tested from another = physical machine running FreeBSD. OK. That does not seem to be related to what I initially thought. Could you run tcpdump -i outgoing_interface -w laptop.pcap on your laptop and tcpdump -i cxlv0 -w vm.pcap on your vm at the same time and try to do some TCP based communication. Maybe two times, one time with ifconfig cxlv0 rxcsum and one time with = ifconfig cxlv0 -rxcsum. If you are fine with doing the measurements, you can send the .pcap = files to tuexen@freebsd.org <mailto:tuexen@freebsd.org>. At least I would like to understand what is going on. Best regards Michael >=20 >>> As workarounds go that isn=E2=80=99t terrible, but I was surprised = that the FreeBSD guests required this adjustment while the Windows one = did not. >>>=20 >>> As a point of reference I have another hypervisor machine that runs = FreeBSD 14-STABLE. It also has a >> So the host runs FreeBSD and you use bhyve to run some VM? >=20 > Yes >=20 >>> Chelsio T520-CR adapter. FreeBSD guests on that machine do not = require =E2=80=9C-rxcsum=E2=80=9D in order to use the Chelsio virtual = functions. >> The guests run FreeBSD-STABLE or Freebsd 14.3? >> What is the peer, when you mention TCP and UDP do not work? Is it the = host running Linux? Is it another VM? Is it some external host? >=20 > FreeBSD 14-STABLE circa 14.3 >=20 > Multiple off-box same-subnet peers in this scenario as well including = my laptop. >=20 > I=E2=80=99m aware that VF-to-PF communication is a special case. >=20 > JN
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