Using Qemu for BMC with a TAP interface

[Patrick Venture]

On Wed, Dec 1, 2021 at 9:08 AM Cédric Le Goater <clg at kaod.org> wrote:

> On 12/1/21 16:59, Peter Foley wrote:
> > The container system we're using (https://research.google/pubs/pub43438
> <https://research.google/pubs/pub43438>) provides a set of FDs connected
> to a pre-configured TAP device, so I don't think manual bridge
> configuration is an option.
>
> ok. That's interesting. You are running QEMU BMC machines (Nuvotons and
> Aspeed ?)
> wrapped in containers. Why BMC machines?
>

We're running BMC machines to validate BMC firmware.


>
> I guess we could reproduce the setup with a single instance to check
> issues but
> it's a lot of work for an uncommon scenario.
>
> Thanks,
>
> C.
>
>
> >
> > On Tue, Nov 30, 2021 at 7:54 PM Patrick Venture <venture at google.com
> <mailto:venture at google.com>> wrote:
> >
> >
> >
> >     On Mon, Nov 22, 2021 at 12:14 AM Cédric Le Goater <clg at kaod.org
> <mailto:clg at kaod.org>> wrote:
> >
> >         Hello,
> >
> >         On 11/22/21 08:20, Joel Stanley wrote:
> >          > On Thu, 18 Nov 2021 at 20:35, Patrick Venture <
> venture at google.com <mailto:venture at google.com>> wrote:
> >          >>
> >          >> Hi;
> >          >>
> >          >> We're working on wiring up our Qemu BMC via a TAP
> configuration, and we're not seeing packets inside the Nuvoton NIC itself
> (a level of debugging we had to enable).  We're using the npcm7xx SoC
> device,
> >          >>
> >          >> -nic
> tap,fds=4:5:6:7:8:9:10:11,id=net0,model=npcm7xx-emc,mac=58:cb:52:18:b8:f7
> >          >>
> >          >> For the networking parameters, where the tap fds are valid.
> I was curious if any of y'all got qemu networking working for your BMC
> SoCs, either Aspeed or Nuvoton?
> >          >
> >          > I've not tried using the -nic tap option with file
> descriptors. It's
> >          > not quite clear what you're trying to do, or what your full
> setup
> >          > looks like.
> >
> >         yes. could you explain please ? It is simpler to run with a
> netdev bridge
> >         backend :
> >
> >             -net nic,macaddr=C0:FF:EE:00:00:03,netdev=net0 -netdev
> bridge,id=net0,helper=/usr/libexec/qemu-bridge-helper,br=virbr0
> >
> >
> >     Thanks for the replies and help.  I don't know why my mail didn't
> decide this should go in my inbox.  Probably user error on my part in the
> filters.
> >
> >     Peter, would a network bridge simplify life?  I imagine the file
> descriptor approach is because of the framework configuring Qemu, but
> wanted to ask.
> >
> >
> >
> >         Thanks,
> >
> >         C.
> >
> >          >
> >          > I did test it out just now with a manually created tap
> interface:
> >          >
> >          > sudo ip tuntap add test0 mode tap group netdev
> >          > sudo ip link set test0 up
> >          > sudo tcpdump -i test0
> >          >
> >          > And then when I fired up a qemu instance,
> >          >
> >          > qemu-system-arm -nographic -M romulus-bmc -kernel
> arch/arm/boot/zImage
> >          > -dtb arch/arm/boot/dts/aspeed-bmc-opp-romulus.dtb -initrd
> arm.cpio.xz
> >          > -nic tap,ifname=test0,id=net0
> >          >
> >          > I could see packets being decoded by the tcpdump instance (my
> laptop
> >          > is 'voyager', qemu came up as fe80::5054:ff:fe12:3456):
> >          >
> >          > $ sudo tcpdump -i test0
> >          > tcpdump: verbose output suppressed, use -v[v]... for full
> protocol decode
> >          > listening on test0, link-type EN10MB (Ethernet), snapshot
> length 262144 bytes
> >          > 15:10:32.683930 IP6 voyager > ip6-allrouters: ICMP6, router
> >          > solicitation, length 16
> >          > 15:10:33.655994 IP6 voyager.mdns > ff02::fb.mdns: 0 [2q] PTR
> (QM)?
> >          > _ipps._tcp.local. PTR (QM)? _ipp._tcp.local. (45)
> >          > 15:10:37.795242 IP6 fe80::5054:ff:fe12:3456 > ip6-allrouters:
> ICMP6,
> >          > router solicitation, length 16
> >          > 15:11:05.688413 IP6 voyager.mdns > ff02::fb.mdns: 0 [2q] PTR
> (QM)?
> >          > _ipps._tcp.local. PTR (QM)? _ipp._tcp.local. (45)
> >          > 15:11:07.499841 IP6 voyager > ip6-allrouters: ICMP6, router
> >          > solicitation, length 16
> >          > 15:11:11.079030 IP6 fe80::5054:ff:fe12:3456 > ip6-allrouters:
> ICMP6,
> >          > router solicitation, length 16
> >
> >
> >     Thanks, so with the ftgmac100 nic, you're able to talk to qemu via
> tap.  I didn't see any obvious differences in the npcm7xx_emc device.
> >
> >          >
> >          > I've cc'd Cédric as he is the king of qemu command lines.
> >          >
> >          > Cheers,
> >          >
> >          > Joel
> >          >
> >          >
> >          >
> >          >
> >          >
> >          >
> >          >>
> >          >> Patrick
> >
>
>
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