Hello,

I’m trying to setup a guest VM with QEMU v5.1.0

I execute it in the following way:

/usr/bin/qemu-system-x86_64 -name flatcar_production_qemu -machine
q35,accel=kvm -cpu host,pmu=off -qmp unix:/tmp/qmp-socket,server,nowait -m
2048M -netdev tap,id=macvtap4,vhost=on,vhostfds=3,fds=4 -device
driver=virtio-net-pci,netdev=macvtap4,mac=e2:ef:88:bc:ae:62,disable-modern=false,mq=on,vectors=4,romfile=
-device
virtio-blk-pci,disable-modern=false,drive=rootfs,scsi=off,config-wce=off,romfile=,serial=rootfs
-drive id=rootfs,file=rootfs.img,aio=threads,format=raw,if=none -device
virtio-serial-pci,disable-modern=false,id=serial0,romfile= -device
virtconsole,chardev=charconsole0,id=console0 -chardev
socket,id=charconsole0,path=console.sock,server,nowait -object
rng-random,id=rng0,filename=/dev/urandom -device
virtio-rng-pci,rng=rng0,romfile= -vga none -no-user-config -nodefaults
-nographic -daemonize -object memory-backend-ram,id=dimm1,size=2048M -numa
node,memdev=dimm1 -realtime mlock=off -kernel
flatcar_production_pxe.vmlinuz -initrd flatcar_production_pxe_image.cpio.gz
-append "root=/dev/disk/by-id/virtio-rootfs ip=192.168.43.48:
:169.254.1.1:255.255.255.255::eth0:none:172.31.0.10 tsc=reliable
no_timer_check= rcupdate.rcu_expedited=1 i8042.direct=1 i8042.dumbkbd=1
i8042.nopnp=1 i8042.noaux=1 noreplace-smp= reboot=k console=hvc0
console=hvc1 cryptomgr.notests= net.ifnames=0 pci=lastbus=0 -smp 2”

The network interface which is connected to is a MacVTap in bridge mode.
The tap device under /dev exists and it is named tap5 and I pass there its
file descriptor. I also use the vhostfds to improve performance.

What I get is that if I try to ping the interface with IP 192.168.43.48, the
ICMP packets reach the tap5 device. Nothing however is written into the tap
device by the OS. So here the impossibility for the OS to communicate.

Any idea what could be wrong?

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