Xen + linux 6.1.0-rc8, network to guest VM not working after commit ad7f402ae4f466647c3a669b8a6f3e5d4271c84a fixing XSA-423

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

Hi Ross / Juergen,

I just updated my linux kernel to the latest of Linus his tree which included 
commit ad7f402ae4f466647c3a669b8a6f3e5d4271c84a fixing XSA-423.

Unfortunately when using this kernel I can't SSH anymore into the Xen guest I 
start, but I don't see any apparent failures either.
A straight revert of the commit ad7f402ae4f466647c3a669b8a6f3e5d4271c84a makes 
networking function normally again.

I have added some of the logging below, perhaps it at gives some idea off the 
state around the Xen network front and backend.

Any ideas or a test patch that I could run to shed some more light on what is 
going on ?

--
Sander




Some of the logging from dom0 dmesg:

[  149.520585] xen_bridge: port 1(vif1.0) entered blocking state
[  149.520594] xen_bridge: port 1(vif1.0) entered disabled state
[  149.520678] device vif1.0 entered promiscuous mode
[  151.221975] xen-blkback: backend/vbd/1/51712: using 1 queues, protocol 1 
(x86_64-abi) persistent grants
[  151.601458] vif vif-1-0 vif1.0: Guest Rx ready
[  151.601476] xen_bridge: port 1(vif1.0) entered blocking state
[  151.601478] xen_bridge: port 1(vif1.0) entered forwarding state


output xenstore-ls regarding vif for the Guest:

    vif = ""
     1 = ""
      0 = ""
       bridge = "xen_bridge"
       feature-ctrl-ring = "1"
       feature-dynamic-multicast-control = "1"
       feature-gso-tcpv4 = "1"
       feature-gso-tcpv6 = "1"
       feature-ipv6-csum-offload = "1"
       feature-multicast-control = "1"
       feature-rx-copy = "1"
       feature-rx-flip = "0"
       feature-sg = "1"
       feature-split-event-channels = "1"
       feature-xdp-headroom = "1"
       frontend = "/local/domain/1/device/vif/0"
       frontend-id = "1"
       handle = "0"
       hotplug-status = "connected"
       ip = "192.168.1.6"
       mac = "00:16:3e:49:0e:fa"
       multi-queue-max-queues = "8"
       online = "1"
       script = "/etc/xen/scripts/vif-bridge"
       state = "4"
       type = "vif"

    vif = ""
     0 = ""
      backend = "/local/domain/0/backend/vif/1/0"
      backend-id = "0"
      event-channel-rx = "9"
      event-channel-tx = "8"
      feature-gso-tcpv4 = "1"
      feature-gso-tcpv6 = "1"
      feature-ipv6-csum-offload = "1"
      feature-rx-notify = "1"
      feature-sg = "1"
      handle = "0"
      mac = "00:16:3e:49:0e:fa"
      mtu = "1500"
      multi-queue-num-queues = "1"
      request-rx-copy = "1"
      rx-ring-ref = "524"
      state = "4"
      trusted = "1"
      tx-ring-ref = "523"
      xdp-headroom = "0"


ifconfig output for the guest interface on dom0 side:

vif1.0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 32  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 49  bytes 2058 (2.0 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0