Re: [PATCH v5 00/19] s390x: Add Full Boot Order Support

[Thomas Huth <thuth@redhat.com>]

On 08/11/2024 15.37, Thomas Huth wrote:
...
> And in case you're interested (it's maybe not so important since it's rather 
> unlikely that the users will do this), there is another issue when trying to 
> boot from multiple network devices where the first one has a DHCP server but 
> no bootfile:
> 
> qemu-system-s390x -nographic -accel kvm -m 2G -netdev user,id=n1 \
>   -device virtio-net-ccw,netdev=n1,bootindex=1 \
>   -netdev user,id=n2,tftp=/boot,bootfile=vmlinuz \
>   -device virtio-net-ccw,netdev=n2,bootindex=2 -d guest_errors
> 
> The firmware seems to panic while trying to request DHCP information from 
> the second boot device.

I had a look at this problem now, and the solution is as simple as this:

diff --git a/pc-bios/s390-ccw/virtio-net.c b/pc-bios/s390-ccw/virtio-net.c
--- a/pc-bios/s390-ccw/virtio-net.c
+++ b/pc-bios/s390-ccw/virtio-net.c
@@ -51,6 +51,8 @@ int virtio_net_init(void *mac_addr)
      void *buf;
      int i;

+    rx_last_idx = 0;
+
      vdev->guest_features[0] = VIRTIO_NET_F_MAC_BIT;
      virtio_setup_ccw(vdev);

Otherwise the rx_last_idx does not get reset to 0 when starting the 2nd 
network boot, so the code tries to access some ring data that contains 
garbage later. I'll send it as a proper patch...

  Thomas