runqemu: support multiple NICs

Emulating more than one network interface with runqemu is a bit tricky,
but possible. For example, the following leads to an emulated device with
eth0 and eth1:

QB_NETWORK_DEVICE_prepend = " \
    -device virtio-net-device,mac=52:54:00:12:34:03 \
"

or

QB_NETWORK_DEVICE_append = " \
    -device virtio-net-pci,mac=52:54:00:12:34:03 \
"

When booting Qemu with two NICs, the kernel does not know which
interface the specified ip=192.168.7.... command line argument
should be applied. This delays the boot process for a very long
time and a guest wihtout IP configuration.

This add two new configuraton parameters to runqemu:
QB_CMDLINE_IP_SLIRP and QB_CMDLINE_IP_TAP to explicitely specify the ip=
kernel command line arguments for tap and slirp mode.

Note: Simply adding "::eth0" broke some builds on the Yocto autobuilder.

Signed-off-by: Adrian Freihofer <adrian.freihofer@siemens.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 14 insertions, 0 deletions

diff --git a/meta/classes/qemuboot.bbclass b/meta/classes/qemuboot.bbclass
index 15a9e63f2b..54044c38da 100644
--- a/meta/classes/qemuboot.bbclass
+++ b/meta/classes/qemuboot.bbclass
@@ -36,6 +36,9 @@
 #                    Note, runqemu will replace @MAC@ with a predefined mac, you can set
 #                    a custom one, but that may cause conflicts when multiple qemus are
 #                    running on the same host.
+#                    Note: If more than one interface of type -device virtio-net-device gets added,
+#                          QB_NETWORK_DEVICE_prepend might be used, since Qemu enumerates the eth*
+#                          devices in reverse order to -device arguments.
 #
 # QB_TAP_OPT: netowrk option for 'tap' mode, e.g.,
 #             "-netdev tap,id=net0,ifname=@TAP@,script=no,downscript=no"
@@ -43,6 +46,15 @@
 #
 # QB_SLIRP_OPT: network option for SLIRP mode, e.g., -netdev user,id=net0"
 #
+# QB_CMDLINE_IP_SLIRP: If QB_NETWORK_DEVICE adds more than one network interface to qemu, usually the
+#                      ip= kernel comand line argument needs to be changed accordingly. Details are documented
+#                      in the kernel docuemntation https://www.kernel.org/doc/Documentation/filesystems/nfs/nfsroot.txt
+#                      Example to configure only the first interface: "ip=eth0:dhcp"
+# QB_CMDLINE_IP_TAP: This parameter is similar to the QB_CMDLINE_IP_SLIRP parameter. Since the tap interface requires
+#                    static IP configuration @CLIENT@ and @GATEWAY@ place holders are replaced by the IP and the gateway
+#                    address of the qemu guest by runqemu.
+#                    Example: "ip=192.168.7.@CLIENT@::192.168.7.@GATEWAY@:255.255.255.0::eth0"
+#
 # QB_ROOTFS_OPT: used as rootfs, e.g.,
 #               "-drive id=disk0,file=@ROOTFS@,if=none,format=raw -device virtio-blk-device,drive=disk0"
 #              Note, runqemu will replace "@ROOTFS@" with the one which is used, such as core-image-minimal-qemuarm64.ext4.
@@ -63,6 +75,8 @@ QB_DEFAULT_KERNEL ?= "${KERNEL_IMAGETYPE}"
 QB_DEFAULT_FSTYPE ?= "ext4"
 QB_OPT_APPEND ?= "-show-cursor"
 QB_NETWORK_DEVICE ?= "-device virtio-net-pci,netdev=net0,mac=@MAC@"
+QB_CMDLINE_IP_SLIRP ?= "ip=dhcp"
+QB_CMDLINE_IP_TAP ?= "ip=192.168.7.@CLIENT@::192.168.7.@GATEWAY@:255.255.255.0"
 
 # This should be kept align with ROOT_VM
 QB_DRIVE_TYPE ?= "/dev/sd"