kumquat-buildroot/board/qemu/mips32r2-malta/readme.txt
Yann E. MORIN 626c9705d2 board/qemu: ensure root is available before mounting it
On my machine, it happens once in a while that the virtualised machine
boots too fast for the rootfs to be available at the time the kernel
tries to mount it.

For example, board/qemu/arm-vexpress/readme.txt suggested changing
"-smp 1" up to "-smp 4". But doing so here causes a kernel panic:

    VFS: Cannot open root device "mmcblk0" or unknown-block(0,0): error -6
    Please append a correct "root=" boot option; here are the available partitions:
    1f00          131072 mtdblock0
     (driver?)
    1f01           32768 mtdblock1
     (driver?)
    Kernel panic - not syncing: VFS: Unable to mount root fs on
    unknown-block(0,0)

So, add the oh-so-useful 'rootwait' option to all kernel command lines
for qemu defconfigs.

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: Joel Stanley <joel@jms.id.au>
Cc: Mark Corbin <mark.corbin@embecosm.com>
Cc: Matt Weber <matthew.weber@rockwellcollins.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
2019-06-25 22:55:58 +02:00

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Run the emulation with:
qemu-system-mips -M malta -kernel output/images/vmlinux -serial stdio -drive file=output/images/rootfs.ext2,format=raw -append "rootwait root=/dev/hda" -net nic,model=pcnet -net user
The login prompt will appear in the terminal that started Qemu. The
graphical window is the framebuffer. No keyboard support has been
enabled.
Tested with QEMU 2.12.0