kumquat-buildroot/board/qemu/arm-versatile/readme.txt
Yann E. MORIN ef3b031a81 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>
(cherry picked from commit 626c9705d2)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
2019-07-07 00:09:02 +02:00

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Run the emulation with:
qemu-system-arm -M versatilepb -kernel output/images/zImage -dtb output/images/versatile-pb.dtb -drive file=output/images/rootfs.ext2,if=scsi,format=raw -append "rootwait root=/dev/sda console=ttyAMA0,115200" -serial stdio -net nic,model=rtl8139 -net user
Or for the noMMU emulation:
qemu-system-arm -M versatilepb -kernel output/images/zImage -dtb output/images/versatile-pb.dtb -append "console=ttyAMA0,115200" -serial stdio -net user -net nic,model=smc91c111
The login prompt will appear in the terminal that started Qemu. The
graphical window is the framebuffer.
Tested with QEMU 2.12.0