On 14 February 2016 at 23:12, Guenter Roeck [off-list ref] wrote:

Hi,

my qemu tests for arm64 fail to boot in linux-next, starting with next-20160209.
Primary error is

  VFS: Cannot open root device "(null)" or unknown-block(0,0): error -6
  Please append a correct "root=" boot option; here are the available partitions:
  Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)

but that doesn't mean much since I try to boot an initramfs.

A bisect attempt points to 'arm64: move kernel image to base of vmalloc area',
but that doesn't really help since some of the bisect attempts fail to build
with linker errors. Just for reference, a bisect log is attached.

Comparing console logs between 4.5-rc3 and next-20160212, one key difference is
that the kernel now displays

  Moving initrd from [88000000-889ae7ff] to [5d251000-5dbff7ff]

which was not the case before. Turns out RAM ends at 60000000, so the address
appears to be a bit odd (4.5-rc3 shows initramfs at a lower address).
My qemu test runs with 512MB RAM. If I increase the RAM size to 2G,
the "Moving" message is no longer displayed. However, I still get the same
error.

Qemu command line:

qemu-system-aarch64 -machine virt -cpu cortex-a57 -machine type=virt \
        -nographic -smp 1 -m 512 -kernel arch/arm64/boot/Image \
        -initrd rootfs.arm64.cpio -append "console=ttyAMA0"

Configuration is defconfig. Initramfs can be copied from
        https://github.com/groeck/linux-build-test/blob/master/rootfs/arm64/rootfs.arm64.cpio

Please let me know if there is anything I can do to help tracking down
the problem.

Hi Guenter,

Thanks for the detailed analysis. This looks like the same issue I fixed here:
http://thread.gmane.org/gmane.linux.ports.arm.kernel/477645

Regards,
Ard.