Re: [Xen-users] How to build Mini-OS for ARM

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 4 Jun 2019, Denis Obrezkov wrote:
> On 6/4/19 6:51 PM, Stefano Stabellini wrote:
> > On Tue, 4 Jun 2019, Julien Grall wrote:
> >> Hi Denis,
> >>
> >> On 6/4/19 1:19 PM, Denis Obrezkov wrote:
> >>>> If you want to use QEMU, may I recommend to use Xen arm64? I know this
> >>>> should work on QEMU and the setup is pretty much the same (the only
> >>>> difference is pretty much the compiler).
> >>>>
> >>>> Cheers,
> >>>>
> >>> Maybe I should. I wanted to try qemu-arm because bb-x15 has arm32 cores.
> >>> And also on arm64 I would need to use efi while on bb-x15 - u-boot. Or,
> >>> can I use qemu-arm64 and xen along with u-boot?
> >> From [1], it seems to be possible to use U-boot on QEMU arm64.
> >>
> >> Cheers,
> >>
> >> [1] https://github.com/u-boot/u-boot/blob/master/doc/README.qemu-arm
> > QEMU aarch64 works fine with u-boot. QEMU needs to be version 2.11 or
> > older. I use it like this:
> >
> > qemu-system-aarch64.2.11 \
> >     -machine virt,gic_version=3 \
> >     -machine virtualization=true \
> >     -cpu cortex-a57 -machine type=virt \
> >     -smp 4 -m 4096 \
> >     -serial mon:stdio \
> >     -bios /local/arm-vm/u-boot.bin \
> >     -netdev user,id=hostnet0,hostfwd=tcp::2223-:22 -device 
> > virtio-net-device,netdev=hostnet0,mac=52:54:00:e5:cc:31 \
> >     -drive 
> > if=none,file=/local/xenial-server-cloudimg-arm64-uefi1.img,id=hd0 -device 
> > virtio-blk-device,drive=hd0 \
> >     -device loader,file=/local/arm-vm/Image,force-raw=on,addr=0x45000000 \
> >     -device loader,file=/local/arm-vm/xen,force-raw=on,addr=0x49000000 \
> >     -device 
> > loader,file=/local/arm-vm/virt-gicv3.dtb,force-raw=on,addr=0x44000000
> >
> > where u-boot.bin is the u-boot binary I compiled by myself out of the
> > upstream u-boot repository. In u-boot, I chose the following kconfig
> > options:
> >
> > CONFIG_ARCH_QEMU=y
> > CONFIG_TARGET_QEMU_ARM_64BIT=y
> >
> > You can use the -device loader,file options to load files into memory at
> > the specified address, so that at the u-boot prompt you only have to
> > provide the boot command, such as:
> >
> > booti 0x49000000 - 0x44000000
> Ok, but I want to boot Linux built by me. To understand what is
> happening.

Sure. I don't think anything written above assumes you are using a Linux
kernel binary from a distro.


> Also, how can I debug the existing problem with hanging in
> qemu-arm - because this is very similar to what I have to solve during
> gsoc?

Where does it hang exactly? I don't use QEMU with a debugger often, but
you can connect gdb to QEMU if that's what you'd like to do. Normally, I
just add enough printks to Xen to figure out where it gets stuck. It is
pretty easy because if it's an early boot hang, then it is still all
single threaded and easy to follow.

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