Re: Problem with creating a root device

[Peter Maydell]

On Mon, 21 Sep 2020 at 09:11, Roger James <roger@beardandsandals.co.uk> wrote:
>
> Peter,
> Thank you for your prompt response. It does look like the failure in the scsi 
> driver is what is causing the root device not to be created. I can see that 
> there has been an issue raised on this at the qemu-rpi-kernel repo on github.
>
> I am puzzled about why the kernel thinks there is a scsi device present.

The kernel is correct -- the versatilepb QEMU model will by default
plug an LSI SCSI controller into its PCI bus.

> Could this be an issue with the device tree that I am using?

PCI devices don't appear in the device tree, because PCI is
a probeable bus so the kernel can automatically identify
what devices are there.

> I have now  tried yet another config, still no success.
>
> -drive 
> "file=2020-05-27-raspios-buster-lite-armhf.img,if=none,index=0,media=disk,format=raw,id=disk0"
>  \
> -device "virtio-blk-pci,drive=disk0,disable-modern=on,disable-legacy=off" \

What is the failure mode here? Does the guest kernel identify
that there is a virtio-blk device on the PCI bus? If not,
probably the problem is that the kernel doesn't have the
necessary virtio drivers built in -- you could fix that if
you're in a position to rebuild the kernel. Or you could try
the megasas scsi device, which might have a driver in your kernel.

> I think I need to either disable the scsi driver in the kernel, or
> stop qemu emulating one on the pci bus.

My guess is that this won't be necessary -- I think the kernel's
driver for the scsi card has failed in initialization, which will
mean the kernel will just act as if the scsi card wasn't there
at all.

thanks
-- PMM