Re: Emulate Rpi with QEMU fails

[Alex Bennée]

Thomas <74cmonty@gmail.com> writes:

> Hi,
>
> I'm trying to emulate Rpi with QEMU.
> I found
> [url=1]this[/url]
> arcticle in Raspberry Pi Geek documenting the steps including persistent
> storage on host.
>
> However when starting the emulation with command
> qemu-system-arm -M versatilepb -cpu arm1176 -m 256 -serial stdio -hda
> 2020-08-20-raspios-buster-armhf-lite.img -net
> "user,hostfwd=tcp::5022-:22" -dtb versatile-pb-buster.dtb -kernel
> kernel-qemu-5.4.51-buster -append "root=/dev/sda2 rootfstype=ext4 rw
> panic=1" -no-reboot

Let's start with the fact you are using a versatilepb machine type with
a versatilepb dtb and not the rasppi model. The manual goes into more
details about why you can't generally share kernels built for one ARM
system on another:

  https://qemu.readthedocs.io/en/latest/system/target-arm.html

Since that article was written we have added models for the -M raspi2
and -M raspi3 which might work better with a kernel written for it
although the emulation isn't complete.

> I get this error:
> VFS: Cannot open root device "sda2" or unknown-block(0,0): error -6
> Please append a correct "root=" boot option; here are the available
> partitions:
> 0100            4096 ram0
>  (driver?)
> 0101            4096 ram1
>  (driver?)
> 0102            4096 ram2
>  (driver?)
> 0103            4096 ram3
>  (driver?)
> 0104            4096 ram4
>  (driver?)
> 0105            4096 ram5
>  (driver?)
> 0106            4096 ram6
>  (driver?)
> 0107            4096 ram7
>  (driver?)
> 0108            4096 ram8
>  (driver?)
> 0109            4096 ram9
>  (driver?)
> 010a            4096 ram10
>  (driver?)
> 010b            4096 ram11
>  (driver?)
> 010c            4096 ram12
>  (driver?)
> 010d            4096 ram13
>  (driver?)
> 010e            4096 ram14
>  (driver?)
> 010f            4096 ram15
>  (driver?)
> 1f00           65536 mtdblock0
>  (driver?)
> Kernel panic - not syncing: VFS: Unable to mount root fs on
> unknown-block(0,0)
>
> I assume this is related to the content in fstab of RaspiOS:
> proc            /proc           proc    defaults          0       0
> PARTUUID=907af7d0-01  /boot           vfat    defaults          0       2
> PARTUUID=907af7d0-02  /               ext4    defaults,noatime  0       1
>
> Can you please advise how to fix this error?
>
> THX


-- 
Alex Bennée