Re: [Qemu-devel] [Qemu-arm] help on how to emulate rasbperry pi 2

[Mats Malmberg]

Hello, thank you for your quick response!

It helped me to get a little bit further, but unfortunately the problem 
persists. 
I now get some output from the kernel startup, but I think that it is unable to 
find the provided sd-card image.

Here's what I've tried (the most successful setup):
1. download and deflate jessie/jessie-lite image (I tried both distros)
2. mount the boot partition and copy the following files to host: kernel7.img, 
kernel.img and bcm2709-rpi-2-b.dtb
3. mount the rootfs partition. Open the file /etc/ld.so.preload and comment out 
the line /usr/lib/arm-linux-gnueabihf/libarmmem.so (which is the only line 
present in the file.)
4. execute the command 
qemu-system-arm -M raspi2  -kernel kernel7.img -sd 
2016-02-09-raspbian-jessie.img -append "rw earlyprintk loglevel=8 
console=ttyAMA0,115200 dwc_otg.lpm_enable=0 root=/dev/mmcblk0p2" -dtb 
bcm2709-rpi-2-b.dtb -serial stdio

the resulting terminal printout : 

WARNING: Image format was not specified for '2016-02-09-raspbian-jessie.img' 
and probing guessed raw.
         Automatically detecting the format is dangerous for raw images, write 
operations on block 0 will be restricted.
         Specify the 'raw' format explicitly to remove the restrictions.
Warning: Orphaned drive without device: 
id=sd0,file=2016-02-09-raspbian-jessie.img,if=sd,bus=0,unit=0
VNC server running on '127.0.0.1;5900'
Uncompressing Linux... done, booting the kernel.
...
lots of kernel output
...
[    6.306894] sdhci-pltfm: SDHCI platform and OF driver helper
[    6.335521] ledtrig-cpu: registered to indicate activity on CPUs
[    6.338465] hidraw: raw HID events driver (C) Jiri Kosina
[    6.341004] usbcore: registered new interface driver usbhid
[    6.341768] usbhid: USB HID core driver
[    6.346873] Initializing XFRM netlink socket
[    6.348012] NET: Registered protocol family 17
[    6.350974] Key type dns_resolver registered
[    6.352810] Registering SWP/SWPB emulation handler
[    6.360245] registered taskstats version 1
[    6.374999] vc-sm: Videocore shared memory driver
[    6.397370] uart-pl011 3f201000.uart: no DMA platform data
[    6.428165] VFS: Cannot open root device "mmcblk0p2" or unknown-block(0,0): 
error -6
[    6.429208] Please append a correct "root=" boot option; here are the 
available partitions:
[    6.430848] 0100            4096 ram0  (driver?)
[    6.431718] 0101            4096 ram1  (driver?)
[    6.432348] 0102            4096 ram2  (driver?)
[    6.433101] 0103            4096 ram3  (driver?)
[    6.434627] 0104            4096 ram4  (driver?)
[    6.435317] 0105            4096 ram5  (driver?)
[    6.435995] 0106            4096 ram6  (driver?)
[    6.436749] 0107            4096 ram7  (driver?)
[    6.437507] 0108            4096 ram8  (driver?)
[    6.438159] 0109            4096 ram9  (driver?)
[    6.438853] 010a            4096 ram10  (driver?)
[    6.439562] 010b            4096 ram11  (driver?)
[    6.440193] 010c            4096 ram12  (driver?)
[    6.440815] 010d            4096 ram13  (driver?)
[    6.441439] 010e            4096 ram14  (driver?)
[    6.442065] 010f            4096 ram15  (driver?)
[    6.443003] Kernel panic - not syncing: VFS: Unable to mount root fs on 
unknown-block(0,0)
[    6.444949] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.1.17-v7+ #838
[    6.445837] Hardware name: BCM2709
[    6.448200] [<800180c0>] (unwind_backtrace) from [<80013b88>] 
(show_stack+0x20/0x24)
[    6.449477] [<80013b88>] (show_stack) from [<80555028>] 
(dump_stack+0x80/0x98)
[    6.450490] [<80555028>] (dump_stack) from [<80551540>] (panic+0xa4/0x204)
[    6.451641] [<80551540>] (panic) from [<80777384>] 
(mount_block_root+0x1a8/0x260)
[    6.452802] [<80777384>] (mount_block_root) from [<80777614>] 
(mount_root+0xec/0x110)
[    6.453878] [<80777614>] (mount_root) from [<807777a0>] 
(prepare_namespace+0x168/0x1c8)
[    6.454982] [<807777a0>] (prepare_namespace) from [<80776f90>] 
(kernel_init_freeable+0x270/0x2bc)
[    6.456243] [<80776f90>] (kernel_init_freeable) from [<80550968>] 
(kernel_init+0x18/0xfc)
[    6.457378] [<80550968>] (kernel_init) from [<8000f858>] 
(ret_from_fork+0x14/0x3c)
[    6.459706] ---[ end Kernel panic - not syncing: VFS: Unable to mount root 
fs on unknown-block(0,0)

I know that in some of my previous attempts (before I contacted you guys), I 
was able to get similar result. At that time an mmcblk device was listed among 
the available partitions, but the kernel was unable to mount it.

I'm having problem to identify the cause (since as I mentioned earlier this is 
not really my domain).
I've also tried (without any positive results)
- mark the boot partition as bootable with fdisk (does not seem to make any 
difference)
- use kernel.img instead of kernel7.img (does not provide any kernel printout, 
but still says that it has an orphaned drive and hangs indefinetly after saying 
VNC server running)
- create a image with 'qemu-img create raw jessie.img 4G' and use dd to copy 
original image into jessie.img file, and the provide qemu with format=raw.
- make the above qemu-system-arm invocation with -hda 
2016-02-09-raspbian-jessie.img instead of -sd
- make the above qemu-system-arm invocation with -drive 
file=2016-02-09-raspbian-jessie.img,format=raw,if=sd instead of -sd


Do you have any suggestions on how to proceed with my troubleshooting?
Are you able to explain what seems to be the problem (and possible cause)?

Thank you for your help, really appreciated!

Best regards
Mats


________________________________________
From: Andrew Baumann address@hidden
Sent: Wednesday, February 24, 2016 7:51 PM
To: John Snow; Peter Maydell; Mats Malmberg
Cc: address@hidden; QEMU Developers
Subject: RE: [Qemu-devel] [Qemu-arm] help on how to emulate rasbperry pi 2

> From: John Snow [mailto:address@hidden
> Sent: Wednesday, 24 February 2016 10:28 AM
> On 02/24/2016 01:04 PM, Andrew Baumann wrote:
> >> From: Peter Maydell [mailto:address@hidden
> >> Sent: Wednesday, 24 February 2016 9:49 AM
> >>
> >> On 24 February 2016 at 15:40, Mats Malmberg
> <address@hidden>
> >> wrote:
> >>>
> >>> Hello all!
> >>>
> >>> TL;DR : Is the raspi2 machine ready to use? If yes, how do I use it with
> >>> ordinary rpi distros? If not, what is the best way to emulate raspberry
> >>> pi 2 via Qemu?
> >>
> >> Hi; I've cc'd the main qemu-devel list and Andrew Baumann who
> contributed
> >> the rpi2 support. I know there are still some missing pieces to be
> >> added later but I forget the details.
> >
> > There are still a number of missing pieces (including display and USB) which
> I hope to submit soon, but you should be able to boot Linux with a serial
> console. Brief instructions are at the end of this page:
> https://github.com/0xabu/qemu/wiki
> >
> > BTW, instead of -hda you need to pass -sd for the image file.
> >
> > Cheers,
> > Andrew
> >
>
> Is it worth changing the default interface for the "raspi2" board to be
> SD so that "-hda xxxxx" mounts an SD card?
>
> Or do we support using that for an imagined S/ATA interface? (BCM2836
> doesn't have SATA, right?)

Oh, in fact I am already setting that, so perhaps -hda does already work. Mats' 
problem is most likely just that he's not seeing/enabling the serial console.

Andrew