Re: [Qemu-devel] Help needed to run Exynos 4210 linux kernel on qemu?

[Igor Mitsyanko]

On 09/04/2012 02:13 AM, Jean-Christophe DUBOIS wrote:
> Hi,
>
> I am trying to run linux over qemu-system-arm emulating a nuri or
> smdkc210 Exynos 4210 based board.
>
> To do this I fetched the last qemu (from git://git.qemu.org/qemu.git)
> and built it with "./configure --target-list=arm-softmmu.
>
> Then I fetched the latest linux image for samsung processors (from
> git://git.kernel.org/pub/scm/linux/kernel/git/kgene/linux-samsung.git)
> and built it using exynos4_defconfig config file.
>
> Then I tried to run the 2 together:
>
> $ qemu-system-arm -kernel zImage -append "console=ttySAC0,115200n8
> root=/dev/ram rw earlyprintk" -serial stdio -M smdkc210 -initrd rootfs.img
> smdkc210 board supports only 2 CPU cores. Ignoring smp_cpus value.
> VNC server running on `127.0.0.1:5900'
> Booting Linux on physical CPU 0
> Linux version 3.6.0-rc3 (address@hidden) (gcc version 4.6.3
> (Ubuntu/Linaro 4.6.3-1ubuntu5) ) #1 SMP PREEMPT Mon Sep 3 22:44:05 CEST
> 2012
> CPU: ARMv7 Processor [410fc090] revision 0 (ARMv7), cr=10c5387d
> CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing instruction cache
> Machine: SMDKC210
> bootconsole [earlycon0] enabled
> Truncating RAM at 40000000-7fffffff to -6f7fffff (vmalloc region overlap).
> Memory policy: ECC disabled, Data cache writealloc
>
> The kernel hangs here because it got a data abort exception while trying
> to print the "next" message (which is "CPU EXYNOS4210 (id 0x43210211)").
> The data abort is generated somewhere in the console_unlock() function.
>
> I tried the same thing with some less up to date source code of qemu
> and/or linux with the same result. I even tried the linaro versions of
> qemu and linux without luck.
>
> So there has to be something I am doing wrong. I would really appreciate
> it if you could point me in the right direction.
>
> Thanks.
>
> JC

Hello, Jean!

I've just tried to do the same thing you're trying to do, it works for 
me if I remove earlyprintk from append. Probably this is due to the fact 
that kernel expects uart0 to be configured by u-boot prior to kernel 
start execution. Interestingly, if you change default exynos4_defconfig 
CONFIG_DEBUG_S3C_UART0 to, for example, CONFIG_DEBUG_S3C_UART2 in linux 
kernel configuration, everything starting to work fine even with 
earlyprintk.

But using ramdisks is always a pain for me, I would suggest you two 
different approaches:

1) The most convenient way is to use emulated SD card for rootfs 
storage. There is no SD card support for exynos4210 in current QEMU 
master, but you can apply SD host controller patches I attached to this 
email to get this support. These patches already have been thoroughly 
reviewed in qemu-devel mailing list and hopefully would be applied to 
QEMU master soon enough.
If you want to use SD card instead of RAMDISK, apply these patches to 
QEMU master with "git am", and enable MMC/SD support in linux kernel 
configuration (it is disabled by default in exynos4_defconfig). You need 
to check CONFIG_MMC, CONFIG_MMC_SDHC, CONFIG_MMC_SDHCI_S3C and 
ONFIG_MMC_SDHCI_S3C_DMA.
Then you can launch QEMU with -sd /path/to/your/rootfs and, for example, 
append line -append "root=/dev/mmcblk0 rootfstype=ext4 rw rootwait".

2) If you want to work only with what current QEMU master has, you can 
use network filesystem as rootfs, but only for smdkc210 board (nuri 
board doesn't have any net devices). You're gonna have to check these 
options in Linux configuration:
CONFIG_NET, CONFIG_PACKET, CONFIG_INET, CONFIG_IP_PNP, 
CONFIG_IP_PNP_DHCP, CONFIG_NETDEVICES, CONFIG_SMSC911X, CONFIG_NFS_FS, 
CONFIG_ROOT_NFS.
Then, if, for example, you have directory /mnt/nfsroot exported by NFS 
server on your host machine, you can launch QEMU guest with following 
command line:

qemu-system-arm -kernel ./zImage -M smdkc210 -append 
"console=ttySAC0,115200n8 ip=dhcp root=/dev/nfs 
nfsroot=10.0.2.2:/mnt/nfsroot/ rw" -serial stdio

Also, maybe you noticed, graphic support is disabled in 
exynos4_defconfig by default. To enable it, check these options in Linux 
configuration:
CONFIG_DRM, CONFIG_DRM_EXYNOS, CONFIG_DRM_EXYNOS_DMABUF, 
CONFIG_DRM_EXYNOS_FIMD. You can also check CONFIG_LOGO to get a fancy 
penguins during guest VM startup. And if you need to start X server on 
your guest VM, you also need to enable UNIX domain sockets in linux 
kernel CONFIG_UNIX.

0001-hw-introduce-standard-SD-host-controller.patch
Description: Text Data

0002-exynos4210-Added-SD-host-controller-model.patch
Description: Text Data