Re: [V9fs-developer] [Qemu-devel] QEMU dies on any attempt to load a Linux kernel module when using a 9P rootfs

[Christopher Covington <cov@codeaurora.org>]

Hi Dominique,

On 08/22/2014 08:49 AM, Dominique Martinet wrote:
> Hi,
> 
> Christopher Covington wrote on Fri, Aug 22, 2014 at 08:37:52AM -0400:
>> Thanks for the pointer to this patch. I think I started this kernel half way
>> through the 3.16 merge window. The last non-cherry-picked patch I have is:
>>
>> commit 6d87c225f5d82d29243dc124f1ffcbb0e14ec358
>>
>> So I do have the change you pointed out. Nevertheless, I'll reconfirm with the
>> latest torvalds/master.
> 
> Right, so you already do have it. I don't think there's been anything
> else 9P related recently, so it probably will not help much -- sorry for
> blindly assuming it would be this.
> 
> Actually reading the error message now, "no channels available" is
> printed when virtio doesn't find any match in device name so it would
> look like the mount name doesn't match maybe?
> 
> Could we get your exact qemu command line to confirm? (the name that
> needs to match is /dev/root here, used for booting as root= and for qemu
> as mount_tag)

I re-transposed Richard's command line to my environment and it worked. Thanks
for pointing me in that direction. For the record, I used:

$dir/bin/x86_64-linux-gnu/qemu-system-x86_64 \
  -m 1024 \
  -kernel $dir/boot/x86_64-linux-gnu/bzImage-x86_64 \
  -append 'root=/dev/root init=/sbin/x86_64-linux-gnu/init rootfstype=9p
rootflags=trans=virtio,version=9p2000.L ro console=ttyS0' \
  -serial stdio \
  -fsdev local,id=root,path=$dir,security_model=none \
  -device virtio-9p-pci,fsdev=root,mount_tag=/dev/root \
  -monitor none

$dir/bin/x86_64-linux-gnu/qemu-system-arm \
  -M virt \
  -cpu cortex-a15 \
  -m 1024 \
  -kernel $dir/boot/arm-linux-gnueabihf/Image \
  -append 'root=/dev/root init=/sbin/arm-linux-gnueabihf/init rootfstype=9p
rootflags=trans=virtio,version=9p2000.L ro console=ttyAMA0' \
  -serial stdio \
  -fsdev local,id=root,path=$dir,security_model=none \
  -device virtio-9p-device,fsdev=root,mount_tag=/dev/root \
  -monitor none

$dir/bin/x86_64-linux-gnu/qemu-system-aarch64 \
  -M virt \
  -cpu cortex-a57 \
  -m 1024 \
  -kernel $dir/boot/aarch64-linux-gnu/Image \
  -append 'root=/dev/root init=/sbin/aarch64-linux-gnu/init rootfstype=9p
rootflags=trans=virtio,version=9p2000.L ro console=ttyAMA0' \
  -serial stdio \
  -fsdev local,id=root,path=$dir,security_model=none \
  -device virtio-9p-device,fsdev=root,mount_tag=/dev/root -monitor none

Christopher

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