Re: [Qemu-devel] qemu virtfs 9p not working on arm?

[Rich Felker]

On Thu, Aug 01, 2013 at 10:43:01AM +0100, Peter Maydell wrote:
> On 1 August 2013 00:25, Rich Felker <address@hidden> wrote:
> > I'm not sure whether this is a kernel problem or a qemu problem (or
> > even a user problem). The folks on OFTC #qemu suggested I email the
> > list and relevant section maintainers so that's what I'm doing -- hope
> > it's okay.
> >
> > I'm trying to boot qemu-system-arm with rootfs on 9p, and experiencing
> > the following error:
> 
> You don't say which board model you're using; I guess one
> of the PCI ones from the rest of the command line.

I'm using -M versatilepb -cpu arm1136-r2, also copied from the
Aboriginal Linux image since that's what the kernel was intended to
run on. I'm on the software side, not the hardware side, so I'm far
from an expert in understanding arm hardware variants. (I'm using qemu
to test software and make sure the arm-specific asm is correct, not to
test deployments.)

>From what I understand, this board has PCI. However, while doing some
searches based on your question, I found this which may be relevant:

http://lists.nongnu.org/archive/html/qemu-devel/2013-05/msg02237.html

Does this sound like it could be the issue?

> > | 9pnet: Installing 9P2000 support
> > | 9pnet_virtio: probe of virtio0 failed with error -2
> > | VFP support v0.3: implementor 41 architecture 1 part 20 variant b rev 4
> > | rtc-pl031 dev:e8: setting system clock to 2013-07-31 22:56:25 UTC 
> > (1375311385)
> > | 9pnet_virtio: no channels available
> > | VFS: Cannot open root device "root" or unknown-block(0,0): error -2
> > | Please append a correct "root=" boot option; here are the available 
> > partitions:
> > | 0b00         1048575 sr0  driver: sr
> > | Kernel panic - not syncing: VFS: Unable to mount root fs on 
> > unknown-block(0,0)
> >
> > That looks like ENOENT during the probe to me, but I can't find where
> > in the kernel source it's coming from. My configuration is:
> >
> > -append "root=root rw rootflags=rw,trans=virtio,version=9p2000.L 
> > -rootfstype=9p"
> > -fsdev local,id=root,path=$(pwd)/root,security_model=none
> > -device virtio-9p-pci,fsdev=root,mount_tag=root
> >
> > and this same configuration seems to work on x86. The kernels I'm
> > using are from the latest Aboriginal Linux images (3.10) and
> > /proc/config.gz seems to show that all the 9p/virtfs options are
> > enabled.
> 
> Do other virtio devices work?

I haven't really tried any devices since my aim is just software
testing, but I could try.

Rich