Re: [Qemu-devel] 9pfs troubles (was Re: [PATCH 1/4] hw/9pfs: fix error handing in local_ioc_getversion())

[Michael S. Tsirkin]

On Thu, Feb 06, 2014 at 06:28:32PM +0530, Aneesh Kumar K.V wrote:
> "Michael S. Tsirkin" <address@hidden> writes:
> 
> > On Tue, Feb 04, 2014 at 12:51:25PM +0530, Aneesh Kumar K.V wrote:
> >> "Michael S. Tsirkin" <address@hidden> writes:
> >> 
> >> > On Mon, Feb 03, 2014 at 03:05:10PM +0530, Aneesh Kumar K.V wrote:
> >> >> "Michael S. Tsirkin" <address@hidden> writes:
> >> >> 
> >> >> > Haven't used 9pfs in a while.
> >> >> > I thought these patches are a good time to play with it some more.
> >> >> > I have encountered two issues.
> >> >> >
> >> >> > What I'm doing:
> >> >> > host: qemu a75143eda2ddf581b51e96c000974bcdfe2cbd10.
> >> >> >
> >> >> > /scm/qemu/x86_64-softmmu/qemu-system-x86_64 -enable-kvm -m 1g -cpu 
> >> >> > kvm64
> >> >> > -smp 2  f20-x64.qcow2  -netdev user,id=foo -redir tcp:8022::22 -device
> >> >> > virtio-net,netdev=foo  -serial stdio -fsdev
> >> >> > local,security_model=none,id=fsdev0,path=/lib/modules/ -device
> >> >> > virtio-9p-pci,id=fs0,fsdev=fsdev0,mount_tag=libmodulesshare -fsdev
> >> >> > local,security_model=none,id=fsdev1,path=/boot -device
> >> >> > virtio-9p-pci,id=fs1,fsdev=fsdev0,mount_tag=bootshare -no-reboot
> >> >> > -snapshot
> >> >> >
> >> >> > guest: Fedora 20
> >> >> >
> >> >> > added this in /etc/fstab:
> >> >> >
> >> >> > bootshare       /share/boot     9p      trans=virtio,version=9p2000.L 
> >> >> > 0 0
> >> >> > libmodulesshare /share/lib/modules      9p 
> >> >> > trans=virtio,version=9p2000.L 0 0
> >> >> >
> >> >> >
> >> >> > I have encountered two issues:
> >> >> >
> >> >> > 1. mount failure on boot
> >> >> > If I try to mount on boot through fstab, I get:
> >> >> > [    2.270157] 9pnet: Could not find request transport: virtio
> >> >> > [    2.270158] 9pnet: Could not find request transport: virtio
> >> >> 
> >> >> 
> >> >> Missing 9pnet_virtio.ko module ? 
> >> >
> >> > Maybe it's loaded too late. But when I get to plymouth prompt
> >> > it's loaded fine.
> >
> > Any idea about this one? Do you have guests with 9pfs
> > and virtio as modules and 9pfs mounted from /etc/fstab?
> 
> No, I generally have everything builtin for guest. 

Heh that's the problem then :)
Try making it modular and I think you will see the problem.

> >
> >> >> >
> >> >> > If I then re-try mount, it succeeds immediately!
> >> >> >
> >> >> > Some kind of dependency issue?
> >> >> >
> >> >> > 2. files immediately in the mounted directory aren't visible on the
> >> >> > guest under /share/boot.
> >> >> > For example, files under /boot on host are not visible
> >> >> > on guest, files under child directories seem visible.
> >> >> 
> >> >> 
> >> >> can you share more details on this ? /boot permissions. ls -al output on
> >> >> host etc.
> >> >> 
> >> >> -aneesh
> >> >
> >> > for /boot:
> >> > dr-xr-xr-x. 7 root root 12288 Feb  2 23:41 /boot/
> >> >
> >> > $ ls -la
> >> > total 739740
> >> > dr-xr-xr-x.  7 root root    12288 Feb  2 23:41 .
> >> > dr-xr-xr-x. 22 root root     4096 Feb  2 19:16 ..
> >> > -rw-r--r--.  1 root root   138741 Dec 23 19:19 
> >> > config-3.12.6-200.fc19.i686
> >> > -rw-r--r--.  1 root root   138724 Jan 10 18:06 
> >> > config-3.12.7-200.fc19.i686
> >> > -rw-r--r--.  1 root root   138724 Jan 16 06:43
> >> > config-3.12.8-200.fc19.i686
> >> 
> >> 
> >> Related to SELinux errors ? can you double check you don't selinux
> >> errors.
> >
> > No, I didn't see any selinux errors.
> > Also was able to stat and read files as a regular user.
> >
> >> Can you also share the file listing on the guest ?
> >
> > Interestingly, the problem seems to be partially gone.
> > Not sure what did I change
> > What I do still see now is this:
> >
> > Host:
> > $ ls -l /boot/initramfs-3.11.0-rc5-mst.img
> > -rw-------. 1 root root 7659204 Aug 18 13:21 
> > /boot/initramfs-3.11.0-rc5-mst.img
> > Guest:
> > ls -l /share/initramfs-3.11.0-rc5-mst.img 
> > ls: cannot access /share/initramfs-3.11.0-rc5-mst.img: Permission denied
> >
> >
> 
> So you are able to stat the file as the same user the qemu is running
> ?. That is strange. I am not able to reproduce the problem. You could
> possibly instrument the virtio-9p-local.c and see the exact error ?
> 
> -aneesh

Sure, send me debug patch I'll apply and try it.

-- 
MST