[Xen-users] Got permission denied error when calling xenbus_printf function in the frontend driver

[Jintack Lim <jintack@xxxxxxxxxxxxxxx>]

Hi,

I was writing a simple backend/frontend driver,

and when I ran it, I got this error in dmesg.

"failed to write error node for device/vsimple/0 (13 writing ring-ref)"

The way I call xenbus_printf is pretty much the same as other drivers.

I calledÂxenbus_transaction_start before this line.

err = xenbus_printf(xbt, dev->nodename,

               Â"ring-ref", "%u", info->ring_ref);

I'm working on Xen 4.5.0, ARM64 architecture.

I referred this page, and used the same script at the bottom.

http://wiki.xenproject.org/wiki/Introduction_to_Xen_3.x#Adding_new_device_and_triggering_the_probe.28.29_functions

What could go wrong with permissions?

This is how my device (vsimple) looks like in Xenstore

after I ran the script above.

# xenstore-ls -p /local/domain/7/device

...

vsimple = "" . . . . . . . . . . . . . . . . . . . . . . . . Â(n0,r7)

Â0 = "" Â. . . . . . . . . . . . . . . . . . . . . . . . . . Â(n0,r7)

 backend-id = "0" . . . . . . . . . . . . . . . . . . . . . Â(n0,r7)

 backend = "/local/domain/0/backend/vsimple/7/0" Â. . . . . Â(n0,r7)

 state = "1" Â. . . . . . . . . . . . . . . . . . . . . . . Â(n0,r7)

The owner of vsimple is dom0, and domU only has the read permission.

It's somewhat obvious that I got the permission error..

The question is how can I fix this?

I also got errors related to writing new state, and domU is only allowed to read it as shown above again.

Thanks,

Jintack

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxx
http://lists.xen.org/xen-users