RE: [Xen-devel] XEN 4.0.2-rc2 - using OCAML xenstored -- xend not starting?

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2011-02-10 at 17:53 +0000, Yuvraj Agarwal wrote: 
> Hi Ian and Vincent,
> 
> Thank you for your responses - There are several possible issues it seems:

No, just one -- the event channel one. 

> ** I actually have both /dev/xen/eventchn and /dev/xen/evtchn
> but no /dev/xen/gntdev currently?

AFAIK oxenstored does not use gntdev.

> root@EM:/home/yuvraj#
> 
> ** It also looks like the minor numbers are mixed up, for example /proc/misc 
> shows minor number 63 also for vga_arbitrer? Not sure if that matters.

The misc device minor numbers are completely dynamic so becoming "mixed
up" is normal. The bug is that this version of oxenstored hardcodes a
specific minor number, which is wrong.

It also uses the device name /dev/xen/eventchn which is different to
the /dev/xen/evtchn that the system creates, but that's a minor aside.

> root@EM:/home/yuvraj# cat /proc/misc
> < snip >
> 59 gntdev
> 60 evtchn
> < snip >
> 63 vga_arbiter
> root@EM:/home/yuvraj#
[...] 
> root@EM:/home/yuvraj# strace -f /usr/bin/xenstored --no-fork
> 
> <snip>
> open("/dev/xen/eventchn", O_RDWR)       = 6

So here you open /dev/xen/eventchn, which oxenstored created as 10:63.
But, as shown in /proc/misc above, the event channel driver actually
ends up with minor 60 on this kernel and so the device you have just
opened is the vga_arbiter, whatever that is.

Hence... 

> ioctl(6, EVIOCGVERSION, 0x7fffd0cd3e30) = -1 ENOTTY (Inappropriate ioctl for 
> device)

... this fails, since that ioctl is not valid for the vga_arbiter.

> Is there a way I can fix (e.g. a patch I can apply) this on my end?

Yes. Apply the patch I linked to in my previous mail (e.g.
http://xenbits.xensource.com/xen-unstable.hg?rev/e7b55cc5533a) to the
tree under tools/ocaml-xenstored. You may need to adjust the paths in
the (hopefully) obvious way.

This patch causes oxenstored to use the exiting evtchn device node which
is correctly created by udev with the correct minor number.

Ian.



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