Re: [Xen-devel] BLKTAPCTRL[2375]: blktapctrl_linux.c:86: blktap0 open failed

[Daniel Stodden <daniel.stodden@xxxxxxxxxx>]

On Thu, 2010-07-22 at 12:59 -0400, Dante Cinco wrote:
> Daniel,
> 
> My cfg has this: disk = [ 'tap:tapdisk:vhd:/mnt/win2008sp2.vhd,xvda:sda1,w' ]
> 
> If I remove tapdisk, I get this error:
> 
> Error: need more than 1 value to unpack
> 
> Here's a more basic question: How do I check if my dom0 kernel has
> blktap2? Is the presence of /dev/xen/blktap-2 (such as below) a
> necessary indicator?
> kaan-20:~# ls -l /dev/xen/blktap-2
> crw------- 1 root root 253,  0 Jul 21 20:29 blktap0
> crw------- 1 root root  10, 59 Jul 21 20:29 control
> brw------- 1 root root 253,  0 Jul 21 20:29 tapdev0

No. These will be generated by udev in the future, in which case this
would be indication, too. But right now the toolstack mknods them if
they don't exist.

You should see a /sys/class/blktap2 directory and 'tapdev' and 'blktap2'
device entries in /proc/devices.

> The system with Xen 4.0.1-rc4 and 2.6.32.16 where VHD does not work
> does not have any blktap in /dev/xen:
> kaan-11:~# ls -l /dev/xen
> crw-rw---- 1 root root 10, 54 Jul 22 01:57 evtchn
> crw-rw---- 1 root root 10, 61 Jul 22 01:57 gntdev
> Does this mean this dom0 kernel does not have the blktap driver?
> 
> The kernel config file for the system where VHD does not work contains
> the following. Is this correct?
> CONFIG_XEN_BLKDEV_FRONTEND=m
> CONFIG_XEN_BLKDEV_BACKEND=y
> CONFIG_XEN_BLKDEV_TAP=y
> CONFIG_XEN_BLKBACK_PAGEMAP=y

Yep.

Problem is I'm not very good with xen-stable, as you might have already
guessed.

There's a lot of 'tap' vs. 'tap2' stuff in the python sources.

How about tap2:tapdisk:...?

:>

Daniel


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