Re: [PATCH 4/6] libxl: Use the block-tap script for LIBXL_DISK_BACKEND_TAP

[Wei Liu <wei.liu2@citrix.com>]

On Mon, Jul 06, 2015 at 11:51:41AM +0100, George Dunlap wrote:
> The block-tap script can now do everything needed for libxl; no need
> to link against the blktap library.
> 
> To do this:
> 
> * Set disk->script to "block-tap" and dev to "format:pdev_path" in
>   device_disk_add for LIBXL_DISK_BACKEND_TAP
> 
> * Remove libxl_blktap2.o and libxl_noblktap2.o and all code depending
>   on them
> 
> Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>
> ---
> CC: Ian Campbell <ian.campbell@citrix.com>
> CC: Ian Jackson <ian.jackson@citrix.com>
> CC: Wei Liu <wei.liu2@citrix.com>
> CC: Dave Scott <Dave.Scott@eu.citrix.com>
> CC: Jonathan Ludlam <Jonathan.Ludlam@eu.citrix.com>
> CC: Wen Congyang <wency@cn.fujitsu.com>
> CC: Yang Hongyang <yanghy@cn.fujitsu.com>
> CC: Felipe Franciosi <felipe.franciosi@citrix.com>
> 
> Note: This is broken for HVM domains at the moment because all block
> scripts are broken for HVM domains.  That is a bug which should be a
> blocker for the 4.6 release.  As such, I think there is justification

This bug is partially fixed by this particular patch. I think making
things partially work is better than having it not work at all.

> for checking in this "feature" (enabling use of a 'system' blktap)
> with the assumption that the FIXME will go away before the release.
> 

I have the impression that to make QEMU work with block script (the
FIXME) would require us to devise a way to get back the path of block
device node. Am I right? How much work do you envisage is needed to make
that FIXME go away?

On the flip side we're not making anything worse than before so we can
probably get by by writing that down in known issues section of release
note.

Wei.