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[Xen-devel] Re: [Patch 3/3] New blktap implementation

To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Subject: [Xen-devel] Re: [Patch 3/3] New blktap implementation
From: Gerd Hoffmann <kraxel@xxxxxxxxxx>
Date: Tue, 04 Nov 2008 11:43:59 +0100
Cc: Dutch Meyer <dmeyer@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, "andrew.warfield@xxxxxxxxxx" <andrew.warfield@xxxxxxxxxx>
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Keir Fraser wrote:
> On 31/10/08 03:16, "Dutch Meyer" <dmeyer@xxxxxxxxx> wrote:
> 
>>    3) A kernel patch to add a new unified blktap2 module that will
>> eventually replace blktap.
> 
> Is it necessary to keep old blktap kernel driver around for qemu's tap
> implementation? Can the two drivers (old and new) coexist next to each
> other?

They don't conflict all all, they can coesist exactly like blkback and
blktap can coexist today.  The qemu implementation uses another backend
directory (blkback is 'vbd', blktap is 'tap', qemu is 'qdisk').

To be usable qdisk will need some windup in xend, so it either creates
the xenstore entries needed or adds the approximate command line options
when starting qemu-dm.

So one can do a smooth switchover: (a) wait for it being merged, (b) do
xend windup and test stuff, (c) fix bug if needed and (d) drop blktap
once we are confident there are no regressions.

cheers,
  Gerd



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