Re: [gentoo-user] gentoo-sources and xen blktap driver?

[Pandu Poluan]

On Jan 8, 2012 12:43 AM, "Michael Mol" <mikemol@×××××.com> wrote:
>
> On Sat, Jan 7, 2012 at 11:35 AM, Pandu Poluan <pandu@××××××.info> wrote:
> > On Jan 7, 2012 8:44 PM, "victor romanchuk" <rom@××××××××××.net> wrote:
> >>
> >> Konstantinos Agouros wrote, at 01/07/2012 03:51 PM:
> >> > since xen got into the mainstream kernel the way to go is to use
> >> > gentoo-sources for dom0 and the domUs. However the blktap modules are
> >> > not
> >> > there. Is there any way to get this to work?
> >>
> >> blktap drivers were excluded from kernel mainline since 3.x, these two
> >> threads
> >> from xen-users mailing list might put some light in that context:
> >>
> >>
> >>
http://old-list-archives.xen.org/archives/html/xen-users/2011-07/msg00637.html
> >>
> >>
http://old-list-archives.xen.org/archives/html/xen-users/2011-10/msg00065.html
> >>
> >> the latest sys-kernel/xen-sources containing working blktap (not
blktap2)
> >> is
> >> 2.6.38 (this is buggy from my point of view; i'm still sitting on
> >> 2.6.34-r5 for
> >> production installations)
> >>
> >
> > Can someone shed a light on the importance of blktap, i.e., why one
would
> > want to use it when -- as someone explained in the first email thread
you
> > gave -- blkfront+blkend is enough for paravirtualization?
>
> Reading through the linked threads, it sounds like the benefit stems
> from being able to shim things in between the front and back ends.
>
> You might want that for any number of reasons:
> * a block encryption layer
> * a metering layer
> * a read/write masking layer
> * an intercept to have the block device exist on (or be mirrored to)
> on another system.
>
> etc.
>

Ah yes, of course.

One of the threads also mentioned that blktap might be better implemented
in userspace.

Rgds,