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Re: [Xen-devel] [PATCH, v2] add privileged/unprivileged kernel feature i

To: Jan Beulich <JBeulich@xxxxxxxxxx>, Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH, v2] add privileged/unprivileged kernel feature indication
From: Keir Fraser <keir@xxxxxxx>
Date: Thu, 21 Jul 2011 10:10:14 +0100
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On 21/07/2011 10:01, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:

>> My own issue with the unprivileged flag is that I'm not clear what it
>> actually means. When would you *not* set it? I mean it looks in the Linux
>> side you set it unconditionally right now. What's the point? Why not remove
>> the flag and introduce it when we have good reason and can attach meaningful
>> semantics to it?
> 
> Again - you're talking about an actual guest side implementation (which,
> in this particular case, has to honor how the rest of the implementation
> is done, i.e. it has to set the flag unconditionally). I'm talking about an
> abstract interface definition that should suit everyone (existing as well
> as yet to come).

I'm afraid my view is that !dom0 operation is a mode that every PV guest is
capable of -- that's the definition of what a PV guest is, to my mind!

Like I said in my other email, pinning it down more precisely -- e.g., must
have PV drivers -- will have counterexamples.

I don't know though --- maybe a distro could have dom0 and domU separate
kernel builds, and want to set the flags differently for each. I wonder how
much of a long shot that use case is.

 -- Keir



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