linux-kernel - Re: [PATCH] [39/40] i386: Export paravirt

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Date:	Mon, 30 Apr 2007 14:30:47 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	Christoph Hellwig <hch@...radead.org>, Andi Kleen <ak@...e.de>,
	mingo@...e.hu, patches@...-64.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [39/40] i386: Export paravirt_ops for non GPL modules
 too

Alan Cox wrote:
> On Mon, 30 Apr 2007 11:50:09 +0100
> Christoph Hellwig <hch@...radead.org> wrote:
>
>   
>> On Mon, Apr 30, 2007 at 12:28:14PM +0200, Andi Kleen wrote:
>>     
>>> Otherwise non GPL modules cannot even do basic operations
>>> like disabling interrupts anymore, which would be excessive.
>>>
>>> Longer term should split the single structure up into
>>> internal and external symbols and not export the internal
>>> ones at all.
>>>
>>> Signed-off-by: Andi Kleen <ak@...e.de>
>>>       
>> Ingo was dead-set against this and I kinda agree. 
>>     
>
> Ditto - do the work first then merge it.
>   

The majority of paravirt_ops entrypoints are things which are currently
exported as inline functions in headers anyway.  There isn't a lot which
would become available to modules under a CONFIG_PARAVIRT kernel which
isn't already available to a non-CONFIG_PARAVIRT kernel.

We can hide the few remaining entries, I suppose.  But any module which
used them would only work with a PARAVIRT kernel anyway, so its hardly
going to be the best course for a module author - assuming they're at
all useful anyway (ooh, look, we can activate an mm!).

If we want to address this consistently, then we could scatter a pile of
#ifndef MODULEs around the headers to make sure the inlines are not
visible to modules in either case.  And we could correspondingly nobble
paravirt_ops by masking unexported entries with #ifndef MODULE.

So it isn't worth worrying about the paravirt_ops export unless you also
deal with the non-PARAVIRT case.

    J
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