linux-kernel - Re: [Xen-devel] [PATCH] xen/p2m: Export set_phys_to

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Date:	Fri, 06 Sep 2013 15:49:13 +0100
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"Konrad Rzeszutek Wilk" <konrad.wilk@...cle.com>
Cc:	<david.vrabel@...rix.com>,
	"xen-devel" <xen-devel@...ts.xenproject.org>,
	<boris.ostrovsky@...cle.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH] xen/p2m: Export set_phys_to_machine.

>>> On 06.09.13 at 16:39, Konrad Rzeszutek Wilk <konrad.wilk@...cle.com> wrote:
> On Fri, Sep 06, 2013 at 03:06:02PM +0100, Jan Beulich wrote:
>> >>> On 06.09.13 at 16:00, Konrad Rzeszutek Wilk <konrad.wilk@...cle.com> wrote:
>> > We have already exported 'get_phys_to_machine' and there are
>> > third-party drivers that depend on this other symbol. As such
>> > lets make this balanced and also export this symbol.
>> 
>> I tend to disagree: Allowing external modules read access to some
>> internal state is quite different from also allowing them to alter it.
> 
> I am not following you. We have drivers in the kernel that do
> this now. For example xen-netfront uses set_phys_to_machine.

In which case exporting it would be fine (and necessary). But you
explicitly said "third-party drivers".

> Oddly it can be built as a module.  I am wondering how it actually
> works without this EXPORT symbol.

See the early return in xennet_release_rx_bufs() - the use of
the symbol is in dead code.

Jan

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