linux-kernel - Re: [PATCH v2] x86: Remove compat vdso support

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Date:	Thu, 13 Mar 2014 17:23:25 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
cc:	Stefani Seibold <stefani@...bold.net>,
	Andy Lutomirski <luto@...capital.net>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	Dave Jones <davej@...hat.com>,
	Martin Runge <Martin.Runge@...de-schwarz.com>,
	Andreas Brief <Andreas.Brief@...de-schwarz.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v2] x86: Remove compat vdso support

On Wed, 12 Mar 2014, Linus Torvalds wrote:
> On Wed, Mar 12, 2014 at 8:46 AM, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
> >
> >  - do *not* add the HPET/VVAR page games to the legacy case. Get rid
> > of the remap_pfn_pages() games entirely.
> 
> .. actually, another approach would be to do the HPET/VVAR page games,
> but make them non-legacy.
> 
> The reason I hate seeing those remap_pfn_range() things is because
> it's nasty code for a legacy case that I think shouldn't have new code
> written for it, especially when it won't get testing by developers.
> 
> So my reaction was "don't do that".
> 
> But people pointing out that we can't do what x86-64 does made me
> think: we could avoid the whole "nasty code for a legacy case" by
> making it the *non*-legacy case. We could get rid of the fixmap
> HPET/VVAR entirely - on x86-64 (which can use those addresses) a
> PC-relative addressing is probably actually better anyway, so mapping
> them together with the vdso code shouldn't hurt.
> 
> That would remove my objections to doing all this stuff for a case
> that developers won't see and use (the whole "It's dead, Jim"
> objection) . And it would unify the 32-bit and 64-bit cases.
>
> Together with Andy's "remove legacy 32-bit fixmap vdso", I'd feel that
> this is actually an _improvement_ to the current situation.
> 
> Would something like that be more acceptable to everybody?

Definitely yes.

Thanks,

	tglx



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