linux-kernel - Re: [PATCH] ARM: add get_user() support for 8 byte types

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Message-ID: <20121119151847.GB3296@intel.com>
Date:	Mon, 19 Nov 2012 17:18:47 +0200
From:	Ville Syrjälä <ville.syrjala@...ux.intel.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Arnd Bergmann <arnd@...db.de>, Rob Clark <rob.clark@...aro.org>,
	patches@...aro.org, linux-kernel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org, linux-omap@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Jamie Lokier <jamie@...reable.org>
Subject: Re: [PATCH] ARM: add get_user() support for 8 byte types

On Mon, Nov 19, 2012 at 02:48:06PM +0000, Russell King - ARM Linux wrote:
> On Mon, Nov 19, 2012 at 04:32:36PM +0200, Ville Syrjälä wrote:
> > On Thu, Nov 15, 2012 at 02:39:41PM +0000, Arnd Bergmann wrote:
> > > On Thursday 15 November 2012, Rob Clark wrote:
> > > > > I still haven't heard a conclusive argument why we need to use get_user()
> > > > > rather than copy_from_user() in the DRM code. Is this about a fast path
> > > > > where you want to shave off a few cycles for each call, or does this
> > > > > simplify the code structure, or something else?
> > > > 
> > > > well, it is mostly because it seemed like a good idea to first try to
> > > > solve the root issue, rather than having to fix things up in each
> > > > driver when someone from x86-world introduces a 64b get_user()..
> > > 
> > > As pointed out by hpa earlier, x86-32 doesn't have a 64b get_user
> > > either. I don't think we have a lot of drivers that are used only
> > > on 64-bit x86 and on 32-bit ARM but not on 32-bit x86.
> > 
> > Ouch. I didn't realize that x86-32 doesn't have it. All the systems
> > where I've run the new code are 64bit so I never noticed the problem.
> > 
> > I see there was a patch [1] posted a long time ago to implement 64bit
> > get_user() on x86-32. I wonder what happened to it?
> > 
> > [1] https://lkml.org/lkml/2004/4/20/96
> 
> Wonderful lkml.org after four "Negotiating SSL connection..." messages
> gives me under elinks...
<snip> 
> what a wonderful site... please choose another LKML archive, preferably
> one which works.  Thanks.

This one look like the same thing:
http://article.gmane.org/gmane.linux.kernel/198823

-- 
Ville Syrjälä
Intel OTC
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