netdev - Re: [PATCH v2] ARM: net: JIT compiler for packet filters

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Date:	Mon, 19 Dec 2011 19:14:01 +0200
From:	Mircea Gherzan <mgherzan@...il.com>
To:	Dave Martin <dave.martin@...aro.org>
Cc:	linux-arm-kernel@...ts.infradead.org, netdev@...r.kernel.org
Subject: Re: [PATCH v2] ARM: net: JIT compiler for packet filters

Hi,

On Mon, Dec 19, 2011 at 03:52:52PM +0000, Dave Martin wrote:
> On Mon, Dec 19, 2011 at 04:33:38PM +0100, Uwe Kleine-K?nig wrote:
> > Hello,
> > 
> > On Mon, Dec 19, 2011 at 03:24:18PM +0000, Dave Martin wrote:
> > > On Mon, Dec 19, 2011 at 04:19:58PM +0100, Uwe Kleine-K?nig wrote:
> > > > On Mon, Dec 19, 2011 at 12:50:21PM +0000, Dave Martin wrote:
> > > > > On Mon, Dec 19, 2011 at 09:40:30AM +0100, Mircea Gherzan wrote:
> > > > > > Based of Matt Evans's PPC64 implementation.
> > > > > Note that it's fine to have the JIT generating ARM code, even if the rest
> > > > > if the kernel is Thumb-2.  This would only start to cause problems if we
> > > > > want to do things like set kprobes in the JITted code, or unwind out of
> > > > > the JITted code.
> > > > or use a CPU that doesn't speak ARM (e.g. v7M)
> > > 
> > > Indeed... I was assuming though that that would be out of scope for the
> > > first iteration of this code.
> > Right, depending on !THUMB2 is fine. Only generating ARM code with
> > THUMB2=y is not.
> 
> The kernel doesn't support v7-M upstream though.  CONFIG_THUMB2_KERNEL=y
> doesn't mean that there is no ARM code present -- there _is_ ARM code in
> the kernel image even with this option (though not very much).

What about relying at runtime on bits[3:0] of ID_PFR0? And this only for
ARMv7.

Are there any other ARM cores of interest that do _not_ support the ARM
instruction set?

Thanks,
Mircea
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