From: Arnd Bergmann <arnd@arndb.de>
To: linux-arm-kernel@lists.infradead.org
Cc: Szabolcs Nagy <nsz@port70.net>, Rich Felker <dalias@libc.org>,
Russell King - ARM Linux <linux@arm.linux.org.uk>,
Kees Cook <keescook@chromium.org>,
Catalin Marinas <catalin.marinas@arm.com>,
"musl@lists.openwall.com" <musl@lists.openwall.com>,
Andy Lutomirski <luto@amacapital.net>
Subject: Re: ARM atomics overhaul for musl
Date: Mon, 17 Nov 2014 13:21:03 +0100 [thread overview]
Message-ID: <4211926.t6Cc7quoTR@wuerfel> (raw)
In-Reply-To: <20141117114832.GB29595@e104818-lin.cambridge.arm.com>
On Monday 17 November 2014 11:48:33 Catalin Marinas wrote:
> On Sun, Nov 16, 2014 at 04:33:56PM +0000, Russell King - ARM Linux wrote:
> > On Sun, Nov 16, 2014 at 12:56:56AM -0500, Rich Felker wrote:
> > > Aside from that, the only case among the above that's "right" already
> > > is v7+. Hard-coding the mcr-based barrier on v6 is wrong because it's
> >
> > I don't think it's wrong at all. The instruction isn't going away from
> > ARMv7, because ARMv7 deprecates it, but it _still_ has to be implemented
> > by a CPU conforming to ARMv7. As ARMv7 is going to be the last 32-bit
> > ARM architecture, we aren't going to see the MCR instruction disappearing
> > on 32-bit CPUs.
>
> You are wrong here. ARMv8-A supports 32-bit at all levels. ARMv8-R is
> 32-bit only (and it even has an MMU at EL1). And there is a slight
> chance that we may even see 32-bit only ARMv8-A implementations (I'm not
> really giving a hint and I'm not aware of any but I don't see anything
> preventing this, it's all marketing driven).
FWIW, both Samsung EXYNOS and Qualcomm Snapdragon SoCs based on Cortex-A53
have been shipped in 32-bit only devices.
Arnd
next prev parent reply other threads:[~2014-11-17 12:21 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-16 5:56 Rich Felker
2014-11-16 16:33 ` Russell King - ARM Linux
2014-11-16 16:50 ` Rich Felker
2014-11-16 17:10 ` Russell King - ARM Linux
2014-11-16 18:27 ` Andy Lutomirski
2014-11-16 18:56 ` Rich Felker
2014-11-16 19:02 ` Rich Felker
2014-11-17 13:54 ` Catalin Marinas
2014-11-17 14:11 ` Szabolcs Nagy
2014-11-17 14:47 ` Catalin Marinas
2014-11-17 14:39 ` Russell King - ARM Linux
2014-11-17 15:26 ` Catalin Marinas
2014-11-17 15:47 ` Russell King - ARM Linux
2014-11-17 16:19 ` Catalin Marinas
2014-11-17 16:53 ` Russell King - ARM Linux
2014-11-17 17:48 ` Catalin Marinas
2014-11-17 17:38 ` Andy Lutomirski
2014-11-18 10:56 ` Catalin Marinas
2014-11-18 18:14 ` Will Deacon
2014-11-18 18:24 ` Andy Lutomirski
2014-11-18 19:19 ` Russell King - ARM Linux
2014-11-19 18:32 ` Catalin Marinas
2014-11-17 11:48 ` Catalin Marinas
2014-11-17 12:21 ` Arnd Bergmann [this message]
2014-11-17 13:30 ` Szabolcs Nagy
2014-11-17 14:34 ` Catalin Marinas
2014-11-16 22:33 ` Jens Gustedt
2014-11-16 23:23 ` Rich Felker
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