From: Jamie Lokier <jamie@shareable.org>
To: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
David Xiao <dxiao@broadcom.com>, Ben Dooks <ben-linux@fluff.org>,
Hugh Dickins <hugh.dickins@tiscali.co.uk>,
Robin Holt <holt@sgi.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
v4l2_linux <linux-media@vger.kernel.org>,
"linux-arm-kernel@lists.arm.linux.org.uk"
<linux-arm-kernel@lists.arm.linux.org.uk>
Subject: Re: How to efficiently handle DMA and cache on ARMv7 ? (was "Is get_user_pages() enough to prevent pages from being swapped out ?")
Date: Fri, 7 Aug 2009 10:54:27 +0100 [thread overview]
Message-ID: <20090807095426.GI8725@shareable.org> (raw)
In-Reply-To: <20090807081041.GB18343@n2100.arm.linux.org.uk>
Russell King - ARM Linux wrote:
> On Fri, Aug 07, 2009 at 09:58:30AM +0200, Laurent Pinchart wrote:
> > Sorry about this, but I'm not sure to understand the speculative prefetching
> > cache issue completely.
>
> The general case with speculative prefetching is that if memory is
> accessible, it can be prefetched.
>
> In other words, if we mapped devices without NX (non-exec) set, the
> CPU can prefetch instructions from devices, causing random read
> accesses. Yes, I know it sounds crazy, but that's what I'm told
> _can_ happen.
1. Does the architecture not prevent speculative instruction
prefetches from crossing a page boundary? It would be handy under the
circumstances.
2. Is NX available on all the CPUs with speculative prefetching
behaviour? If it is, just use that for device mappings?
-- Jamie
next prev parent reply other threads:[~2009-08-07 9:54 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-08-06 10:08 How to efficiently handle DMA and cache on ARMv7 ? (was "Is get_user_pages() enough to prevent pages from being swapped out ?") Laurent Pinchart
2009-08-06 11:46 ` Ben Dooks
2009-08-06 13:06 ` Laurent Pinchart
2009-08-06 18:46 ` David Xiao
2009-08-06 19:16 ` Chetan.Loke
2009-08-06 20:15 ` Jamie Lokier
2009-08-06 22:25 ` Russell King - ARM Linux
2009-08-07 5:59 ` David Xiao
2009-08-07 7:58 ` Laurent Pinchart
2009-08-07 8:10 ` Russell King - ARM Linux
2009-08-07 9:54 ` Jamie Lokier [this message]
2009-08-07 9:59 ` Russell King - ARM Linux
2009-08-07 12:07 ` Laurent Desnogues
2009-08-07 13:15 ` Robin Holt
2009-08-07 19:01 ` Russell King - ARM Linux
2009-08-07 20:11 ` Laurent Pinchart
2009-08-07 20:28 ` Russell King - ARM Linux
2009-08-07 22:25 ` David Xiao
2009-08-10 13:49 ` Laurent Pinchart
2009-08-07 8:08 ` Russell King - ARM Linux
2009-08-07 10:23 ` Jamie Lokier
2009-08-07 19:03 ` Russell King - ARM Linux
2009-08-11 9:31 ` Catalin Marinas
2009-08-11 18:23 ` David Xiao
2009-08-07 7:48 ` Laurent Pinchart
2009-08-25 12:53 ` Steven Walter
2009-08-25 22:02 ` David Xiao
2009-08-25 23:17 ` Laurent Pinchart
2009-08-26 17:22 ` David Xiao
2009-09-01 13:31 ` Russell King - ARM Linux
2009-09-01 18:08 ` David Xiao
2009-09-01 13:28 ` Russell King - ARM Linux
2009-09-01 13:43 ` Laurent Pinchart
2009-09-01 14:18 ` Russell King - ARM Linux
2009-09-01 16:53 ` Hugh Dickins
2009-09-02 15:10 ` Imre Deak
2009-09-03 7:31 ` Imre Deak
2009-09-03 8:36 ` Russell King - ARM Linux
2009-09-08 13:05 ` Steven Walter
2009-08-07 7:29 ` Laurent Pinchart
2009-08-07 8:12 ` Matthieu CASTET
2009-08-07 10:13 ` How to efficiently handle DMA and cache on ARMv7 ? (was " Is " Laurent Pinchart
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