linux-kernel - Re: How to efficiently handle DMA and cache on ARMv7 ? (was "Is get_user_pages() enough to prevent pages from being swapped out ?")

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20090807131501.GD2763@sgi.com>
Date:	Fri, 7 Aug 2009 08:15:01 -0500
From:	Robin Holt <holt@....com>
To:	Laurent Desnogues <laurent.desnogues@...il.com>
Cc:	Jamie Lokier <jamie@...reable.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	David Xiao <dxiao@...adcom.com>,
	Ben Dooks <ben-linux@...ff.org>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Robin Holt <holt@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	v4l2_linux <linux-media@...r.kernel.org>,
	"linux-arm-kernel@...ts.arm.linux.org.uk" 
	<linux-arm-kernel@...ts.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 ?")

On Fri, Aug 07, 2009 at 02:07:43PM +0200, Laurent Desnogues wrote:
> On Fri, Aug 7, 2009 at 11:54 AM, Jamie Lokier<jamie@...reable.org> wrote:
> >
> > 1. Does the architecture not prevent speculative instruction
> > prefetches from crossing a page boundary?  It would be handy under the
> > circumstances.
> 
> There's no such restriction in ARMv7 architecture.

Doesn't it prevent them for uncached areas?  I _THOUGHT_ there was an
alloc_consistent (or something like that) call on ARM which gave you
an uncached mapping where you could do DMA.  I also thought there was
a dma_* set of functions which remapped as uncached before DMA begins
and remapped as normal after DMA has been completed.

Sorry for the fuzzy recollection.  I am dredging from 2.6.21 timeframe.

Robin
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/