linux-kernel - Re: [RFC] dma: passing "attributes" to dma_map

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] [day] [month] [year] [list]

Message-Id: <1198272690.6737.21.camel@pasglop>
Date:	Sat, 22 Dec 2007 08:31:30 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	akepner@....com
Cc:	Stefan Richter <stefanr@...6.in-berlin.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	grundler@...isc-linux.org, jbarnes@...tuousgeek.org, jes@....com,
	randy.dunlap@...cle.com, rdreier@...co.com,
	James.Bottomley@...eleye.com, davem@...emloft.net,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC] dma: passing "attributes" to dma_map_* routines


On Fri, 2007-12-21 at 10:00 -0800, akepner@....com wrote:
> On Fri, Dec 21, 2007 at 07:56:25AM +1100, Benjamin Herrenschmidt wrote:
> > ...
> > Can't you just have a primitive to sync things up that you call
> > explicitely from your driver after fetching a new status entry ?
> > 
> 
> Well, the only mechanisms I know to get things synced are the ones 
> I mentioned before: 1) generate an interrupt, 2) write to memory 
> which has the "barrier" attribute. Obviously 1 is out - giving  
> the memory used for status indications the barrier attribute is 
> the most primitive means I'm aware of.

Well, I'm not totally against turning "direction" into a flag mask, as I
do have requests to do something similar on some PowerPC's in fact in
order to control the ordering guarantees of a given DMA mapping (ie.
relaxed vs. fully ordered).

I'm just worried that we'll end up with as many semantics for those
flags as we have host bridges & archs around, which would be bad.

Ben.


--
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/