linux-kernel - Re: [Linaro-mm-sig] [RFC v2 1/2] dma-buf: Introduce dma buffer sharing mechanism

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 for Android: free password hash cracker in your pocket

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

Message-Id: <201112201541.17904.arnd@arndb.de>
Date:	Tue, 20 Dec 2011 15:41:17 +0000
From:	Arnd Bergmann <arnd@...db.de>
To:	"Semwal, Sumit" <sumit.semwal@...com>
Cc:	Daniel Vetter <daniel@...ll.ch>,
	Alan Cox <alan@...rguk.ukuu.org.uk>, linux@....linux.org.uk,
	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	linaro-mm-sig@...ts.linaro.org, linux-mm@...ck.org,
	linux-media@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [Linaro-mm-sig] [RFC v2 1/2] dma-buf: Introduce dma buffer sharing mechanism

On Monday 19 December 2011, Semwal, Sumit wrote:
> I didn't see a consensus on whether dma_buf should enforce some form
> of serialization within the API - so atleast for v1 of dma-buf, I
> propose to 'not' impose a restriction, and we can tackle it (add new
> ops or enforce as design?) whenever we see the first need of it - will
> that be ok? [I am bending towards the thought that it is a problem to
> solve at a bigger platform than dma_buf.]

The problem is generally understood for streaming mappings with a 
single device using it: if you have a long-running mapping, you have
to use dma_sync_*. This obviously falls apart if you have multiple
devices and no serialization between the accesses.

If you don't want serialization, that implies that we cannot have
use the  dma_sync_* API on the buffer, which in turn implies that
we cannot have streaming mappings. I think that's ok, but then
you have to bring back the mmap API on the buffer if you want to
allow any driver to provide an mmap function for a shared buffer.

	Arnd
--
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/