netdev - where are the memory barriers in net driver rx DMA operations?

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

Message-ID: <4C52ED8C.9070709@genband.com>
Date:	Fri, 30 Jul 2010 09:19:40 -0600
From:	Chris Friesen <chris.friesen@...band.com>
To:	netdev@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	davem@...emloft.net
Subject: where are the memory barriers in net driver rx DMA operations?

Documentation/DMA-API-HOWTO.txt says that memory barriers are still
required when accessing consistent mappings.  The example they give is
for reordering stores to consistent memory but I assume this also
applies to reordering loads.

However, I see many net drivers accessing the descriptor ring (in
consistent memory), checking the status bit for the buffer, then calling
dma_unmap_single() and accessing the data without any explicit memory
barrier.  Does the unmapping call act as a barrier in this case?

Thanks,

Chris

-- 
Chris Friesen
Software Developer
GENBAND
chris.friesen@...band.com
www.genband.com
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html