linux-kernel - Re: [Question] devm

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: <456e0515-b9d7-e1b6-fc25-a2ec5244d9db@metafoo.de>
Date:   Wed, 8 Mar 2017 21:44:17 +0100
From:   Lars-Peter Clausen <lars@...afoo.de>
To:     Russell King - ARM Linux <linux@...linux.org.uk>
Cc:     Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Robin Murphy <robin.murphy@....com>, dmaengine@...r.kernel.org,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Arnd Bergmann <arnd@...db.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
        Tejun Heo <tj@...nel.org>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [Question] devm_kmalloc() for DMA ?

On 03/08/2017 08:59 PM, Russell King - ARM Linux wrote:
> On Wed, Mar 08, 2017 at 08:48:31PM +0100, Lars-Peter Clausen wrote:
>> When the DMA memory is mapped for reading from the device the associated
>> cachelines are invalidated without writeback. There is no guarantee that
>> the changes made to the devres_node have made it to main memory yet, or
>> is there?
> 
> That is incorrect.
> 
> Overlapping cache lines are always written back on transitions from CPU
> to device ownership of the buffer (eg, dma_map_*().)

On ARM. But my understanding is that this is not a universal requirement
according to DMA-API.txt. It says that mappings must be cache line aligned
and otherwise behavior is undefined.