linux-kernel - Re: [PATCH 6/9] crypto: ux500/cryp - Set DMA configuration though dma_slave

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]

Date:	Fri, 26 Apr 2013 13:46:46 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Lee Jones <lee.jones@...aro.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linus WALLEIJ <linus.walleij@...ricsson.com>,
	Herbert Xu <herbert@...dor.hengli.com.au>,
	"David S. Miller" <davem@...emloft.net>,
	Andreas Westin <andreas.westin@...ricsson.com>,
	"linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
	magnus.p.persson@...ricsson.com
Subject: Re: [PATCH 6/9] crypto: ux500/cryp - Set DMA configuration though
 dma_slave_config()

On Fri, Apr 26, 2013 at 10:28:39AM +0200, Linus Walleij wrote:
> On Thu, Apr 25, 2013 at 4:11 PM, Arnd Bergmann <arnd@...db.de> wrote:
> 
> > The dma engine driver must know the address in its dma space, while the
> > slave driver has it available in physical space. These two are often the
> > same, but there is no generic way to convert between the two, especially
> > if the dma engine resides behind an IOMMU.
> >
> > The best assumption we can make is that the dma engine driver knows
> > how to convert between the two. Interestingly the documentation for
> > dma_slave_config talks about "physical address", while the structure
> > itself uses a dma_addr_t. Linus Walleij introduced the structure in
> > c156d0a5b0 "DMAENGINE: generic slave channel control v3", so I assume
> > he can shed some light on what he was thinking. I assume the documentation
> > is right but the structure is not and should be converted to use
> > phys_add_t or resource_size_t.
> 
> OK I could cook a patch for that, but I think I need some input from
> Vinod and/or Russell on this.
the dma_slave_config is physical address that should be passed directly to the
controller. Obviosuly it should phys_addr_t :)

The mapping & unmapping of dma buffer (memcpy and memory buffer in this txn) is
required to be performed by the client driver. The dmanegine or dmaengine driver
will not do that for you...

This is true for slave usage and not for async case.
> 
> It does make sense to me that if anything knows how to map a physical
> address into the DMA address space it'll be the DMA engine.
> 
> However this rings a bell that there may be a possible relation to
> DMA-API, since that API syncs memory buffers to the DMA
> address space if there is some MMU inbetween the DMA and the
> (ordinary, non-device) memory.
> 
> So if we think one step ahead, assuming the DMAC is actually behind
> an MMU making it see the device in some other address than the
> physical (bus) space, where would the address be resolved?
> 
> Yours,
> Linus Walleij
--
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/