linux-kernel - Re: [PATCH RFC 1/8] arm: make SWIOTLB available

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: <20130802121340.GH24540@konrad-lan.dumpdata.com>
Date:	Fri, 2 Aug 2013 08:13:40 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc:	xen-devel@...ts.xensource.com, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, Ian.Campbell@...rix.com,
	will.deacon@....com, linux@....linux.org.uk
Subject: Re: [PATCH RFC 1/8] arm: make SWIOTLB available

On Fri, Aug 02, 2013 at 12:59:00PM +0100, Stefano Stabellini wrote:
> On Wed, 31 Jul 2013, Konrad Rzeszutek Wilk wrote:
> > Stefano Stabellini <stefano.stabellini@...citrix.com> wrote:
> > >Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
> > >CC: will.deacon@....com
> > >CC: linux@....linux.org.uk
> > >---
> > > arch/arm/Kconfig                   |    7 +++++++
> > > arch/arm/include/asm/dma-mapping.h |   24 ++++++++++++++++++++++++
> > > 2 files changed, 31 insertions(+), 0 deletions(-)
> > >
> > >diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> > >index ba412e0..05125ab 100644
> > >--- a/arch/arm/Kconfig
> > >+++ b/arch/arm/Kconfig
> > >@@ -1832,6 +1832,13 @@ config CC_STACKPROTECTOR
> > > 	  neutralized via a kernel panic.
> > > 	  This feature requires gcc version 4.2 or above.
> > > 
> > >+config SWIOTLB
> > >+	def_bool y
> > >+	select NEED_SG_DMA_LENGTH
> > >+
> > >+config IOMMU_HELPER
> > >+	def_bool SWIOTLB
> > >+
> > 
> > Could you explain the purpose of these two a bit more please? 
> 
> SWIOTLB is not available on arm at the moment.
> We need to make it available, otherwise SWIOTLB_XEN won't be able to
> select it.
> 
> Similarly, IOMMU_HELPER is another lib Kconfig symbol needed by SWIOTLB
> to compile.

I was more curious about the NEED_SG_DMA_LENGTH and IOMMU_HELPER.
I think the NEED_SG_DMA_LENGTH is optional? Or does SWIOTLB complain
about? I do recall seeing a patch for this at some point but it was
malformed. It was just changing SWIOTLB to use a macro for
sg->dma_length or such.

But the IOMMU_HELPER? That seems odds as the DMA API (which as you know
is what SWIOTLB hooks up to) is _below_ the IOMMU API.  Ah, it is 
'iommu_is_span_boundary' function.  Gotcha.

Could you mention that in the git commit please? Just say that SWIOTLB
uses some of the common code that IOMMU API uses - which is in the
lib/iommu_helper.c hence the need for that.

And for the NEED_SG_DMA_LENGTH let me dig up the patch at some point and
send it your way so you can make it part of this series.


--
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/