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From: Robin Murphy <robin.murphy@arm.com>
To: Joerg Roedel <joro@8bytes.org>
Cc: Doug Anderson <dianders@chromium.org>,
	Ulf Hansson <ulf.hansson@linaro.org>,
	Linux Doc Mailing List <linux-doc@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	linux-pci@vger.kernel.org,
	Konrad Dybcio <konrad.dybcio@somainline.org>,
	Thierry Reding <thierry.reding@gmail.com>,
	Joel Fernandes <joel@joelfernandes.org>,
	Rajat Jain <rajatja@google.com>, Will Deacon <will@kernel.org>,
	Rob Clark <robdclark@chromium.org>,
	Saravana Kannan <saravanak@google.com>,
	Jonathan Corbet <corbet@lwn.net>,
	quic_c_gdjako@quicinc.com,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Viresh Kumar <viresh.kumar@linaro.org>,
	Veerabhadrarao Badiganti <vbadigan@codeaurora.org>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	linux-arm-msm <linux-arm-msm@vger.kernel.org>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Sonny Rao <sonnyrao@chromium.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	Randy Dunlap <rdunlap@infradead.org>,
	Linux MMC List <linux-mmc@vger.kernel.org>,
	Adrian Hunter <adrian.hunter@intel.com>,
	LKML <linux-kernel@vger.kernel.org>,
	"list@263.net:IOMMU DRIVERS" <iommu@lists.linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	"Maciej W. Rozycki" <macro@orcam.me.uk>
Subject: Re: [PATCH v2 0/3] iommu: Enable non-strict DMA on QCom SD/MMC
Date: Wed, 14 Jul 2021 11:29:08 +0100	[thread overview]
Message-ID: <255adda2-3b5f-b080-4da1-f3c5d5a4f7a6@arm.com> (raw)
In-Reply-To: <YO65OOScL5vru1Kr@8bytes.org>

On 2021-07-14 11:15, Joerg Roedel wrote:
> Hi Robin,
> 
> On Fri, Jul 09, 2021 at 02:56:47PM +0100, Robin Murphy wrote:
>> As I mentioned before, conceptually I think this very much belongs in sysfs
>> as a user decision. We essentially have 4 levels of "strictness":
>>
>> 1: DMA domain with bounce pages
>> 2: DMA domain
>> 3: DMA domain with flush queue
>> 4: Identity domain
> 
> Together with reasonable defaults (influenced by compile-time
> options) it seems to be a good thing to configure at runtime via
> sysfs.
> 
> We already have CONFIG_IOMMU_DEFAULT_PASSTHROUGH, which can probably be
> extended to be an option list:
> 
> 	- CONFIG_IOMMU_DEFAULT_PASSTHROUGH: Trusted devices are identity
> 					    mapped
> 
> 	- CONFIG_IOMMU_DEFAULT_DMA_STRICT: Trusted devices are DMA
> 					   mapped with strict flush
> 					   behavior on unmap
> 
> 	- CONFIG_IOMMU_DEFAULT_DMA_LAZY: Trusted devices are DMA mapped
> 					 with flush queues for performance

Indeed, I got focused on the sysfs angle, but rearranging the Kconfig 
default that way to match makes a lot of sense, and is another thing 
which should fall out really easily from my domain type rework, so I'll 
add that to my branch now before I forget again.

> Untrusted devices always get into the DMA domain with bounce pages by
> default.
> 
> The defaults can be changed at runtime via sysfs. We already have basic
> support for runtime switching of the default domain, so that can be
> re-used.

As mentioned yesterday, already done! I'm hoping to be able to post the 
patches next week after some testing :)

Cheers,
Robin.

  reply	other threads:[~2021-07-14 10:29 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-24 17:17 Douglas Anderson
2021-06-24 17:17 ` [PATCH v2 1/3] iommu: Add per-domain strictness and combine with the global default Douglas Anderson
2021-06-24 17:17 ` [PATCH v2 2/3] iommu/arm-smmu: Check for strictness after calling impl->init_context() Douglas Anderson
2021-06-24 17:17 ` [PATCH v2 3/3] mmc: sdhci-msm: Request non-strict IOMMU mode Douglas Anderson
2021-06-24 23:05   ` Doug Anderson
2021-06-25 13:18 ` [PATCH v2 0/3] iommu: Enable non-strict DMA on QCom SD/MMC Joerg Roedel
2021-06-25 14:42   ` Doug Anderson
2021-07-07 20:00     ` Doug Anderson
2021-07-08  8:08       ` Joerg Roedel
2021-07-08 14:36         ` Doug Anderson
2021-07-13 18:07           ` Robin Murphy
2021-07-14 15:14             ` Doug Anderson
2021-08-03  0:09               ` Rajat Jain
2021-08-03  0:34                 ` Rajat Jain
2021-08-03  8:19                 ` Robin Murphy
2021-07-09 13:56         ` Robin Murphy
2021-07-14 10:15           ` Joerg Roedel
2021-07-14 10:29             ` Robin Murphy [this message]
2021-07-14 10:48               ` Joerg Roedel
2021-07-09 19:21         ` Robin Murphy

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