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From: Joerg Roedel <joro@8bytes.org>
To: Robin Murphy <robin.murphy@arm.com>
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 12:15:20 +0200	[thread overview]
Message-ID: <YO65OOScL5vru1Kr@8bytes.org> (raw)
In-Reply-To: <edd1de35-5b9e-b679-9428-23c6d5005740@arm.com>

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

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.

Regards,

	Joerg


  reply	other threads:[~2021-07-14 10:15 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 [this message]
2021-07-14 10:29             ` Robin Murphy
2021-07-14 10:48               ` Joerg Roedel
2021-07-09 19:21         ` Robin Murphy

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