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>,
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Saravana Kannan <saravanak@google.com>,
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Viresh Kumar <viresh.kumar@linaro.org>,
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Adrian Hunter <adrian.hunter@intel.com>,
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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.
next prev parent 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 [PATCH v2 0/3] iommu: Enable non-strict DMA on QCom SD/MMC 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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