From: Rajat Jain <rajatja@google.com>
To: Doug Anderson <dianders@chromium.org>
Cc: 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>,
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Thierry Reding <thierry.reding@gmail.com>,
Joel Fernandes <joel@joelfernandes.org>,
Will Deacon <will@kernel.org>, Rob Clark <robdclark@chromium.org>,
Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>,
Saravana Kannan <saravanak@google.com>,
Jonathan Corbet <corbet@lwn.net>, Joerg Roedel <joro@8bytes.org>,
quic_c_gdjako@quicinc.com,
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Viresh Kumar <viresh.kumar@linaro.org>,
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"list@263.net:IOMMU DRIVERS" <iommu@lists.linux-foundation.org>,
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Robin Murphy <robin.murphy@arm.com>,
"Maciej W. Rozycki" <macro@orcam.me.uk>
Subject: Re: [PATCH v2 0/3] iommu: Enable non-strict DMA on QCom SD/MMC
Date: Mon, 2 Aug 2021 17:09:08 -0700 [thread overview]
Message-ID: <CACK8Z6FV+QYR01=aP4AT8rNUQMkX-WwesHzf5XY8465KuUZ=_Q@mail.gmail.com> (raw)
In-Reply-To: <CAD=FV=XaTqNDn=vLEXfJ2dV+EH2UoxPfzWeiS+_sZ9hrQ274bw@mail.gmail.com>
Hi Robin, Doug,
On Wed, Jul 14, 2021 at 8:14 AM Doug Anderson <dianders@chromium.org> wrote:
>
> Hi,
>
> On Tue, Jul 13, 2021 at 11:07 AM Robin Murphy <robin.murphy@arm.com> wrote:
> >
> > On 2021-07-08 15:36, Doug Anderson wrote:
> > [...]
> > >> Or document for the users that want performance how to
> > >> change the setting, so that they can decide.
> > >
> > > Pushing this to the users can make sense for a Linux distribution but
> > > probably less sense for an embedded platform. So I'm happy to make
> > > some way for a user to override this (like via kernel command line),
> > > but I also strongly believe there should be a default that users don't
> > > have to futz with that we think is correct.
> >
> > FYI I did make progress on the "punt it to userspace" approach. I'm not
> > posting it even as an RFC yet because I still need to set up a machine
> > to try actually testing any of it (it's almost certainly broken
> > somewhere), but in the end it comes out looking surprisingly not too bad
> > overall. If you're curious to take a look in the meantime I put it here:
> >
> > https://gitlab.arm.com/linux-arm/linux-rm/-/commits/iommu/fq
I was wondering if you got any closer to testing / sending it out? I
looked at the patches and am trying to understand, would they also
make it possible to convert at runtime, an existing "non-strict"
domain (for a particular device) into a "strict" domain leaving the
other devices/domains as-is? Please let me know when you think your
patches are good to be tested, and I'd also be interested in trying
them out.
>
> Being able to change this at runtime through sysfs sounds great and it
> fills all the needs I'm aware of, thanks! In Chrome OS we can just use
> this with some udev rules and get everything we need.
I still have another (inverse) use case where this does not work:
We have an Intel chromebook with the default domain type being
non-strict. There is an LTE modem (an internal PCI device which cannot
be marked external), which we'd like to be treated as a "Strict" DMA
domain.
Do I understand it right that using Rob's patches, I could potentially
switch the domain to "strict" *after* booting (since we don't use
initramfs), but by that time, the driver might have already attached
to the modem device (using "non-strict" domain), and thus the damage
may have already been done? So perhaps we still need a device property
that the firmware could use to indicate "strictness" for certain
devices at boot?
Thanks,
Rajat
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next prev parent reply other threads:[~2021-08-03 0:13 UTC|newest]
Thread overview: 19+ 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 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 [this message]
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
2021-07-14 10:48 ` Joerg Roedel
2021-07-09 19:21 ` Robin Murphy
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