linux-kernel - [PATCH 0/6] iommu: Enable devices to request non-strict DMA, starting with QCom SD/MMC

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Date:   Mon, 21 Jun 2021 16:52:42 -0700
From:   Douglas Anderson <dianders@...omium.org>
To:     gregkh@...uxfoundation.org, rafael@...nel.org,
        rafael.j.wysocki@...el.com, will@...nel.org, robin.murphy@....com,
        joro@...tes.org, bjorn.andersson@...aro.org,
        ulf.hansson@...aro.org, adrian.hunter@...el.com,
        bhelgaas@...gle.com
Cc:     robdclark@...omium.org, linux-arm-msm@...r.kernel.org,
        linux-pci@...r.kernel.org, quic_c_gdjako@...cinc.com,
        iommu@...ts.linux-foundation.org, sonnyrao@...omium.org,
        saiprakash.ranjan@...eaurora.org, linux-mmc@...r.kernel.org,
        vbadigan@...eaurora.org, rajatja@...gle.com, saravanak@...gle.com,
        joel@...lfernandes.org, Douglas Anderson <dianders@...omium.org>,
        Andy Gross <agross@...nel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 0/6] iommu: Enable devices to request non-strict DMA, starting with QCom SD/MMC

This patch attempts to put forward a proposal for enabling non-strict
DMA on a device-by-device basis. The patch series requests non-strict
DMA for the Qualcomm SDHCI controller as a first device to enable,
getting a nice bump in performance with what's believed to be a very
small drop in security / safety (see the patch for the full argument).

As part of this patch series I am end up slightly cleaning up some of
the interactions between the PCI subsystem and the IOMMU subsystem but
I don't go all the way to fully remove all the tentacles. Specifically
this patch series only concerns itself with a single aspect: strict
vs. non-strict mode for the IOMMU. I'm hoping that this will be easier
to talk about / reason about for more subsystems compared to overall
deciding what it means for a device to be "external" or "untrusted".

If something like this patch series ends up being landable, it will
undoubtedly need coordination between many maintainers to land. I
believe it's fully bisectable but later patches in the series
definitely depend on earlier ones. Sorry for the long CC list. :(

Douglas Anderson (6):
  drivers: base: Add the concept of "pre_probe" to drivers
  drivers: base: Add bits to struct device to control iommu strictness
  PCI: Indicate that we want to force strict DMA for untrusted devices
  iommu: Combine device strictness requests with the global default
  iommu: Stop reaching into PCIe devices to decide strict vs. non-strict
  mmc: sdhci-msm: Request non-strict IOMMU mode

 drivers/base/dd.c             | 10 +++++--
 drivers/iommu/dma-iommu.c     |  2 +-
 drivers/iommu/iommu.c         | 56 +++++++++++++++++++++++++++--------
 drivers/mmc/host/sdhci-msm.c  |  8 +++++
 drivers/pci/probe.c           |  4 ++-
 include/linux/device.h        | 11 +++++++
 include/linux/device/driver.h |  9 ++++++
 include/linux/iommu.h         |  2 ++
 8 files changed, 85 insertions(+), 17 deletions(-)

-- 
2.32.0.288.g62a8d224e6-goog