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

From: Douglas Anderson <dianders@chromium.org>
To: gregkh@linuxfoundation.org, rafael@kernel.org,
	rafael.j.wysocki@intel.com, will@kernel.org,
	robin.murphy@arm.com, joro@8bytes.org,
	bjorn.andersson@linaro.org, ulf.hansson@linaro.org,
	adrian.hunter@intel.com, bhelgaas@google.com
Cc: robdclark@chromium.org, linux-arm-msm@vger.kernel.org,
	linux-pci@vger.kernel.org, quic_c_gdjako@quicinc.com,
	iommu@lists.linux-foundation.org, sonnyrao@chromium.org,
	saiprakash.ranjan@codeaurora.org, linux-mmc@vger.kernel.org,
	vbadigan@codeaurora.org, rajatja@google.com,
	saravanak@google.com, joel@joelfernandes.org,
	Douglas Anderson <dianders@chromium.org>,
	Andy Gross <agross@kernel.org>,
	Bartosz Golaszewski <bgolaszewski@baylibre.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Heikki Krogerus <heikki.krogerus@linux.intel.com>,
	Randy Dunlap <rdunlap@infradead.org>,
	linux-kernel@vger.kernel.org
Subject: [PATCH 0/6] iommu: Enable devices to request non-strict DMA, starting with QCom SD/MMC
Date: Mon, 21 Jun 2021 16:52:42 -0700	[thread overview]
Message-ID: <20210621235248.2521620-1-dianders@chromium.org> (raw)

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