On 22/06/2021 00:52, Douglas Anderson wrote:
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. :(
JFYI, In case to missed it, and I know it's not the same thing as you want, above, but the following series will allow you to build the kernel to default to lazy mode:
https://lore.kernel.org/linux-iommu/1624016058-189713-1-git-send-email-john.garry@xxxxxxxxxx/T/#m21bc07b9353b3ba85f2a40557645c2bcc13cbb3e So iommu.strict=0 would be no longer always required for arm64. Thanks, John
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(-)
