Re: [PATCH v6 00/25] iommu: Shared Virtual Addressing for SMMUv3

Jacob Pan
2020-04-30T21:13:59Z

On Thu, 30 Apr 2020 16:33:59 +0200
Jean-Philippe Brucker <jean-philippe@linaro.org> wrote:

> Shared Virtual Addressing (SVA) allows to share process page tables
> with devices using the IOMMU, PASIDs and I/O page faults. Add SVA
> support to the Arm SMMUv3 driver.
>
> Since v5 [1]:
>
> * Added patches 1-3. Patch 1 adds a PASID field to mm_struct as
> discussed in [1] and [2]. This is also needed for Intel ENQCMD.
> Patch 2 adds refcounts to IOASID and patch 3 adds a couple of helpers
> to allocate the PASID.
>
> * Dropped most of iommu-sva.c. After getting rid of io_mm following
> review of v5, there wasn't enough generic code left to justify the
> indirect branch overhead of io_mm_ops in the MMU notifiers. I ended
> up with more glue than useful code, and couldn't find an easy way to
> deal with domains in the SMMU driver (we keep PASID tables per domain,
> while x86 keeps them per device). The direct approach in patch 17 is
> nicer and a little easier to read. The SMMU driver only gained 160
> lines, while iommu-sva lost 470 lines.
>
> As a result I dropped the MMU notifier patch.
>
> Jacob, one upside of this rework is that we now free ioasids in
> blocking context, which might help with your addition of notifiers
> to ioasid.c
>
Thanks for the note. It does make notifier much easier, plus the
refcount can alleviate the constraint on ordering.

I guess we don't share mmu notifier code for now :)

> * Simplified io-pgfault a bit, since flush() isn't called from mm exit
> path anymore.
>
> * Fixed a bug in patch 17 (don't clear the stall bit when stall is
> forced).
>
> You can find the latest version on https://jpbrucker.net/git/linux
> branch sva/current, and sva/zip-devel for the Hisilicon zip
> accelerator.
>
> [1]
> https://lore.kernel.org/linux-iommu/20200414170252.714402-1-jean-philippe@linaro.org/
> [2]
> https://lore.kernel.org/linux-iommu/1585596788-193989-6-git-send-email-fenghua.yu@intel.com/
>
> Jean-Philippe Brucker (25):
> mm: Add a PASID field to mm_struct
> iommu/ioasid: Add ioasid references
> iommu/sva: Add PASID helpers
> iommu: Add a page fault handler
> iommu/iopf: Handle mm faults
> arm64: mm: Add asid_gen_match() helper
> arm64: mm: Pin down ASIDs for sharing mm with devices
> iommu/io-pgtable-arm: Move some definitions to a header
> iommu/arm-smmu-v3: Manage ASIDs with xarray
> arm64: cpufeature: Export symbol read_sanitised_ftr_reg()
> iommu/arm-smmu-v3: Share process page tables
> iommu/arm-smmu-v3: Seize private ASID
> iommu/arm-smmu-v3: Add support for VHE
> iommu/arm-smmu-v3: Enable broadcast TLB maintenance
> iommu/arm-smmu-v3: Add SVA feature checking
> iommu/arm-smmu-v3: Add SVA device feature
> iommu/arm-smmu-v3: Implement iommu_sva_bind/unbind()
> iommu/arm-smmu-v3: Hook up ATC invalidation to mm ops
> iommu/arm-smmu-v3: Add support for Hardware Translation Table Update
> iommu/arm-smmu-v3: Maintain a SID->device structure
> dt-bindings: document stall property for IOMMU masters
> iommu/arm-smmu-v3: Add stall support for platform devices
> PCI/ATS: Add PRI stubs
> PCI/ATS: Export PRI functions
> iommu/arm-smmu-v3: Add support for PRI
>
> drivers/iommu/Kconfig | 11 +
> drivers/iommu/Makefile | 2 +
> .../devicetree/bindings/iommu/iommu.txt | 18 +
> arch/arm64/include/asm/mmu.h | 1 +
> arch/arm64/include/asm/mmu_context.h | 11 +-
> drivers/iommu/io-pgtable-arm.h | 30 +
> drivers/iommu/iommu-sva.h | 15 +
> include/linux/ioasid.h | 10 +-
> include/linux/iommu.h | 53 +
> include/linux/mm_types.h | 4 +
> include/linux/pci-ats.h | 8 +
> arch/arm64/kernel/cpufeature.c | 1 +
> arch/arm64/mm/context.c | 103 +-
> drivers/iommu/arm-smmu-v3.c | 1554
> +++++++++++++++-- drivers/iommu/io-pgfault.c |
> 458 +++++ drivers/iommu/io-pgtable-arm.c | 27 +-
> drivers/iommu/ioasid.c | 30 +-
> drivers/iommu/iommu-sva.c | 85 +
> drivers/iommu/of_iommu.c | 5 +-
> drivers/pci/ats.c | 4 +
> MAINTAINERS | 3 +-
> 21 files changed, 2275 insertions(+), 158 deletions(-)
> create mode 100644 drivers/iommu/io-pgtable-arm.h
> create mode 100644 drivers/iommu/iommu-sva.h
> create mode 100644 drivers/iommu/io-pgfault.c
> create mode 100644 drivers/iommu/iommu-sva.c
>

[Jacob Pan]