Re: [PATCH 0/4] Generic IOMMU page table framework

[Laurent Pinchart <laurent.pinchart-ryLnwIuWjnjg/C1BVhZhaw@public.gmane.org>]

Hi Will,

Thank you for the patches.

On Thursday 27 November 2014 11:51:14 Will Deacon wrote:
> Hi all,
> 
> This series introduces a generic IOMMU page table allocation framework,
> implements support for ARM long-descriptors and then ports the arm-smmu
> driver over to the new code.
> 
> There are a few reasons for doing this:
> 
>   - Page table code is hard, and I don't enjoy shopping
> 
>   - A number of IOMMUs actually use the same table format, but currently
>     duplicate the code
> 
>   - It provides a CPU (and architecture) independent allocator, which
>     may be useful for some systems where the CPU is using a different
>     table format for its own mappings
> 
> As illustrated in the final patch, an IOMMU driver interacts with the
> allocator by passing in a configuration structure describing the
> input and output address ranges, the supported pages sizes and a set of
> ops for performing various TLB invalidation and PTE flushing routines.
> 
> The LPAE code implements support for 4k/2M/1G, 16k/32M and 64k/512M
> mappings, but I decided not to implement the contiguous bit in the
> interest of trying to keep the code semi-readable. This could always be
> added later, if needed.

Do you have any idea how much the contiguous bit can improve performances in 
real use cases ?

> I also included some self-tests for the LPAE implementation. Ideally
> we'd merge these, but I'm also happy to drop them if there are
> objections.
> 
> Tested with the self-tests, but also VFIO + MMU-500 at stage-1 and
> stage-2. Patches taken against my iommu/devel branch (queued by Joerg
> for 3.19).
> 
> All feedback welcome.
> 
> Will
> 
> --->8
> 
> Will Deacon (4):
>   iommu: introduce generic page table allocation framework
>   iommu: add ARM LPAE page table allocator
>   iommu: add self-consistency tests to ARM LPAE IO page table allocator
>   iommu/arm-smmu: make use of generic LPAE allocator
> 
>  MAINTAINERS                    |   1 +
>  arch/arm64/Kconfig             |   1 -
>  drivers/iommu/Kconfig          |  32 +-
>  drivers/iommu/Makefile         |   2 +
>  drivers/iommu/arm-smmu.c       | 872 +++++++++++---------------------------
>  drivers/iommu/io-pgtable-arm.c | 925 ++++++++++++++++++++++++++++++++++++++
>  drivers/iommu/io-pgtable.c     |  78 ++++
>  drivers/iommu/io-pgtable.h     |  77 ++++
>  8 files changed, 1361 insertions(+), 627 deletions(-)
>  create mode 100644 drivers/iommu/io-pgtable-arm.c
>  create mode 100644 drivers/iommu/io-pgtable.c
>  create mode 100644 drivers/iommu/io-pgtable.h

-- 
Regards,

Laurent Pinchart