Re: [PATCH v6 00/14] riscv: support for Svpbmt and D1 memory types

[Atish Patra]

On Wed, Feb 9, 2022 at 4:38 AM Heiko Stuebner <heiko@xxxxxxxxx> wrote:
>
> Svpbmt is an extension defining "Supervisor-mode: page-based memory types"
> for things like non-cacheable pages or I/O memory pages.
>
>
> So this is my 2nd try at implementing Svpbmt (and the diverging D1 memory
> types) using the alternatives framework.
>
> This includes a number of changes to the alternatives mechanism itself.
> The biggest one being the move to a more central location, as I expect
> in the future, nearly every chip needing some sort of patching, be it
> either for erratas or for optional features (svpbmt or others).
>
> The dt-binding for svpbmt itself is of course not finished and is still
> using the binding introduced in previous versions, as where to put
> a svpbmt-property in the devicetree is still under dicussion.
> Atish seems to be working on a framework for extensions [0],
>

Here is the patch series
https://lore.kernel.org/lkml/20220210214018.55739-1-atishp@xxxxxxxxxxxx/

I think we can simplify the cpu feature probing in PATCH 10 with the
above series
which simply relies on the existing riscv_isa bitmap.

We also don't need the separate svpbmt property in DT mmu node.
Let me know what you think.

> The series also introduces support for the memory types of the D1
> which are implemented differently to svpbmt. But when patching anyway
> it's pretty clean to add the D1 variant via ALTERNATIVE_2 to the same
> location.
>
> The only slightly bigger difference is that the "normal" type is not 0
> as with svpbmt, so kernel patches for this PMA type need to be applied
> even before the MMU is brought up, so the series introduces a separate
> stage for that.
>
>
> In theory this series is 3 parts:
> - sbi cache-flush / null-ptr
> - alternatives improvements
> - svpbmt+d1
>
> So expecially patches from the first 2 areas could be applied when
> deemed ready, I just thought to keep it together to show-case where
> the end-goal is and not requiring jumping between different series.
>
>
> The sbi cache-flush patch is based on Atish's sparse-hartid patch [1],
> as it touches a similar area in mm/cacheflush.c
>
>
> I picked the recipient list from the previous version, hopefully
> I didn't forget anybody.
>
> changes in v6:
> - rebase onto 5.17-rc1
> - handle sbi null-ptr differently
> - improve commit messages
> - use riscv,mmu as property name
>
> changes in v5:
> - move to use alternatives for runtime-patching
> - add D1 variant
>
>
> [0] https://lore.kernel.org/r/20211224211632.1698523-1-atishp@xxxxxxxxxxxx
> [1] https://lore.kernel.org/r/20220120090918.2646626-1-atishp@xxxxxxxxxxxx
>
>
> Heiko Stuebner (12):
>   riscv: prevent null-pointer dereference with sbi_remote_fence_i
>   riscv: integrate alternatives better into the main architecture
>   riscv: allow different stages with alternatives
>   riscv: implement module alternatives
>   riscv: implement ALTERNATIVE_2 macro
>   riscv: extend concatenated alternatives-lines to the same length
>   riscv: prevent compressed instructions in alternatives
>   riscv: move boot alternatives to a slightly earlier position
>   riscv: Fix accessing pfn bits in PTEs for non-32bit variants
>   riscv: add cpufeature handling via alternatives
>   riscv: remove FIXMAP_PAGE_IO and fall back to its default value
>   riscv: add memory-type errata for T-Head
>
> Wei Fu (2):
>   dt-bindings: riscv: add MMU Standard Extensions support for Svpbmt
>   riscv: add RISC-V Svpbmt extension support
>
>  .../devicetree/bindings/riscv/cpus.yaml       |  10 ++
>  arch/riscv/Kconfig.erratas                    |  29 ++--
>  arch/riscv/Kconfig.socs                       |   1 -
>  arch/riscv/Makefile                           |   2 +-
>  arch/riscv/errata/Makefile                    |   2 +-
>  arch/riscv/errata/sifive/errata.c             |  10 +-
>  arch/riscv/errata/thead/Makefile              |   1 +
>  arch/riscv/errata/thead/errata.c              |  85 +++++++++++
>  arch/riscv/include/asm/alternative-macros.h   | 114 ++++++++-------
>  arch/riscv/include/asm/alternative.h          |  16 ++-
>  arch/riscv/include/asm/errata_list.h          |  52 +++++++
>  arch/riscv/include/asm/fixmap.h               |   2 -
>  arch/riscv/include/asm/pgtable-32.h           |  17 +++
>  arch/riscv/include/asm/pgtable-64.h           |  79 +++++++++-
>  arch/riscv/include/asm/pgtable-bits.h         |  10 --
>  arch/riscv/include/asm/pgtable.h              |  53 +++++--
>  arch/riscv/include/asm/vendorid_list.h        |   1 +
>  arch/riscv/kernel/Makefile                    |   1 +
>  arch/riscv/{errata => kernel}/alternative.c   |  48 ++++++-
>  arch/riscv/kernel/cpufeature.c                | 136 +++++++++++++++++-
>  arch/riscv/kernel/head.S                      |   2 +
>  arch/riscv/kernel/module.c                    |  29 ++++
>  arch/riscv/kernel/sbi.c                       |  10 +-
>  arch/riscv/kernel/smpboot.c                   |   4 -
>  arch/riscv/kernel/traps.c                     |   2 +-
>  arch/riscv/mm/init.c                          |   1 +
>  26 files changed, 606 insertions(+), 111 deletions(-)
>  create mode 100644 arch/riscv/errata/thead/Makefile
>  create mode 100644 arch/riscv/errata/thead/errata.c
>  rename arch/riscv/{errata => kernel}/alternative.c (59%)
>
> --
> 2.30.2
>
>
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-- 
Regards,
Atish