linux-kernel - Re: [PATCH v5 0/4] Add support for SBI v0.2

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Date:   Wed, 04 Dec 2019 10:56:28 -0800 (PST)
From:   Palmer Dabbelt <palmerdabbelt@...gle.com>
To:     Atish Patra <Atish.Patra@....com>
CC:     linux-kernel@...r.kernel.org, Atish Patra <Atish.Patra@....com>,
        aou@...s.berkeley.edu, alexios.zavras@...el.com,
        anup@...infault.org, linux-riscv@...ts.infradead.org,
        han_mao@...ky.com, rppt@...ux.ibm.com,
        Paul Walmsley <paul.walmsley@...ive.com>, tglx@...utronix.de
Subject:     Re: [PATCH v5 0/4] Add support for SBI v0.2 

On Tue, 26 Nov 2019 11:04:59 PST (-0800), Atish Patra wrote:
> The Supervisor Binary Interface(SBI) specification[1] now defines a
> base extension that provides extendability to add future extensions
> while maintaining backward compatibility with previous versions.
> The new version is defined as 0.2 and older version is marked as 0.1.
>
> This series adds support v0.2 and a unified calling convention
> implementation between 0.1 and 0.2. It also add other SBI v0.2
> functionality defined in [2]. The base support for SBI v0.2 is already
> available in OpenSBI v0.5. This series needs additional patches[3] in
> OpenSBI.
>
> Tested on both BBL, OpenSBI with/without the above patch series.
>
> [1] https://github.com/riscv/riscv-sbi-doc/blob/master/riscv-sbi.adoc
> [2] https://github.com/riscv/riscv-sbi-doc/pull/27
> [3] http://lists.infradead.org/pipermail/opensbi/2019-November/000738.html
>
> Changes from v4->v5
> 1. Fixed few minor comments related to static & inline.
> 2. Make sure that every patch is boot tested individually.
>
> Changes from v3->v4.
> 1. Rebased on top of for-next.
> 2. Fixed issuses with checkpatch --strict.
> 3. Unfied all IPI/fence related functions.
> 4. Added Hfence related SBI calls.
> 5. Moved to function pointer based boot time switch between v01 and v02 calls.
> Changes from v2->v3.
> 1. Moved v0.1 extensions to a new config.
> 2. Added support for relacement extensions of v0.1 extensions.
>
> Changes from v1->v2
> 1. Removed the legacy calling convention.
> 2. Moved all SBI related calls to sbi.c.
> 3. Moved all SBI related macros to uapi.
>
> Atish Patra (4):
> RISC-V: Mark existing SBI as 0.1 SBI.
> RISC-V: Add basic support for SBI v0.2
> RISC-V: Introduce a new config for SBI v0.1
> RISC-V: Implement new SBI v0.2 extensions
>
> arch/riscv/Kconfig           |   6 +
> arch/riscv/include/asm/sbi.h | 177 +++++++-----
> arch/riscv/kernel/Makefile   |   1 +
> arch/riscv/kernel/sbi.c      | 547 ++++++++++++++++++++++++++++++++++-
> arch/riscv/kernel/setup.c    |   2 +
> 5 files changed, 660 insertions(+), 73 deletions(-)

There's a few issues with the implementation, but I think the bigger question
is what do to with the spec.  The SBI stuff sort of snuck in to Linux without
actually having a proper spec written down, so I'm happy to just say "let's
take the 0.2 stuff as soon as it's frozen" as we're at least in a better spot
than with the legacy stuff.  Nominally we'd need to wait for a ratified
specification here, which probably means a 1.0 specification, but that's a way
off and I don't want to just sit around on the legacy stuff.