Re: [PATCH v2 6/6] RISC-V: hwprobe: Document unaligned vector perf key

[Evan Green]

On Thu, Jun 13, 2024 at 12:18 PM Jesse Taube <jesse@xxxxxxxxxxxx> wrote:
>
> Document key for reporting the speed of unaligned vector accesses.
> The descriptions are the same as the scalar equivalent values.
>
> Signed-off-by: Jesse Taube <jesse@xxxxxxxxxxxx>
> ---
> V1 -> V2:
>   - New patch
> ---
>  Documentation/arch/riscv/hwprobe.rst | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/Documentation/arch/riscv/hwprobe.rst b/Documentation/arch/riscv/hwprobe.rst
> index 7085a694b801..344bea1e21bd 100644
> --- a/Documentation/arch/riscv/hwprobe.rst
> +++ b/Documentation/arch/riscv/hwprobe.rst
> @@ -236,3 +236,19 @@ The following keys are defined:
>
>  * :c:macro:`RISCV_HWPROBE_KEY_ZICBOZ_BLOCK_SIZE`: An unsigned int which
>    represents the size of the Zicboz block in bytes.
> +
> +* :c:macro:`RISCV_HWPROBE_KEY_VEC_MISALIGNED_PERF`: An enum value describing the
> +  performance of misaligned vector accesses on the selected set of processors.
> +
> +  * :c:macro:`RISCV_HWPROBE_VEC_MISALIGNED_UNKNOWN`: The performance of misaligned
> +    accesses is unknown.
> +
> +  * :c:macro:`RISCV_HWPROBE_VEC_MISALIGNED_SLOW`: Misaligned accesses are slower

Should we specify what size of vector access we're comparing against?
In other words, crispen up what "misaligned access" exactly means. I
realize you copied this from my text. I really should have said
"misaligned native word size accesses".

> +    than equivalent byte accesses.  Misaligned accesses may be supported
> +    directly in hardware, or trapped and emulated by software.
> +
> +  * :c:macro:`RISCV_HWPROBE_VEC_MISALIGNED_FAST`: Misaligned accesses are faster
> +    than equivalent byte accesses.
> +
> +  * :c:macro:`RISCV_HWPROBE_VEC_MISALIGNED_UNSUPPORTED`: Misaligned accesses are
> +    not supported at all and will generate a misaligned address fault.
> --
> 2.43.0
>