[PATCH v2] Align SBI trap registers to a nice boundary for performance reasons.

[Anup Patel]

On Tue, Feb 11, 2025 at 4:41 AM Raj Vishwanathan
<raj.vishwanathan at gmail.com> wrote:
>
> Align SBI_TRAP_CONTEXT_SIZE to a multiple of 16 bytes. If it is not
> aligned to 16 bytes for RV64, it can create performance problems.
> Aligning it correctly can fix the performance issues.
>
> Signed-off-by: Raj Vishwanathan <Raj.Vishwanathan at gmail.com>

Simplify the patch subject and use "include: sbi:" as subject prefix.

Regards,
Anup

> ---
> Test: Performance issues seen and fix Verified on FPGA.
> Other methods.
>     Run qemu with monitor to check the SP during cpu_in
>     and cpu_out.
>     Add sbi_printf to the function sbi_trap_handler to check
>     the alignment of sbi_trap_context
> ---
>  include/sbi/sbi_trap.h | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/include/sbi/sbi_trap.h b/include/sbi/sbi_trap.h
> index d5182bf..5eec4da 100644
> --- a/include/sbi/sbi_trap.h
> +++ b/include/sbi/sbi_trap.h
> @@ -112,10 +112,13 @@
>  /** Size (in bytes) of sbi_trap_info */
>  #define SBI_TRAP_INFO_SIZE SBI_TRAP_INFO_OFFSET(last)
>
> +#define STACK_BOUNDARY 16
> +#define ALIGN_TO_BOUNDARY(x, a) (((x) + (a) - 1) & ~((a) - 1))
> +
>  /** Size (in bytes) of sbi_trap_context */
> -#define SBI_TRAP_CONTEXT_SIZE (SBI_TRAP_REGS_SIZE + \
> +#define SBI_TRAP_CONTEXT_SIZE ALIGN_TO_BOUNDARY((SBI_TRAP_REGS_SIZE + \
>                                SBI_TRAP_INFO_SIZE + \
> -                              __SIZEOF_POINTER__)
> +                              __SIZEOF_POINTER__), STACK_BOUNDARY)
>
>  #ifndef __ASSEMBLER__
>
> --
> 2.43.0
>
>
> --
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