Re: [RFC PATCH 29/34] accel/tcg: Make tb-maint.c target indpendent

[Richard Henderson]

On 1/20/24 00:40, Anton Johansson wrote:
> Uses target_has_precise_smc() and target_phys_addr_space_bits() to turn
> ifdefs into runtime branches.
>
> Signed-off-by: Anton Johansson <anjo@rev.ng>
> ---
>   accel/tcg/tb-maint.c | 47 +++++++++++++++++++++++---------------------
>   1 file changed, 25 insertions(+), 22 deletions(-)
>
> diff --git a/accel/tcg/tb-maint.c b/accel/tcg/tb-maint.c
> index b194f8f065..fdc3a30d0d 100644
> --- a/accel/tcg/tb-maint.c
> +++ b/accel/tcg/tb-maint.c
> @@ -148,14 +148,6 @@ static PageForEachNext foreach_tb_next(PageForEachNext tb,
>   }
>   
>   #else
> -/*
> - * In system mode we want L1_MAP to be based on ram offsets.
> - */
> -#if HOST_LONG_BITS < TARGET_PHYS_ADDR_SPACE_BITS
> -# define L1_MAP_ADDR_SPACE_BITS  HOST_LONG_BITS
> -#else
> -# define L1_MAP_ADDR_SPACE_BITS  TARGET_PHYS_ADDR_SPACE_BITS
> -#endif

I'm not keen on this.  We can make this target independent in several ways:

(1) Use fixed constants that cover all 64 phys addr bits,
(2) Use a different data structure entirely (e.g. IntervalTree).

Preserving the existing data structure, using variables, seems like a poor 
choice.

> @@ -1045,14 +1048,15 @@ bool tb_invalidate_phys_page_unwind(tb_page_addr_t 
> addr, uintptr_t pc)
>       TranslationBlock *tb;
>       PageForEachNext n;
>       tb_page_addr_t last;
> +    const bool has_precise_smc = target_has_precise_smc();
>   
>       /*
>        * Without precise smc semantics, or when outside of a TB,
>        * we can skip to invalidate.
>        */
> -#ifndef TARGET_HAS_PRECISE_SMC
> -    pc = 0;
> -#endif
> +    if (!has_precise_smc) {
> +        pc = 0;
> +    }

Ok to this part.  Split it out.


r~