Re: [PATCH v3 2/2] target/m68k: consolidate physical translation offset into get_physical_address()

[Laurent Vivier]

Le 30/06/2020 à 13:27, Mark Cave-Ayland a écrit :
> Since all callers to get_physical_address() now apply the same page offset to
> the translation result, move the logic into get_physical_address() itself to
> avoid duplication.
> 
> Suggested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> ---
>  target/m68k/helper.c | 18 +++++++-----------
>  1 file changed, 7 insertions(+), 11 deletions(-)
> 
> diff --git a/target/m68k/helper.c b/target/m68k/helper.c
> index 631eab7774..71c2376910 100644
> --- a/target/m68k/helper.c
> +++ b/target/m68k/helper.c
> @@ -643,7 +643,7 @@ static int get_physical_address(CPUM68KState *env, hwaddr 
> *physical,
>                  /* Transparent Translation Register bit */
>                  env->mmu.mmusr = M68K_MMU_T_040 | M68K_MMU_R_040;
>              }
> -            *physical = address & TARGET_PAGE_MASK;
> +            *physical = address;
>              *page_size = TARGET_PAGE_SIZE;
>              return 0;
>          }
> @@ -771,7 +771,8 @@ static int get_physical_address(CPUM68KState *env, hwaddr 
> *physical,
>      }
>      *page_size = 1 << page_bits;
>      page_mask = ~(*page_size - 1);
> -    *physical = next & page_mask;
> +    address &= TARGET_PAGE_MASK;

I don't think you need TARGET_PAGE_MASK here:
- TARGET_PAGE_MASK is 4096
- page_mask is either 4096 or 8192

> +    *physical = (next & page_mask) + (address & (*page_size - 1));
>  
>      if (access_type & ACCESS_PTEST) {
>          env->mmu.mmusr |= next & M68K_MMU_SR_MASK_040;
> @@ -826,8 +827,6 @@ hwaddr m68k_cpu_get_phys_page_debug(CPUState *cs, vaddr 
> addr)
>          return -1;
>      }
>  
> -    addr &= TARGET_PAGE_MASK;
> -    phys_addr += addr & (page_size - 1);
>      return phys_addr;
>  }
>  
> @@ -891,10 +890,8 @@ bool m68k_cpu_tlb_fill(CPUState *cs, vaddr address, int 
> size,
>      ret = get_physical_address(&cpu->env, &physical, &prot,
>                                 address, access_type, &page_size);
>      if (likely(ret == 0)) {
> -        address &= TARGET_PAGE_MASK;
> -        physical += address & (page_size - 1);
> -        tlb_set_page(cs, address, physical,
> -                     prot, mmu_idx, TARGET_PAGE_SIZE);
> +        tlb_set_page(cs, address & TARGET_PAGE_MASK,
> +                     physical & TARGET_PAGE_MASK, prot, mmu_idx, page_size);

I had a look to tl_set_page() to see how it manages the entry when the
addresses are not aligned to page_size, and it calls
tlb_set_page_with_attrs() where we have a comment:

/* Add a new TLB entry. At most one entry for a given virtual address
 * is permitted. Only a single TARGET_PAGE_SIZE region is mapped, the
 * supplied size is only used by tlb_flush_page.
...

So I think it's correct to use TARGET_PAGE_MASK and page_size.

Thanks,
Laurent