Re: [Qemu-devel] [RFC PATCH] memory: fix access_with_adjusted_size() on big-endian

[Paolo Bonzini <pbonzini@redhat.com>]

On 11/08/2017 16:06, Philippe Mathieu-Daudé wrote:
> remove unnecessary memory_region_big_endian()

Can you explain why it's unnecessary?...

Paolo

> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
> This is part of a branch with many cross-endianness tests for 2.11
> 
> Frederic does it helps your issues on armeb?
> 
>  memory.c | 28 ++++++++++------------------
>  1 file changed, 10 insertions(+), 18 deletions(-)
> 
> diff --git a/memory.c b/memory.c
> index c0adc35410..600f5d5b1a 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -338,15 +338,6 @@ static void flatview_simplify(FlatView *view)
>      }
>  }
>  
> -static bool memory_region_big_endian(MemoryRegion *mr)
> -{
> -#ifdef TARGET_WORDS_BIGENDIAN
> -    return mr->ops->endianness != DEVICE_LITTLE_ENDIAN;
> -#else
> -    return mr->ops->endianness == DEVICE_BIG_ENDIAN;
> -#endif
> -}
> -
>  static bool memory_region_wrong_endianness(MemoryRegion *mr)
>  {
>  #ifdef TARGET_WORDS_BIGENDIAN
> @@ -572,7 +563,8 @@ static MemTxResult access_with_adjusted_size(hwaddr addr,
>  {
>      uint64_t access_mask;
>      unsigned access_size;
> -    unsigned i;
> +    hwaddr access_addr;
> +    unsigned offset;
>      MemTxResult r = MEMTX_OK;
>  
>      if (!access_size_min) {
> @@ -585,17 +577,17 @@ static MemTxResult access_with_adjusted_size(hwaddr addr,
>      /* FIXME: support unaligned access? */
>      access_size = MAX(MIN(size, access_size_max), access_size_min);
>      access_mask = -1ULL >> (64 - access_size * 8);
> -    if (memory_region_big_endian(mr)) {
> -        for (i = 0; i < size; i += access_size) {
> -            r |= access(mr, addr + i, value, access_size,
> -                        (size - access_size - i) * 8, access_mask, attrs);
> +    access_addr = addr & ~(access_size - 1);
> +    if (access_size < size) {
> +        for (offset = 0; offset < size; offset += access_size) {
> +            r |= access(mr, access_addr + offset, value, access_size,
> +                        offset * 8, access_mask, attrs);
>          }
>      } else {
> -        for (i = 0; i < size; i += access_size) {
> -            r |= access(mr, addr + i, value, access_size, i * 8,
> -                        access_mask, attrs);
> -        }
> +        r = access(mr, access_addr, value, access_size,
> +                    0, access_mask, attrs);
>      }
> +
>      return r;
>  }
>  
>