Re: [Qemu-devel] [PATCH 1/2] memory: Align and add helper for comparing MemoryRegionSections

[Philippe Mathieu-Daudé]

Hi David,

On 8/13/19 12:29 PM, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <address@hidden>
> 
> MemoryRegionSection includes an Int128 'size' field;
> on some platforms the compiler causes an alignment of this to
> a 128bit boundary, leaving 8 bytes of dead space.
> This deadspace can be filled with junk.
> 
> Move the size field to the top avoiding unnecsssary alignment

"unnecessary"

This is enough change to be in its own commit.

---

> and provide an 'eq' routine to safely compare MRS's.

This is another change, and should be squashed in the next patch IMO.
Doesn't Clang warn about unused 'static inline' btw?

> 
> Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> ---
>  include/exec/memory.h | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index 606250172a..ce62e847bd 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -487,15 +487,27 @@ static inline FlatView 
> *address_space_to_flatview(AddressSpace *as)
>   * @nonvolatile: this section is non-volatile
>   */
>  struct MemoryRegionSection {
> +    Int128 size;
>      MemoryRegion *mr;
>      FlatView *fv;
>      hwaddr offset_within_region;
> -    Int128 size;
>      hwaddr offset_within_address_space;
>      bool readonly;
>      bool nonvolatile;
>  };
>  
> +static inline bool MemoryRegionSection_eq(MemoryRegionSection *a,
> +                                          MemoryRegionSection *b)
> +{
> +    return a->mr == b->mr &&
> +           a->fv == b->fv &&
> +           a->offset_within_region == b->offset_within_region &&
> +           a->offset_within_address_space == b->offset_within_address_space 
> &&
> +           int128_eq(a->size, b->size) &&
> +           a->readonly == b->readonly &&
> +           a->nonvolatile == b->nonvolatile;
> +}
> +
>  /**
>   * memory_region_init: Initialize a memory region
>   *
>