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

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Philippe Mathieu-Daudé (philmd@redhat.com) wrote:
> On 8/14/19 7:25 PM, Dr. David Alan Gilbert wrote:
> > * Philippe Mathieu-Daudé (philmd@redhat.com) wrote:
> >> Hi David,
> >>
> >> On 8/13/19 12:29 PM, Dr. David Alan Gilbert (git) wrote:
> >>> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> >>>
> >>> 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"
> > 
> > Oops thanks.
> > 
> >> 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.
> > 
> > OK, what I'll do is I'll split this one into two ; I feel better
> > having the extra function here separate from the next commit.
> 
> Thanks, feel free to add to both:
> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Thanks!

> >> Doesn't Clang warn about unused 'static inline' btw?
> > 
> > I was using gcc; but we seem to have loads of static inline's - what
> > would make this one different?
> 
> I guess I was confused with 'static (no-inline)' :)
> 
> >>>
> >>> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> >>> ---
> >>>  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
> >>>   *
> >>>
> > --
> > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
> > 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK