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:
> 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.

> 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?

Dave

> > 
> > 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