[RFC,v3,1/2] memory: allow MemoryRegion's priority field to accept negative values

Priority is used to make visible some subregions by obscuring
the parent MemoryRegion addresses overlapping with the subregion.

By allowing the priority to be negative the opposite can be done:
Allow a subregion to be visible on all the addresses not covered
by the parent MemoryRegion or other subregions.

Signed-off-by: Marcel Apfelbaum <marcel.a@redhat.com>
---
 include/exec/memory.h | 6 +++---
 memory.c              | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

On Mon, Sep 09, 2013 at 02:21:35PM +0300, Marcel Apfelbaum wrote:
> Priority is used to make visible some subregions by obscuring
> the parent MemoryRegion addresses overlapping with the subregion.
> 
> By allowing the priority to be negative the opposite can be done:
> Allow a subregion to be visible on all the addresses not covered
> by the parent MemoryRegion or other subregions.
> 
> Signed-off-by: Marcel Apfelbaum <marcel.a@redhat.com>

Seems harmless enough.

Reviewed-by: Michael S. Tsirkin <mst@redhat.com>


> ---
>  include/exec/memory.h | 6 +++---
>  memory.c              | 2 +-
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index ebe0d24..6995087 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -153,7 +153,7 @@ struct MemoryRegion {
>      bool flush_coalesced_mmio;
>      MemoryRegion *alias;
>      hwaddr alias_offset;
> -    unsigned priority;
> +    int priority;
>      bool may_overlap;
>      QTAILQ_HEAD(subregions, MemoryRegion) subregions;
>      QTAILQ_ENTRY(MemoryRegion) subregions_link;
> @@ -193,7 +193,7 @@ struct MemoryListener {
>      void (*coalesced_mmio_del)(MemoryListener *listener, MemoryRegionSection *section,
>                                 hwaddr addr, hwaddr len);
>      /* Lower = earlier (during add), later (during del) */
> -    unsigned priority;
> +    int priority;
>      AddressSpace *address_space_filter;
>      QTAILQ_ENTRY(MemoryListener) link;
>  };
> @@ -779,7 +779,7 @@ void memory_region_add_subregion(MemoryRegion *mr,
>  void memory_region_add_subregion_overlap(MemoryRegion *mr,
>                                           hwaddr offset,
>                                           MemoryRegion *subregion,
> -                                         unsigned priority);
> +                                         int priority);
>  
>  /**
>   * memory_region_get_ram_addr: Get the ram address associated with a memory
> diff --git a/memory.c b/memory.c
> index 5a10fd0..984a3dc 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -1473,7 +1473,7 @@ void memory_region_add_subregion(MemoryRegion *mr,
>  void memory_region_add_subregion_overlap(MemoryRegion *mr,
>                                           hwaddr offset,
>                                           MemoryRegion *subregion,
> -                                         unsigned priority)
> +                                         int priority)
>  {
>      subregion->may_overlap = true;
>      subregion->priority = priority;
> -- 
> 1.8.3.1

On 9 September 2013 12:41, Michael S. Tsirkin <mst@redhat.com> wrote:
> On Mon, Sep 09, 2013 at 02:21:35PM +0300, Marcel Apfelbaum wrote:
>> Priority is used to make visible some subregions by obscuring
>> the parent MemoryRegion addresses overlapping with the subregion.
>>
>> By allowing the priority to be negative the opposite can be done:
>> Allow a subregion to be visible on all the addresses not covered
>> by the parent MemoryRegion or other subregions.
>>
>> Signed-off-by: Marcel Apfelbaum <marcel.a@redhat.com>
>
> Seems harmless enough.
>
> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

No, the idea is good but this version is just broken.
See the comments I made on the previous version which
Marcel ignored :-(

-- PMM

On Mon, Sep 09, 2013 at 12:45:12PM +0100, Peter Maydell wrote:
> On 9 September 2013 12:41, Michael S. Tsirkin <mst@redhat.com> wrote:
> > On Mon, Sep 09, 2013 at 02:21:35PM +0300, Marcel Apfelbaum wrote:
> >> Priority is used to make visible some subregions by obscuring
> >> the parent MemoryRegion addresses overlapping with the subregion.
> >>
> >> By allowing the priority to be negative the opposite can be done:
> >> Allow a subregion to be visible on all the addresses not covered
> >> by the parent MemoryRegion or other subregions.
> >>
> >> Signed-off-by: Marcel Apfelbaum <marcel.a@redhat.com>
> >
> > Seems harmless enough.
> >
> > Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> 
> No, the idea is good but this version is just broken.
> See the comments I made on the previous version which
> Marcel ignored :-(
> 
> -- PMM

You are right, I missed the bugs.
Good catch, thanks.

On Mon, Sep 09, 2013 at 02:48:55PM +0300, Michael S. Tsirkin wrote:
> On Mon, Sep 09, 2013 at 12:45:12PM +0100, Peter Maydell wrote:
> > On 9 September 2013 12:41, Michael S. Tsirkin <mst@redhat.com> wrote:
> > > On Mon, Sep 09, 2013 at 02:21:35PM +0300, Marcel Apfelbaum wrote:
> > >> Priority is used to make visible some subregions by obscuring
> > >> the parent MemoryRegion addresses overlapping with the subregion.
> > >>
> > >> By allowing the priority to be negative the opposite can be done:
> > >> Allow a subregion to be visible on all the addresses not covered
> > >> by the parent MemoryRegion or other subregions.
> > >>
> > >> Signed-off-by: Marcel Apfelbaum <marcel.a@redhat.com>
> > >
> > > Seems harmless enough.
> > >
> > > Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> > 
> > No, the idea is good but this version is just broken.
> > See the comments I made on the previous version which
> > Marcel ignored :-(
> > 
> > -- PMM
> 
> You are right, I missed the bugs.
> Good catch, thanks.
> 

So I guess it's only an Acked-by: Michael S. Tsirkin <mst@redhat.com>
at this point :)