Re: [Qemu-devel] [PATCH 2/2] trace: show MemoryRegion name, not address

[Hollis Blanchard]

On 11/13/2015 02:23 AM, Stefan Hajnoczi wrote:
> On Wed, Nov 11, 2015 at 05:09:58PM -0800, Hollis Blanchard wrote:
> > Recording the MemoryRegion pointers isn't helpful, especially since no trace
> > data allows us to correlate those pointers to devices. Instead, record the
> > MemoryRegion name.
> >
> > Signed-off-by: Hollis Blanchard <address@hidden>
> > ---
> >   memory.c     | 12 ++++++------
> >   trace-events |  4 ++--
> >   2 files changed, 8 insertions(+), 8 deletions(-)
> >
> > diff --git a/memory.c b/memory.c
> > index c435c88..9bd4c31 100644
> > --- a/memory.c
> > +++ b/memory.c
> > @@ -381,7 +381,7 @@ static MemTxResult 
> > memory_region_oldmmio_read_accessor(MemoryRegion *mr,
> >       uint64_t tmp;
> >   
> >       tmp = mr->ops->old_mmio.read[ctz32(size)](mr->opaque, addr);
> > -    trace_memory_region_ops_read(mr, addr, tmp, size);
> > +    trace_memory_region_ops_read(mr->name, addr, tmp, size);
> mr->name may be NULL.  There is a memory_region_name() function that
> always produces a real string.  Perhaps it's best to use it.

Using memory_region_name() yields this:
** ERROR **: file qom/object.c: line 1427 
(object_get_canonical_path_component): assertion failed: (obj->parent != 
NULL)
aborting...

The offending MemoryRegion seems to be a subpage one, which has no name. 
I can tell because ops contains links to subpage_read() and subpage_write().

"info mtree" uses memory_region_name() and works fine, but perhaps 
that's because it only goes 2 levels deep?

Hollis Blanchard
Mentor Graphics Emulation Division