Re: [Qemu-devel] [RFC v2 04/32] qemu_ram_block_host_offset

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

* Philippe Mathieu-Daudé (f4bug@amsat.org) wrote:
> Hi David,
> 
> On 08/24/2017 04:27 PM, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> > 
> > Utility to give the offset of a host pointer within a RAMBlock
> > (assuming we already know it's in that RAMBlock)
> > 
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > ---
> >   exec.c                    | 10 ++++++++++
> >   include/exec/cpu-common.h |  1 +
> >   2 files changed, 11 insertions(+)
> > 
> > diff --git a/exec.c b/exec.c
> > index 67df2909ce..35b4cea2ed 100644
> > --- a/exec.c
> > +++ b/exec.c
> > @@ -2231,6 +2231,16 @@ static void *qemu_ram_ptr_length(RAMBlock *ram_block, ram_addr_t addr,
> >       return ramblock_ptr(block, addr);
> >   }
> > +/* Return the offset of a hostpointer within a ramblock */
> > +ram_addr_t qemu_ram_block_host_offset(RAMBlock *rb, void *host)
> > +{
> > +    ram_addr_t res = (uint8_t *)host - (uint8_t *)rb->host;
> 
> What about using ptrdiff_t here,

We tend to use ram_addr_t for offsets in RAM, and so that's
the return type of the function, and we're also comparing this
value to rb->max_length below which is also a ram_addr_t.

> > +    assert((uint8_t *)host >= (uint8_t *)rb->host);
> 
> and uintptr_t here?

Done.

Thanks,

Dave

> > +    assert(res < rb->max_length);
> > +
> > +    return res;
> > +}
> > +
> >   /*
> >    * Translates a host ptr back to a RAMBlock, a ram_addr and an offset
> >    * in that RAMBlock.
> > diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
> > index 74341b19d2..0d861a6289 100644
> > --- a/include/exec/cpu-common.h
> > +++ b/include/exec/cpu-common.h
> > @@ -68,6 +68,7 @@ ram_addr_t qemu_ram_addr_from_host(void *ptr);
> >   RAMBlock *qemu_ram_block_by_name(const char *name);
> >   RAMBlock *qemu_ram_block_from_host(void *ptr, bool round_offset,
> >                                      ram_addr_t *offset);
> > +ram_addr_t qemu_ram_block_host_offset(RAMBlock *rb, void *host);
> >   void qemu_ram_set_idstr(RAMBlock *block, const char *name, DeviceState *dev);
> >   void qemu_ram_unset_idstr(RAMBlock *block);
> >   const char *qemu_ram_get_idstr(RAMBlock *rb);
> > 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK