Re: [Qemu-devel] [RFC PATCH v2 3/6] memory: add memory_region_to_address()

[Peter Maydell]

On 16 April 2013 00:19, Scott Wood <address@hidden> wrote:
> This is useful for when a user of the memory region API needs to
> communicate the absolute bus address to something outside QEMU
> (in particular, KVM).
>
> Signed-off-by: Scott Wood <address@hidden>
> ---
> TODO: Use add/del memory listeners later in the patchset, which would
> eliminate the need for this patch.

Yes, please do.

> +/* memory_region_to_address: Find the full address of the start of the
> + *      given #MemoryRegion, ignoring aliases.  There is no guarantee
> + *      that the #MemoryRegion is actually visible at this address, if
> + *      there are overlapping regions.
> + *
> + * @mr: #MemoryRegion being queried
> + * @asp: if non-NULL, returns the #AddressSpace @mr is mapped in, if any
> + */
> +hwaddr memory_region_to_address(MemoryRegion *mr, AddressSpace **asp);

A MemoryRegion can appear in more than one AddressSpace (or none at all),
so I don't think this is a very clearly defined API to put in the
memory API itself. (It's ok to make that kind of assumption as a user
of the memory APIs for particular cases, eg in how a memory listener
callback function behaves. But we shouldn't be baking those assumptions
into new API functions.)

thanks
-- PMM