Re: [Qemu-devel] [RFC] Memory API

[Gleb Natapov]

On Sun, May 22, 2011 at 02:29:27PM +0300, Avi Kivity wrote:
> On 05/22/2011 01:53 PM, Jan Kiszka wrote:
> >On 2011-05-22 10:41, Gleb Natapov wrote:
> >>>  The chipset knows about the priorities.  How to communicate them to
> >>>  the core?
> >>>
> >>>  - at runtime, with hierarchical dispatch of ->read() and ->write():
> >>>  slow, and doesn't work at all for RAM.
> >>>  - using registration order: fragile
> >>>  - using priorities
> >>>
> >>  - by resolving overlapping and registering flattened list with the core.
> >>    (See example above).
> >
> >[Registration would happens with the help of the core against the next
> >higher layer.]
> >
> >To do this, you need to
> >  - open-code the resolution logic at every level (very bad idea)
> >  - provide library services to obtain a flattened representation
> >
> >Please try to specify such an API without any parameters that are
> >priority-like.
> 
> Another way of saying the same thing:  having the chipset code
> resolve conflicts, and having the chipset code assign priorities,
> are equivalent.  But having priorities allows flattening to take
> place without further involvement of the chipset code.
> 
Yes, that's basically sums it up. My main concern with API was that it
was not clear how two independent pieces of code would know how to
assign priorities. But if all registrations happen hierarchically there
will be no such "independent pieces of code".


--
                        Gleb.