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

[Gleb Natapov]

On Thu, May 19, 2011 at 06:25:14PM +0200, Jan Kiszka wrote:
> On 2011-05-19 18:17, Gleb Natapov wrote:
> > On Thu, May 19, 2011 at 05:40:50PM +0300, Avi Kivity wrote:
> >> On 05/19/2011 05:37 PM, Anthony Liguori wrote:
> >>>
> >>> So....  do you do:
> >>>
> >>> isa_register_region(ISABus *bus, MemoryRegion *mr, int priority)
> >>> {
> >>>    chipset_register_region(bus->chipset, mr, priority + 1);
> >>> }
> >>>
> >>> I don't really understand how you can fold everything into one
> >>> table and not allow devices to override their parents using
> >>> priorities.
> >>
> >> Think of how a window manager folds windows with priorities onto a
> >> flat framebuffer.
> >>
> >> You do a depth-first walk of the tree.  For each child list, you
> >> iterate it from the lowest to highest priority, allowing later
> >> subregions override earlier subregions.
> >>
> > And how you set those priorities in a sensible way? Why two device on a
> > PCI bus will want to register their memory region with anything but
> > highest priority? And if you let PCI subsystem to assign priorities how
> > it will coordinate with ISA subsystem/memory controller what priorities
> > to assign to get meaningful system?
> 
> Priorities >default will only be used for explicit overlays, e.g. RAM
> over MMIO in PAM regions. Non-default priorities won't be assigned to
> normal PCI bars or any other device's region.
> 
That does not explain who and how assign those priorities in globally
meaningful way.

--
                        Gleb.