Re: [RFC v2 01/20] Hierarchical memory region API

Avi Kivity
2011-06-28T11:53:29Z

On 06/28/2011 01:28 PM, Jan Kiszka wrote:
> On 2011-06-28 12:03, Michael S. Tsirkin wrote:
> >> +struct MemoryRegion {
> >> + /* All fields are private - violators will be prosecuted */
> >> + const MemoryRegionOps *ops;
> >> + MemoryRegion *parent;
> >> + uint64_t size;
> >> + target_phys_addr_t addr;
> >> + target_phys_addr_t offset;
> >> + ram_addr_t ram_addr;
> >> + bool has_ram_addr;
> >> + MemoryRegion *alias;
> >> + target_phys_addr_t alias_offset;
> >> + unsigned priority;
> >> + bool may_overlap;
> >> + QTAILQ_HEAD(subregions, MemoryRegion) subregions;
> >> + QTAILQ_ENTRY(MemoryRegion) subregions_link;
> >> + QTAILQ_HEAD(coalesced_ranges, CoalescedMemoryRange) coalesced;
> >> + const char *name;
> >
> > I'm never completely sure whether these should be target addresses
> > or bus addresses or just uint64_t.
> > With pci on a 32 bit system you can stick a 64 bit address
> > in a BAR and the result will be that it is never accessed
> > from the CPU.
> >
>
> Memory regions are not bound to any current or future PCI
> specifications. Any fixed bit width would be wrong here, ie. size should
> rather be target_phys_addr_t.

The point is that different buses have different widths.
target_phys_addr_t matches just one bus in the system. It needs to be
the maximum size of all buses present to be useful.

--
error compiling committee.c: too many arguments to function