On 05/22/2011 03:06 PM, Blue Swirl wrote:
On Sun, May 22, 2011 at 2:36 PM, Avi Kivity<a...@redhat.com> wrote:
> On 05/22/2011 12:32 PM, Blue Swirl wrote:
>>
>> >> > +void memory_region_add_coalescing(MemoryRegion *mr,
>> >> > + target_phys_addr_t offset,
>> >> > + target_phys_addr_t size);
>> >> > +/* Disable MMIO coalescing for the region. */
>> >> > +void memory_region_clear_coalescing(MemoryRegion *mr);
>> >>
>> >> Perhaps the interface could be more generic, like
>> >> +void memory_region_set_property(MemoryRegion *mr, unsigned flags);
>> >> +void memory_region_clear_property(MemoryRegion *mr, unsigned flags);
>> >>
>> >
>> > Coalescing is a complex property, not just a boolean attribute. We
>> > probably
>> > will have a number of boolean attributes later, though.
>>
>> But what is the difference between adding coalescing to an area and
>> setting the bit property 'coalescing' to an area? At least what you
>> propose now is not so complex that it couldn't be handled as a single
>> bit.
>
> Look at the API - add_coalescing() sets the coalescing property on a
> subrange of the memory region, not the entire region.
Right, but doesn't the same apply to any other properties, they may
apply to a full range or just a subrange?
We'll know when we have more properties. I expect most will be region-wide.
>
> Subregions are first-class regions. In fact all regions are subregions
> except the root.
Oh, I see now. Maybe the comments should describe this. Or perhaps the
terms should be something like 'bus/bridge/root' and 'region' instead
of 'region' and 'subregion'?
Problem is, memory_region_add_subregion() adds both sub-bridges and leaf
regions.
It's quite possible that BAR 0 will be a leaf region, and BAR 1 will be
a sub-bridge.
Can you suggest an alternative naming for the API?
> It's a tree of regions, each level adding an offset, clipping, and perhaps
> other attributes, with the leaves providing actual memory (mmio or RAM).
I thought that there are two classes of regions, like PCI device vs. a
single BAR.
It's true in a way, except the mapping is not 1:1.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
