Re: [Qemu-devel] memory: Why subpage is introduced?

[Avi Kivity <avi@redhat.com>]

On 12/22/2011 01:24 PM, Zhi Yong Wu wrote:
> >
> >> 2.) How to render MemoryRegion into one disjoint flatrange list? That
> >> rendering function is a bit difficult to understand. Can anyone simply
> >> explain it?
> >
> > What exactly don't you understand?
> 1.) e.g. some fields such as offset_in_region, terminates, offset in
> MemoryRegion struct. What are separately their meanings?

Well, read the code, it's not that complicated.  Afterwards you can add
documentation based on your findings.

> 2.)  render_memory_region(), how does it render one MemoryRegion into
> the global view flatview? Can you simply explain this function's
> algorithm logic?

Again, what can I say that the code doesn't?  It recursively descends
the hierarchy and finds out which region goes where.

Also read docs/memory.txt

>
> >
> >>
> >> 3.) What are separately the meanings of these flags? such as
> >> IO_MEM_RAM, IO_MEM_ROM, IO_MEM_UNASSIGNED, IO_MEM_*, IO_MEM_ROMD, and
> >> IO_MEM_SUBPAGE.
> >
> > RAM = RAM
> > ROM = ROM
> > UNASSIGNED = nothing handles this range
> > ROMD = ROM when read, device (i.e. callbacks) when written
> > SUBPAGE = dispatch using the lower address bits to obtain final I/O handler.
> thanks.
>
> By the way, if you are available, can you simply explain what is the
> relationship among them and how they work together? such as
> MemoryRegion, RamBlock, PhysPageDesc, and MemorySlot.
>

Sorry, it's a long and complicated story that is changing now.  You'll
have to educate yourself mostly.

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