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

[Avi Kivity]

On 12/21/2011 02:09 PM, Zhi Yong Wu wrote:
> HI,
>
> For memory management, i have several questions as below:
>
> 1.) Why is subpage introduced? what is its goal?

A TLB entry spans one page; a subpage is a way of dispatching accesses
through that tlb entry to various memory regions.

> 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?

>
> 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.

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