Re: AMAP_SHARED (was Re: XIP)

[Masao Uebayashi <uebayasi%tombi.co.jp@localhost>]

I have found that XIP is very similar to AMAP_SHARED, at the point
where XIP supports "write" operation.

Imagine a FlashROM page is XIP'ed and shared as vnode by processes.
The user rewrite the firmware written onto the FlashROM.  To keep
processes running, we need to copy the XIP pages into RAM (page
cache), put those pages into the vnode, then notify processes to
update their VA.  This is another kind of COW, done in another
layer.

Of course, we need PV tracking here.