linux/drivers/lguest
Rusty Russell 42b36cc0ce virtio: Force use of power-of-two for descriptor ring sizes
The virtio descriptor rings of size N-1 were nicely set up to be
aligned to an N-byte boundary.  But as Anthony Liguori points out, the
free-running indices used by virtio require that the sizes be a power
of 2, otherwise we get problems on wrap (demonstrated with lguest).

So we replace the clever "2^n-1" scheme with a simple "align to page
boundary" scheme: this means that all virtio rings take at least two
pages, but it's safer than guessing cache alignment.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2007-11-12 13:59:40 +11:00
..
x86 lguest: documentation update 2007-10-25 15:02:50 +10:00
core.c lguest: documentation update 2007-10-25 15:02:50 +10:00
hypercalls.c lguest: documentation update 2007-10-25 15:02:50 +10:00
interrupts_and_traps.c lguest: documentation update 2007-10-25 15:02:50 +10:00
Kconfig Remove old lguest bus and drivers. 2007-10-23 15:49:55 +10:00
lg.h lguest: documentation update 2007-10-25 15:02:50 +10:00
lguest_device.c virtio: Force use of power-of-two for descriptor ring sizes 2007-11-12 13:59:40 +11:00
lguest_user.c lguest: documentation update 2007-10-25 15:02:50 +10:00
Makefile Lguest support for Virtio 2007-10-23 15:49:56 +10:00
page_tables.c lguest: documentation update 2007-10-25 15:02:50 +10:00
README lguest: documentation I: Preparation 2007-07-26 11:35:16 -07:00
segments.c lguest: documentation update 2007-10-25 15:02:50 +10:00

Welcome, friend reader, to lguest.

Lguest is an adventure, with you, the reader, as Hero.  I can't think of many
5000-line projects which offer both such capability and glimpses of future
potential; it is an exciting time to be delving into the source!

But be warned; this is an arduous journey of several hours or more!  And as we
know, all true Heroes are driven by a Noble Goal.  Thus I offer a Beer (or
equivalent) to anyone I meet who has completed this documentation.

So get comfortable and keep your wits about you (both quick and humorous).
Along your way to the Noble Goal, you will also gain masterly insight into
lguest, and hypervisors and x86 virtualization in general.

Our Quest is in seven parts: (best read with C highlighting turned on)

I) Preparation
	- In which our potential hero is flown quickly over the landscape for a
	  taste of its scope.  Suitable for the armchair coders and other such
	  persons of faint constitution.

II) Guest
	- Where we encounter the first tantalising wisps of code, and come to
	  understand the details of the life of a Guest kernel.

III) Drivers
	- Whereby the Guest finds its voice and become useful, and our
	  understanding of the Guest is completed.

IV) Launcher
	- Where we trace back to the creation of the Guest, and thus begin our
	  understanding of the Host.

V) Host
	- Where we master the Host code, through a long and tortuous journey.
	  Indeed, it is here that our hero is tested in the Bit of Despair.

VI) Switcher
	- Where our understanding of the intertwined nature of Guests and Hosts
	  is completed.

VII) Mastery
	- Where our fully fledged hero grapples with the Great Question:
	  "What next?"

make Preparation!
Rusty Russell.