mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2025-01-12 16:19:53 +00:00
5dea1c88ed
The Host used to create some page tables for the Guest to use at the top of Guest memory; it would then tell the Guest where this was. In particular, it created linear mappings for 0 and 0xC0000000 addresses because lguest used to switch to its real page tables quite late in boot. However, since d50d8fe19 Linux initialized boot page tables in head_32.S even before the "are we lguest?" boot jump. So, now we can simplify things: the Host pagetable code assumes 1:1 linear mapping until it first calls the LHCALL_NEW_PGTABLE hypercall, which we now do before we reach C code. This also means that the Host doesn't need to know anything about the Guest's PAGE_OFFSET. (Non-Linux guests might not even have such a thing). Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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.