modules_headroom is a misleading name as it applies strictly to mod[0] only, and the movement loop is deeply unintuitive and completely undocumented.
Provide help to whomever needs to look at this code next. Signed-off-by: Andrew Cooper <[email protected]> --- CC: Jan Beulich <[email protected]> CC: Roger Pau Monné <[email protected]> CC: Stefano Stabellini <[email protected]> CC: Daniel Smith <[email protected]> CC: Christopher Clark <[email protected]> --- xen/arch/x86/setup.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c index caf235c6286d..59907fae095f 100644 --- a/xen/arch/x86/setup.c +++ b/xen/arch/x86/setup.c @@ -1432,6 +1432,11 @@ void asmlinkage __init noreturn __start_xen(unsigned long mbi_p) /* Is the region suitable for relocating the multiboot modules? */ for ( j = mbi->mods_count - 1; j >= 0; j-- ) { + /* + * 'headroom' is a guess for the decompressed size and + * decompressor overheads of mod[0] (the dom0 kernel). When we + * move mod[0], we incorperate this as extra space at the start. + */ unsigned long headroom = j ? 0 : modules_headroom; unsigned long size = PAGE_ALIGN(headroom + mod[j].mod_end); -- 2.30.2
