From: H. Peter Anvin Date: Wed, 27 Feb 2013 20:46:40 +0000 (-0800) Subject: x86: Make sure we can boot in the case the BDA contains pure garbage X-Git-Tag: v3.9-rc1~48^2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7c10093692ed2e6f318387d96b829320aa0ca64c;p=pandora-kernel.git x86: Make sure we can boot in the case the BDA contains pure garbage On non-BIOS platforms it is possible that the BIOS data area contains garbage instead of being zeroed or something equivalent (firmware people: we are talking of 1.5K here, so please do the sane thing.) We need on the order of 20-30K of low memory in order to boot, which may grow up to < 64K in the future. We probably want to avoid the lowest of the low memory. At the same time, it seems extremely unlikely that a legitimate EBDA would ever reach down to the 128K (which would require it to be over half a megabyte in size.) Thus, pick 128K as the cutoff for "this is insane, ignore." We may still end up reserving a bunch of extra memory on the low megabyte, but that is not really a major issue these days. In the worst case we lose 512K of RAM. This code really should be merged with trim_bios_range() in arch/x86/kernel/setup.c, but that is a bigger patch for a later merge window. Reported-by: Darren Hart Signed-off-by: H. Peter Anvin Cc: Matt Fleming Cc: Link: http://lkml.kernel.org/n/tip-oebml055yyfm8yxmria09rja@git.kernel.org --- Reading git-diff-tree failed