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authorH. Peter Anvin <hpa@linux.intel.com>2013-02-27 12:46:40 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-03-04 06:09:03 +0800
commit93b6b299f7a97a8ce2f8ab7b14195f8d2d131905 (patch)
tree356573809b3f31e742178d20611174010cde06d9 /arch/sh/mm
parent834f139f1613ba0ca3239a6a12be97c70698f189 (diff)
x86: Make sure we can boot in the case the BDA contains pure garbage
commit 7c10093692ed2e6f318387d96b829320aa0ca64c upstream. 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 <dvhart@linux.intel.com> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Cc: Matt Fleming <matt.fleming@intel.com> Link: http://lkml.kernel.org/n/tip-oebml055yyfm8yxmria09rja@git.kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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