mm/memblock.c: add new infrastructure to address the mem limit issue

In some cases, memblock is queried by kernel to determine whether a
specified address is RAM or not.  For example, the ACPI core needs this
information to determine which attributes to use when mapping ACPI
regions(acpi_os_ioremap).  Use of incorrect memory types can result in
faults, data corruption, or other issues.

Removing memory with memblock_enforce_memory_limit() throws away this
information, and so a kernel booted with 'mem=' may suffer from the
issues described above.  To avoid this, we need to keep those NOMAP
regions instead of removing all above the limit, which preserves the
information we need while preventing other use of those regions.

This patch adds new infrastructure to retain all NOMAP memblock regions
while removing others, to cater for this.

Link: http://lkml.kernel.org/r/1468475036-5852-2-git-send-email-dennis.chen@arm.com
Signed-off-by: Dennis Chen <dennis.chen@arm.com>
Acked-by: Steve Capper <steve.capper@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Tang Chen <tangchen@cn.fujitsu.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Rafael J. Wysocki <rafael@kernel.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Kaly Xin <kaly.xin@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index 6c14b6179727..2925da23505d 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -332,6 +332,7 @@ phys_addr_t memblock_mem_size(unsigned long limit_pfn);
 phys_addr_t memblock_start_of_DRAM(void);
 phys_addr_t memblock_end_of_DRAM(void);
 void memblock_enforce_memory_limit(phys_addr_t memory_limit);
+void memblock_mem_limit_remove_map(phys_addr_t limit);
 bool memblock_is_memory(phys_addr_t addr);
 int memblock_is_map_memory(phys_addr_t addr);
 int memblock_is_region_memory(phys_addr_t base, phys_addr_t size);