memblock: add memblock_cap_memory_range()

Add memblock_cap_memory_range() which will remove all the memblock regions
except the memory range specified in the arguments. In addition, rework is
done on memblock_mem_limit_remove_map() to re-implement it using
memblock_cap_memory_range().

This function, like memblock_mem_limit_remove_map(), will not remove
memblocks with MEMMAP_NOMAP attribute as they may be mapped and accessed
later as "device memory."
See the commit a571d4eb55d8 ("mm/memblock.c: add new infrastructure to
address the mem limit issue").

This function is used, in a succeeding patch in the series of arm64 kdump
suuport, to limit the range of usable memory, or System RAM, on crash dump
kernel.
(Please note that "mem=" parameter is of little use for this purpose.)

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Dennis Chen <dennis.chen@arm.com>
Cc: linux-mm@kvack.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index e82daff..4ce24a3 100644 (file)
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -336,6 +336,7 @@ 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_cap_memory_range(phys_addr_t base, phys_addr_t size);
 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);

diff --git a/mm/memblock.c b/mm/memblock.c
index 2f4ca81..b049c9b 100644 (file)
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -1543,11 +1543,37 @@ void __init memblock_enforce_memory_limit(phys_addr_t limit)
                              (phys_addr_t)ULLONG_MAX);
 }
 
+void __init memblock_cap_memory_range(phys_addr_t base, phys_addr_t size)
+{
+       int start_rgn, end_rgn;
+       int i, ret;
+
+       if (!size)
+               return;
+
+       ret = memblock_isolate_range(&memblock.memory, base, size,
+                                               &start_rgn, &end_rgn);
+       if (ret)
+               return;
+
+       /* remove all the MAP regions */
+       for (i = memblock.memory.cnt - 1; i >= end_rgn; i--)
+               if (!memblock_is_nomap(&memblock.memory.regions[i]))
+                       memblock_remove_region(&memblock.memory, i);
+
+       for (i = start_rgn - 1; i >= 0; i--)
+               if (!memblock_is_nomap(&memblock.memory.regions[i]))
+                       memblock_remove_region(&memblock.memory, i);
+
+       /* truncate the reserved regions */
+       memblock_remove_range(&memblock.reserved, 0, base);
+       memblock_remove_range(&memblock.reserved,
+                       base + size, (phys_addr_t)ULLONG_MAX);
+}
+
 void __init memblock_mem_limit_remove_map(phys_addr_t limit)
 {
-       struct memblock_type *type = &memblock.memory;
        phys_addr_t max_addr;
-       int i, ret, start_rgn, end_rgn;
 
        if (!limit)
                return;
@@ -1558,19 +1584,7 @@ void __init memblock_mem_limit_remove_map(phys_addr_t limit)
        if (max_addr == (phys_addr_t)ULLONG_MAX)
                return;
 
-       ret = memblock_isolate_range(type, max_addr, (phys_addr_t)ULLONG_MAX,
-                               &start_rgn, &end_rgn);
-       if (ret)
-               return;
-
-       /* remove all the MAP regions above the limit */
-       for (i = end_rgn - 1; i >= start_rgn; i--) {
-               if (!memblock_is_nomap(&type->regions[i]))
-                       memblock_remove_region(type, i);
-       }
-       /* truncate the reserved regions */
-       memblock_remove_range(&memblock.reserved, max_addr,
-                             (phys_addr_t)ULLONG_MAX);
+       memblock_cap_memory_range(0, max_addr);
 }
 
 static int __init_memblock memblock_search(struct memblock_type *type, phys_addr_t addr)