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authorRussell King <rmk+kernel@arm.linux.org.uk>2013-07-17 17:53:04 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2013-07-22 14:30:00 +0100
commitc65b7e98b4edce7faf534154b28eae8fb579144b (patch)
tree141bcf20050c4451945fe0dfe642ce6318dcdf44 /arch/arm/mm/mmu.c
parentbf3f0f332f76a85ff3a0b393aaded5a8533769c0 (diff)
ARM: 7785/1: mm: restrict early_alloc to section-aligned memory
When map_lowmem() runs, and processes a memory bank whose start or end is not section-aligned, memory must be allocated to store the 2nd-level page tables. Those allocations are made by calling memblock_alloc(). At this point, the only memory that is free *and* mapped is memory which has already been mapped by map_lowmem() itself. For this reason, we must calculate the first point at which map_lowmem() will need to allocate memory, and set the memblock allocation limit to a lower address, so that memblock_alloc() is guaranteed to return memory that is already mapped. This patch enhances sanity_check_meminfo() to calculate that memory address, and pass it to memblock_set_current_limit(), rather than just assuming the limit is arm_lowmem_limit. The algorithm applied is: * Default memblock_limit to arm_lowmem_limit in the absence of any other limit; arm_lowmem_limit is the highest memory that is mapped by map_lowmem(). * While walking the list of memblocks, if the start of a block is not aligned, 2nd-level page tables will need to be allocated to map the first few pages of the block. Hence, the memblock_limit must be before the start of the block. * Similarly, if the end of any block is not aligned, 2nd-level page tables will need to be allocated to map the last few pages of the block. Hence, the memblock_limit must point at the end of the block, rounded down to section-alignment. * The memory blocks are assumed to be sorted in address order, so the first unaligned block start or end is used to set the limit. With this algorithm, the start or end of almost any bank can be non- section-aligned. The only exception is that the start of bank 0 must be section-aligned, since otherwise memory would need to be allocated when mapping the start of bank 0, which occurs before any free memory is mapped. [swarren, wrote commit description, rewrote calculation of memblock_limit] Signed-off-by: Stephen Warren <swarren@nvidia.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/mm/mmu.c')
-rw-r--r--arch/arm/mm/mmu.c43
1 files changed, 38 insertions, 5 deletions
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 4f56617a2392..b3fdb63783e3 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -989,6 +989,7 @@ phys_addr_t arm_lowmem_limit __initdata = 0;
void __init sanity_check_meminfo(void)
{
+ phys_addr_t memblock_limit = 0;
int i, j, highmem = 0;
phys_addr_t vmalloc_limit = __pa(vmalloc_min - 1) + 1;
@@ -1052,9 +1053,32 @@ void __init sanity_check_meminfo(void)
bank->size = size_limit;
}
#endif
- if (!bank->highmem && bank->start + bank->size > arm_lowmem_limit)
- arm_lowmem_limit = bank->start + bank->size;
+ if (!bank->highmem) {
+ phys_addr_t bank_end = bank->start + bank->size;
+ if (bank_end > arm_lowmem_limit)
+ arm_lowmem_limit = bank_end;
+
+ /*
+ * Find the first non-section-aligned page, and point
+ * memblock_limit at it. This relies on rounding the
+ * limit down to be section-aligned, which happens at
+ * the end of this function.
+ *
+ * With this algorithm, the start or end of almost any
+ * bank can be non-section-aligned. The only exception
+ * is that the start of the bank 0 must be section-
+ * aligned, since otherwise memory would need to be
+ * allocated when mapping the start of bank 0, which
+ * occurs before any free memory is mapped.
+ */
+ if (!memblock_limit) {
+ if (!IS_ALIGNED(bank->start, SECTION_SIZE))
+ memblock_limit = bank->start;
+ else if (!IS_ALIGNED(bank_end, SECTION_SIZE))
+ memblock_limit = bank_end;
+ }
+ }
j++;
}
#ifdef CONFIG_HIGHMEM
@@ -1079,7 +1103,18 @@ void __init sanity_check_meminfo(void)
#endif
meminfo.nr_banks = j;
high_memory = __va(arm_lowmem_limit - 1) + 1;
- memblock_set_current_limit(arm_lowmem_limit);
+
+ /*
+ * Round the memblock limit down to a section size. This
+ * helps to ensure that we will allocate memory from the
+ * last full section, which should be mapped.
+ */
+ if (memblock_limit)
+ memblock_limit = round_down(memblock_limit, SECTION_SIZE);
+ if (!memblock_limit)
+ memblock_limit = arm_lowmem_limit;
+
+ memblock_set_current_limit(memblock_limit);
}
static inline void prepare_page_table(void)
@@ -1276,8 +1311,6 @@ void __init paging_init(struct machine_desc *mdesc)
{
void *zero_page;
- memblock_set_current_limit(arm_lowmem_limit);
-
build_mem_type_table();
prepare_page_table();
map_lowmem();