4 files changed, 48 insertions, 32 deletions
diff --git a/arch/x86/include/asm/e820/api.h b/arch/x86/include/asm/e820/api.h
index 01698548fbc8..7c9e4bb84059 100644
--- a/arch/x86/include/asm/e820/api.h
+++ b/arch/x86/include/asm/e820/api.h
@@ -22,7 +22,6 @@ extern unsigned long e820_end_of_ram_pfn(void);
 extern unsigned long e820_end_of_low_ram_pfn(void);
 extern u64  early_reserve_e820(u64 sizet, u64 align);
 extern void e820__memblock_setup(void);
-extern void memblock_find_dma_reserve(void);
 extern void finish_e820_parsing(void);
 extern void e820_reserve_resources(void);
 extern void e820_reserve_resources_late(void);
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index ffaefb24891c..2d8116136f3e 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -733,6 +733,7 @@ static inline int pgd_none(pgd_t pgd)
 extern int direct_gbpages;
 void init_mem_mapping(void);
 void early_alloc_pgt_buf(void);
+extern void memblock_find_dma_reserve(void);
 
 #ifdef CONFIG_X86_64
 /* Realmode trampoline initialization. */
diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 4a8d905226c9..5f8ba898e29d 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -1172,34 +1172,3 @@ void __init e820__memblock_setup(void)
 
 	memblock_dump_all();
 }
-
-void __init memblock_find_dma_reserve(void)
-{
-#ifdef CONFIG_X86_64
-	u64 nr_pages = 0, nr_free_pages = 0;
-	unsigned long start_pfn, end_pfn;
-	phys_addr_t start, end;
-	int i;
-	u64 u;
-
-	/*
-	 * need to find out used area below MAX_DMA_PFN
-	 * need to use memblock to get free size in [0, MAX_DMA_PFN]
-	 * at first, and assume boot_mem will not take below MAX_DMA_PFN
-	 */
-	for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, NULL) {
-		start_pfn = min(start_pfn, MAX_DMA_PFN);
-		end_pfn = min(end_pfn, MAX_DMA_PFN);
-		nr_pages += end_pfn - start_pfn;
-	}
-
-	for_each_free_mem_range(u, NUMA_NO_NODE, MEMBLOCK_NONE, &start, &end, NULL) {
-		start_pfn = min_t(unsigned long, PFN_UP(start), MAX_DMA_PFN);
-		end_pfn = min_t(unsigned long, PFN_DOWN(end), MAX_DMA_PFN);
-		if (start_pfn < end_pfn)
-			nr_free_pages += end_pfn - start_pfn;
-	}
-
-	set_dma_reserve(nr_pages - nr_free_pages);
-#endif
-}
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index b7b4ad569d13..922671d3af85 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -724,6 +724,53 @@ void __init free_initrd_mem(unsigned long start, unsigned long end)
 }
 #endif
 
+/*
+ * Calculate the precise size of the DMA zone (first 16 MB of RAM),
+ * and pass it to the MM layer - to help it set zone watermarks more
+ * accurately.
+ *
+ * Done on 64-bit systems only for the time being, although 32-bit systems
+ * might benefit from this as well.
+ */
+void __init memblock_find_dma_reserve(void)
+{
+#ifdef CONFIG_X86_64
+	u64 nr_pages = 0, nr_free_pages = 0;
+	unsigned long start_pfn, end_pfn;
+	phys_addr_t start_addr, end_addr;
+	int i;
+	u64 u;
+
+	/*
+	 * Iterate over all memory ranges (free and reserved ones alike),
+	 * to calculate the total number of pages in the first 16 MB of RAM:
+	 */
+	nr_pages = 0;
+	for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, NULL) {
+		start_pfn = min(start_pfn, MAX_DMA_PFN);
+		end_pfn   = min(end_pfn,   MAX_DMA_PFN);
+
+		nr_pages += end_pfn - start_pfn;
+	}
+
+	/*
+	 * Iterate over free memory ranges to calculate the number of free
+	 * pages in the DMA zone, while not counting potential partial
+	 * pages at the beginning or the end of the range:
+	 */
+	nr_free_pages = 0;
+	for_each_free_mem_range(u, NUMA_NO_NODE, MEMBLOCK_NONE, &start_addr, &end_addr, NULL) {
+		start_pfn = min_t(unsigned long, PFN_UP(start_addr), MAX_DMA_PFN);
+		end_pfn   = min_t(unsigned long, PFN_DOWN(end_addr), MAX_DMA_PFN);
+
+		if (start_pfn < end_pfn)
+			nr_free_pages += end_pfn - start_pfn;
+	}
+
+	set_dma_reserve(nr_pages - nr_free_pages);
+#endif
+}
+
 void __init zone_sizes_init(void)
 {
 	unsigned long max_zone_pfns[MAX_NR_ZONES];