x86, memblock: Use memblock_memory_size()/memblock_free_memory_size() to get correct dma_reserve

memblock_memory_size() will return memory size in memblock.memory.region.
memblock_free_memory_size() will return free memory size in memblock.memory.region.

So We can get exact reseved size in specified range.

Set the size right after initmem_init(), because later bootmem API will
get area above 16M. (except some fallback).

Later after we remove the bootmem, We could call that just before paging_init().

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/x86/include/asm/e820.h

@@ -117,6 +117,8 @@ extern unsigned long e820_end_of_low_ram_pfn(void);
 extern u64 early_reserve_e820(u64 startt, u64 sizet, u64 align);
 
 void memblock_x86_fill(void);
+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);

arch/x86/kernel/e820.c

@@ -1105,3 +1105,19 @@ void __init memblock_x86_fill(void)
 	memblock_analyze();
 	memblock_dump_all();
 }
+
+void __init memblock_find_dma_reserve(void)
+{
+#ifdef CONFIG_X86_64
+	u64 free_size_pfn;
+	u64 mem_size_pfn;
+	/*
+	 * 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
+	 */
+	mem_size_pfn = memblock_x86_memory_in_range(0, MAX_DMA_PFN << PAGE_SHIFT) >> PAGE_SHIFT;
+	free_size_pfn = memblock_x86_free_memory_in_range(0, MAX_DMA_PFN << PAGE_SHIFT) >> PAGE_SHIFT;
+	set_dma_reserve(mem_size_pfn - free_size_pfn);
+#endif
+}

arch/x86/kernel/setup.c

@@ -1013,6 +1013,7 @@ void __init setup_arch(char **cmdline_p)
 #endif
 
 	initmem_init(0, max_pfn, acpi, k8);
+	memblock_find_dma_reserve();
 #ifndef CONFIG_NO_BOOTMEM
 	memblock_x86_to_bootmem(0, max_low_pfn<<PAGE_SHIFT);
 #endif

arch/x86/mm/init_64.c

@@ -53,8 +53,6 @@
 #include <asm/init.h>
 #include <linux/bootmem.h>
 
-static unsigned long dma_reserve __initdata;
-
 static int __init parse_direct_gbpages_off(char *arg)
 {
 	direct_gbpages = 0;
@@ -821,11 +819,6 @@ int __init reserve_bootmem_generic(unsigned long phys, unsigned long len,
 
 	reserve_bootmem(phys, len, flags);
 
-	if (phys+len <= MAX_DMA_PFN*PAGE_SIZE) {
-		dma_reserve += len / PAGE_SIZE;
-		set_dma_reserve(dma_reserve);
-	}
-
 	return 0;
 }
 #endif