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From: Greg KH on 11 Aug 2010 20:40
2.6.32-stable review patch. If anyone has any objections, please let us know.

------------------

From: Shaohui Zheng <shaohui.zheng(a)intel.com>

commit ea0854170c95245a258b386c7a9314399c949fe0 upstream.

Newly added memory can not be accessed via /dev/mem, because we do not
update the variables high_memory, max_pfn and max_low_pfn.

Add a function update_end_of_memory_vars() to update these variables for
64-bit kernels.

[akpm(a)linux-foundation.org: simplify comment]
Signed-off-by: Shaohui Zheng <shaohui.zheng(a)intel.com>
Cc: Andi Kleen <ak(a)linux.intel.com>
Cc: Li Haicheng <haicheng.li(a)intel.com>
Reviewed-by: Wu Fengguang <fengguang.wu(a)intel.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu(a)jp.fujitsu.com>
Cc: Ingo Molnar <mingo(a)elte.hu>
Cc: Thomas Gleixner <tglx(a)linutronix.de>
Cc: "H. Peter Anvin" <hpa(a)zytor.com>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds(a)linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh(a)suse.de>

---
arch/x86/mm/init_64.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)

--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -49,6 +49,7 @@
#include <asm/numa.h>
#include <asm/cacheflush.h>
#include <asm/init.h>
+#include <linux/bootmem.h>

static unsigned long dma_reserve __initdata;

@@ -615,6 +616,21 @@ void __init paging_init(void)
*/
#ifdef CONFIG_MEMORY_HOTPLUG
/*
+ * After memory hotplug the variables max_pfn, max_low_pfn and high_memory need
+ * updating.
+ */
+static void update_end_of_memory_vars(u64 start, u64 size)
+{
+ unsigned long end_pfn = PFN_UP(start + size);
+
+ if (end_pfn > max_pfn) {
+ max_pfn = end_pfn;
+ max_low_pfn = end_pfn;
+ high_memory = (void *)__va(max_pfn * PAGE_SIZE - 1) + 1;
+ }
+}
+
+/*
* Memory is added always to NORMAL zone. This means you will never get
* additional DMA/DMA32 memory.
*/
@@ -633,6 +649,9 @@ int arch_add_memory(int nid, u64 start,
ret = __add_pages(nid, zone, start_pfn, nr_pages);
WARN_ON_ONCE(ret);

+ /* update max_pfn, max_low_pfn and high_memory */
+ update_end_of_memory_vars(start, size);
+
return ret;
}
EXPORT_SYMBOL_GPL(arch_add_memory);


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