[RFC PATCH]: ACPI: Automatically online hot-added memory

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New sockets have on-die memory controllers.  This means that in certain
HW configurations the memory behind the socket comes and goes as the socket
is physically enabled and disabled.

Since the cpu bringup code does on node memory allocations, the memory on the
added socket must be onlined first.

Add a .config option to automatically online hot added memory, and enable it
in the acpi memory add path.

Signed-off-by: Prarit Bhargava <prarit@xxxxxxxxxx>

diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index 93d2c79..dece6bd 100644
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -350,6 +350,14 @@ config ACPI_HOTPLUG_MEMORY
 	  To compile this driver as a module, choose M here:
 	  the module will be called acpi_memhotplug.
 
+config ACPI_HOTPLUG_MEMORY_AUTO_ONLINE
+	bool "Automatically online hotplugged memory"
+	depends on ACPI_HOTPLUG_MEMORY
+	default n
+	help
+	  This forces memory that is brought into service by ACPI
+	  to be automatically onlined.
+
 config ACPI_SBS
 	tristate "Smart Battery System"
 	depends on X86
diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
index 3597d73..9814c50 100644
--- a/drivers/acpi/acpi_memhotplug.c
+++ b/drivers/acpi/acpi_memhotplug.c
@@ -30,6 +30,7 @@
 #include <linux/init.h>
 #include <linux/types.h>
 #include <linux/memory_hotplug.h>
+#include <linux/memory.h>
 #include <acpi/acpi_drivers.h>
 
 #define ACPI_MEMORY_DEVICE_CLASS		"memory"
@@ -252,6 +253,19 @@ static int acpi_memory_enable_device(struct acpi_memory_device *mem_device)
 		result = add_memory(node, info->start_addr, info->length);
 		if (result)
 			continue;
+#ifdef CONFIG_ACPI_HOTPLUG_MEMORY_AUTO_ONLINE
+		/*
+		 * New processors require memory to be online before cpus.
+		 * No notifications are required here as "we" are the only
+		 * ones who know about the new memory right now.
+		 */
+		result = online_pages(info->start_addr >> PAGE_SHIFT,
+				      info->length >> PAGE_SHIFT);
+		if (!result)
+			set_memory_state(info->start_addr, MEM_ONLINE);
+		else
+			printk("Memory online failed.\n");
+#endif
 		info->enabled = 1;
 		num_enabled++;
 	}
diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 2f86915..fb465d5 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -510,6 +510,20 @@ int remove_memory_block(unsigned long node_id, struct mem_section *section,
 }
 
 /*
+ * need an interface for the VM to mark sections on and offline when hot-adding
+ * memory.
+ */
+void set_memory_state(unsigned long addr, unsigned long state)
+{
+	struct mem_section *section;
+	struct memory_block *mem;
+
+	section = __pfn_to_section(addr >> PAGE_SHIFT);
+	mem = find_memory_block(section);
+	mem->state = state;
+}
+
+/*
  * need an interface for the VM to add new memory regions,
  * but without onlining it.
  */
diff --git a/include/linux/memory.h b/include/linux/memory.h
index 1adfe77..5d8d78c 100644
--- a/include/linux/memory.h
+++ b/include/linux/memory.h
@@ -112,6 +112,7 @@ extern int remove_memory_block(unsigned long, struct mem_section *, int);
 extern int memory_notify(unsigned long val, void *v);
 extern int memory_isolate_notify(unsigned long val, void *v);
 extern struct memory_block *find_memory_block(struct mem_section *);
+extern void set_memory_state(unsigned long, unsigned long);
 #define CONFIG_MEM_BLOCK_SIZE	(PAGES_PER_SECTION<<PAGE_SHIFT)
 enum mem_add_context { BOOT, HOTPLUG };
 #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */
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