Skip to contentSkip to conversation

Memory-Hotplug: Fix the bug on interface /dev/mem for 64-bit kernel

PATCH RESEND In review Shaohui Zheng 2 participants 3 messages Feb 1, 2010

Subsystems (3)
Memory management x86 x86 MM
lore
Share & tools
lore

Shaohui Zheng

author
#0 lore raw

PATCH RESEND v4 1/1 Memory-Hotplug: Fix the bug on interface /dev/mem for 64-bit kernel

Send the v4 patch to mailing list.

changelog:
v1: add memory range to e820 table, and update the varibles max_pfn/max_low_pfn/high_memory
Peter[hpa]: memory hotplug make sense on 32-bit kernel for virtual environment.
Andi[ak]: No VM supports it currently, and 64bit is the important part for hotplug Fengguang[wfg]: some review comments on function naming
v2: rename function update_pfn to update_end_of_memory_vars
KAMEZAWA[kame]: e820map is considerted to be stable, read-only after boot.
Fengguang[wfg]: rewrite function page_is_ram, make it friendly for hotplug.
v3: keep the old e820map, update the varible max_pfn, high_memory only
KAMEZAWA[kame]: suggest to use memory hotplug notifier. If it's allowed, it will
be cleaner.
Fengguang[wfg]: notifier is for _outsider_ subsystems. It smells a bit overkill to do
notifier _inside_ the hotplug code.
Fengguang[wfg]: suggest to update max_pfn/max_low_pfn/high_memory in arch/x86/mm/init_64.c:
arch_add_memory() now, for X86_64.
Later on we can add code to arch/x86/mm/init_32.c:arch_add_memory() for X86_32.
v4: update max_pfn/max_low_pfn/high_memory in arch/x86/mm/init_64.c:arch_add_memory() for x86_64,
and resent it to mailing list, since fengguang's page_is_ram patch was accepted,

Memory-Hotplug: Fix the bug on interface /dev/mem for 64-bit kernel

The new added memory can not be access by interface /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 kernel.

CC Andi Kleen <[email protected]>
CC Li Haicheng <[email protected]>
Reviewed-by Wu Fengguang <[email protected]>
Reviewed-by KAMEZAWA Hiroyuki <[email protected]>
Signed-off-by Shaohui Zheng <[email protected]>
arch/x86/mm/init_64.c +16 -1
index 5a4398a..acfc01a 100644
@@ -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;
 

@@ -614,6 +615,21 @@ void __init paging_init(void)
  * Memory hotplug specific functions
  */
 #ifdef CONFIG_MEMORY_HOTPLUG
+/**
+ * After memory hotplug, the variable max_pfn, max_low_pfn and high_memory will
+ * be affected, it will be updated in this function.
+ */
+static inline void __meminit update_end_of_memory_vars(u64 start,
+		u64 size)
+{
+	unsigned long end_pfn = PFN_UP(start + size);
+
+	if (end_pfn > max_pfn) {
+		max_low_pfn = max_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, u64 size)
 	ret = __add_pages(nid, zone, start_pfn, nr_pages);
 	WARN_ON_ONCE(ret);
--

Thanks & Regards,
Shaohuki

Memory-Hotplug: Fix the bug on interface /dev/mem for 64-bit kernel

The new added memory can not be access by interface /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 kernel.

CC Andi Kleen <[email protected]>
CC Li Haicheng <[email protected]>
Reviewed-by Wu Fengguang <[email protected]>
Reviewed-by KAMEZAWA Hiroyuki <[email protected]>
Signed-off-by Shaohui Zheng <[email protected]>
arch/x86/mm/init_64.c +19 -0
index 5a4398a..acfc01a 100644
@@ -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;
 

@@ -614,6 +615,21 @@ void __init paging_init(void)
  * Memory hotplug specific functions
  */
 #ifdef CONFIG_MEMORY_HOTPLUG
+/**
+ * After memory hotplug, the variable max_pfn, max_low_pfn and high_memory will
+ * be affected, it will be updated in this function.
+ */
+static inline void __meminit update_end_of_memory_vars(u64 start,
+		u64 size)
+{
+	unsigned long end_pfn = PFN_UP(start + size);
+
+	if (end_pfn > max_pfn) {
+		max_low_pfn = max_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, u64 size)
 	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);
#1 lore raw

Shaohui,

Some style nitpicks..

Quoted 2 lines

#ifdef CONFIG_MEMORY_HOTPLUG
+/**

Should use /* here.

Quoted 4 lines

+ * After memory hotplug, the variable max_pfn, max_low_pfn and high_memory will
+ * be affected, it will be updated in this function.
+ */
+static inline void __meminit update_end_of_memory_vars(u64 start,

The "inline" and "__meminit" are both redundant here.

Review

Quoted 1 line
(quoted diff) +1 -0
+		max_low_pfn = max_pfn = end_pfn;

One assignment per line is preferred.

Thanks,
Fengguang

author Reviewed-by Wu Fengguang Reviewed-by KAMEZAWA Hiroyuki Reviewed-by Wu Fengguang Reviewed-by KAMEZAWA Hiroyuki
#2 lore raw
Quoted 8 lines · Wu Fengguang

Shaohui,

Some style nitpicks..

Quoted 2 lines

#ifdef CONFIG_MEMORY_HOTPLUG
+/**

Should use /* here.

Agree.

Quoted 7 lines
Quoted 5 lines

+ * After memory hotplug, the variable max_pfn, max_low_pfn and high_memory will
+ * be affected, it will be updated in this function.
+ */
+static inline void __meminit update_end_of_memory_vars(u64 start,

The "inline" and "__meminit" are both redundant here.

will remove both.

Quoted 4 lines

Review

Quoted 2 lines
(quoted diff) +1 -0
+		max_low_pfn = max_pfn = end_pfn;

One assignment per line is preferred.

will change to 2 statements.

Quoted 3 lines

Thanks,
Fengguang

Memory-Hotplug: Fix the bug on interface /dev/mem for 64-bit kernel

The new added memory can not be access by interface /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 kernel.

CC Andi Kleen <[email protected]>
CC Li Haicheng <[email protected]>
Reviewed-by Wu Fengguang <[email protected]>
Reviewed-by KAMEZAWA Hiroyuki <[email protected]>
Signed-off-by Shaohui Zheng <[email protected]>
arch/x86/mm/init_64.c +19 -0
index 5198b9b..e1c9202 100644
@@ -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;
 

@@ -616,6 +617,21 @@ void __init paging_init(void)
  */
 #ifdef CONFIG_MEMORY_HOTPLUG
 /*
+ * After memory hotplug, the variables max_pfn, max_low_pfn and high_memory will
+ * be affected, they will be updated in this function.
+ */
+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.
  */

@@ -634,6 +650,9 @@ int arch_add_memory(int nid, u64 start, u64 size)
 	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);
Signature · 2 lines
Thanks & Regards,
Shaohui

Memory-Hotplug: Fix the bug on interface /dev/mem for 64-bit kernel

The new added memory can not be access by interface /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 kernel.

CC Andi Kleen <[email protected]>
CC Li Haicheng <[email protected]>
Reviewed-by Wu Fengguang <[email protected]>
Reviewed-by KAMEZAWA Hiroyuki <[email protected]>
Signed-off-by Shaohui Zheng <[email protected]>
arch/x86/mm/init_64.c +19 -0
index 5198b9b..e1c9202 100644
@@ -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;
 

@@ -616,6 +617,21 @@ void __init paging_init(void)
  */
 #ifdef CONFIG_MEMORY_HOTPLUG
 /*
+ * After memory hotplug, the variables max_pfn, max_low_pfn and high_memory will
+ * be affected, they will be updated in this function.
+ */
+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.
  */

@@ -634,6 +650,9 @@ int arch_add_memory(int nid, u64 start, u64 size)
 	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);