[PATCH 1/2 2.6.31-rc5 REPOST] init: set nr_cpu_ids before setup_per_cpu_areas()

[PATCH 1/2 2.6.31-rc5 REPOST] init: set nr_cpu_ids before setup_per_cpu_areas()

[Tejun Heo]

nr_cpu_ids is dependent only on cpu_possible_map and
setup_per_cpu_areas() already depends on cpu_possible_map and will use
nr_cpu_ids.  Initialize nr_cpu_ids before setting up percpu areas.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
This is repost of the following two patches with sparclinux mailing
list cc'd because I couldn't get any response from David Miller.
Nothing has changed code-wise.

 http://thread.gmane.org/gmane.linux.kernel/867587

These two patches fix boot failure on sparc64 which happens if the
cpus don't have consecutive cpu numbers.

Thanks.

 init/main.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/init/main.c b/init/main.c
index 2c5ade7..2d9d6bd 100644
--- a/init/main.c
+++ b/init/main.c
@@ -584,8 +584,8 @@ asmlinkage void __init start_kernel(void)
 	setup_arch(&command_line);
 	mm_init_owner(&init_mm, &init_task);
 	setup_command_line(command_line);
-	setup_per_cpu_areas();
 	setup_nr_cpu_ids();
+	setup_per_cpu_areas();
 	smp_prepare_boot_cpu();	/* arch-specific boot-cpu hooks */

 	build_all_zonelists();
-- 
1.6.0.2

[PATCH 2/2 2.6.31-rc5 REPOST] percpu, sparc64: fix sparse possible cpu map handling

[Tejun Heo]

percpu code has been assuming num_possible_cpus() == nr_cpu_ids which
is incorrect if cpu_possible_map contains holes.  This causes percpu
code to access beyond allocated memories and vmalloc areas.  On a
sparc64 machine with cpus 0 and 2 (u60), this triggers the following
warning or fails boot.

 WARNING: at /devel/tj/os/work/mm/vmalloc.c:106 vmap_page_range_noflush+0x1f0/0x240()
 Modules linked in:
 Call Trace:
  [00000000004b17d0] vmap_page_range_noflush+0x1f0/0x240
  [00000000004b1840] map_vm_area+0x20/0x60
  [00000000004b1950] __vmalloc_area_node+0xd0/0x160
  [0000000000593434] deflate_init+0x14/0xe0
  [0000000000583b94] __crypto_alloc_tfm+0xd4/0x1e0
  [00000000005844f0] crypto_alloc_base+0x50/0xa0
  [000000000058b898] alg_test_comp+0x18/0x80
  [000000000058dad4] alg_test+0x54/0x180
  [000000000058af00] cryptomgr_test+0x40/0x60
  [0000000000473098] kthread+0x58/0x80
  [000000000042b590] kernel_thread+0x30/0x60
  [0000000000472fd0] kthreadd+0xf0/0x160
 ---[ end trace 429b268a213317ba ]---

This patch fixes generic percpu functions and sparc64
setup_per_cpu_areas() so that they handle sparse cpu_possible_map
properly.

Please note that on x86, cpu_possible_map() doesn't contain holes and
thus num_possible_cpus() == nr_cpu_ids and this patch doesn't cause
any behavior difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Ingo Molnar <mingo@elte.hu>
---
As written in the previous mail, this fixes rather critical boot
problem on sparc64.  Upon ack, I can get it through the percpu tree.
Not really sure who could ack this one other than David tho.  Anyone?

Thanks.

 arch/sparc/kernel/smp_64.c     |    4 ++--
 arch/x86/kernel/setup_percpu.c |   14 +++++++-------
 mm/percpu.c                    |   31 +++++++++++++++++++------------
 3 files changed, 28 insertions(+), 21 deletions(-)

diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c
index fa44eaf..3691907 100644
--- a/arch/sparc/kernel/smp_64.c
+++ b/arch/sparc/kernel/smp_64.c
@@ -1499,7 +1499,7 @@ void __init setup_per_cpu_areas(void)
 	dyn_size = pcpur_size - static_size - PERCPU_MODULE_RESERVE;


-	ptrs_size = PFN_ALIGN(num_possible_cpus() * sizeof(pcpur_ptrs[0]));
+	ptrs_size = PFN_ALIGN(nr_cpu_ids * sizeof(pcpur_ptrs[0]));
 	pcpur_ptrs = alloc_bootmem(ptrs_size);

 	for_each_possible_cpu(cpu) {
@@ -1514,7 +1514,7 @@ void __init setup_per_cpu_areas(void)

 	/* allocate address and map */
 	vm.flags = VM_ALLOC;
-	vm.size = num_possible_cpus() * PCPU_CHUNK_SIZE;
+	vm.size = nr_cpu_ids * PCPU_CHUNK_SIZE;
 	vm_area_register_early(&vm, PCPU_CHUNK_SIZE);

 	for_each_possible_cpu(cpu) {
diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c
index 29a3eef..07d8191 100644
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -165,7 +165,7 @@ static ssize_t __init setup_pcpu_lpage(size_t static_size, bool chosen)

 	if (!chosen) {
 		size_t vm_size = VMALLOC_END - VMALLOC_START;
-		size_t tot_size = num_possible_cpus() * PMD_SIZE;
+		size_t tot_size = nr_cpu_ids * PMD_SIZE;

 		/* on non-NUMA, embedding is better */
 		if (!pcpu_need_numa())
@@ -199,7 +199,7 @@ static ssize_t __init setup_pcpu_lpage(size_t static_size, bool chosen)
 	dyn_size = pcpul_size - static_size - PERCPU_FIRST_CHUNK_RESERVE;

 	/* allocate pointer array and alloc large pages */
-	map_size = PFN_ALIGN(num_possible_cpus() * sizeof(pcpul_map[0]));
+	map_size = PFN_ALIGN(nr_cpu_ids * sizeof(pcpul_map[0]));
 	pcpul_map = alloc_bootmem(map_size);

 	for_each_possible_cpu(cpu) {
@@ -228,7 +228,7 @@ static ssize_t __init setup_pcpu_lpage(size_t static_size, bool chosen)

 	/* allocate address and map */
 	pcpul_vm.flags = VM_ALLOC;
-	pcpul_vm.size = num_possible_cpus() * PMD_SIZE;
+	pcpul_vm.size = nr_cpu_ids * PMD_SIZE;
 	vm_area_register_early(&pcpul_vm, PMD_SIZE);

 	for_each_possible_cpu(cpu) {
@@ -250,8 +250,8 @@ static ssize_t __init setup_pcpu_lpage(size_t static_size, bool chosen)
 				     PMD_SIZE, pcpul_vm.addr, NULL);

 	/* sort pcpul_map array for pcpu_lpage_remapped() */
-	for (i = 0; i < num_possible_cpus() - 1; i++)
-		for (j = i + 1; j < num_possible_cpus(); j++)
+	for (i = 0; i < nr_cpu_ids - 1; i++)
+		for (j = i + 1; j < nr_cpu_ids; j++)
 			if (pcpul_map[i].ptr > pcpul_map[j].ptr) {
 				struct pcpul_ent tmp = pcpul_map[i];
 				pcpul_map[i] = pcpul_map[j];
@@ -288,7 +288,7 @@ void *pcpu_lpage_remapped(void *kaddr)
 {
 	void *pmd_addr = (void *)((unsigned long)kaddr & PMD_MASK);
 	unsigned long offset = (unsigned long)kaddr & ~PMD_MASK;
-	int left = 0, right = num_possible_cpus() - 1;
+	int left = 0, right = nr_cpu_ids - 1;
 	int pos;

 	/* pcpul in use at all? */
@@ -377,7 +377,7 @@ static ssize_t __init setup_pcpu_4k(size_t static_size)
 	pcpu4k_nr_static_pages = PFN_UP(static_size);

 	/* unaligned allocations can't be freed, round up to page size */
-	pages_size = PFN_ALIGN(pcpu4k_nr_static_pages * num_possible_cpus()
+	pages_size = PFN_ALIGN(pcpu4k_nr_static_pages * nr_cpu_ids
 			       * sizeof(pcpu4k_pages[0]));
 	pcpu4k_pages = alloc_bootmem(pages_size);

diff --git a/mm/percpu.c b/mm/percpu.c
index b70f2ac..f772f02 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -8,12 +8,12 @@
  *
  * This is percpu allocator which can handle both static and dynamic
  * areas.  Percpu areas are allocated in chunks in vmalloc area.  Each
- * chunk is consisted of num_possible_cpus() units and the first chunk
- * is used for static percpu variables in the kernel image (special
- * boot time alloc/init handling necessary as these areas need to be
- * brought up before allocation services are running).  Unit grows as
- * necessary and all units grow or shrink in unison.  When a chunk is
- * filled up, another chunk is allocated.  ie. in vmalloc area
+ * chunk is consisted of nr_cpu_ids units and the first chunk is used
+ * for static percpu variables in the kernel image (special boot time
+ * alloc/init handling necessary as these areas need to be brought up
+ * before allocation services are running).  Unit grows as necessary
+ * and all units grow or shrink in unison.  When a chunk is filled up,
+ * another chunk is allocated.  ie. in vmalloc area
  *
  *  c0                           c1                         c2
  *  -------------------          -------------------        ------------
@@ -558,7 +558,7 @@ static void pcpu_free_area(struct pcpu_chunk *chunk, int freeme)
 static void pcpu_unmap(struct pcpu_chunk *chunk, int page_start, int page_end,
 		       bool flush_tlb)
 {
-	unsigned int last = num_possible_cpus() - 1;
+	unsigned int last = nr_cpu_ids - 1;
 	unsigned int cpu;

 	/* unmap must not be done on immutable chunk */
@@ -643,7 +643,7 @@ static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk, int off, int size,
  */
 static int pcpu_map(struct pcpu_chunk *chunk, int page_start, int page_end)
 {
-	unsigned int last = num_possible_cpus() - 1;
+	unsigned int last = nr_cpu_ids - 1;
 	unsigned int cpu;
 	int err;

@@ -1067,9 +1067,9 @@ size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
 					PFN_UP(size_sum));

 	pcpu_unit_size = pcpu_unit_pages << PAGE_SHIFT;
-	pcpu_chunk_size = num_possible_cpus() * pcpu_unit_size;
+	pcpu_chunk_size = nr_cpu_ids * pcpu_unit_size;
 	pcpu_chunk_struct_size = sizeof(struct pcpu_chunk)
-		+ num_possible_cpus() * pcpu_unit_pages * sizeof(struct page *);
+		+ nr_cpu_ids * pcpu_unit_pages * sizeof(struct page *);

 	if (dyn_size < 0)
 		dyn_size = pcpu_unit_size - static_size - reserved_size;
@@ -1248,7 +1248,7 @@ ssize_t __init pcpu_embed_first_chunk(size_t static_size, size_t reserved_size,
 	} else
 		pcpue_unit_size = max_t(size_t, pcpue_size, PCPU_MIN_UNIT_SIZE);

-	chunk_size = pcpue_unit_size * num_possible_cpus();
+	chunk_size = pcpue_unit_size * nr_cpu_ids;

 	pcpue_ptr = __alloc_bootmem_nopanic(chunk_size, PAGE_SIZE,
 					    __pa(MAX_DMA_ADDRESS));
@@ -1259,9 +1259,16 @@ ssize_t __init pcpu_embed_first_chunk(size_t static_size, size_t reserved_size,
 	}

 	/* return the leftover and copy */
-	for_each_possible_cpu(cpu) {
+	for (cpu = 0; cpu < nr_cpu_ids; cpu++) {
 		void *ptr = pcpue_ptr + cpu * pcpue_unit_size;

+		if (cpu_possible(cpu)) {
+			free_bootmem(__pa(ptr + pcpue_size),
+				     pcpue_unit_size - pcpue_size);
+			memcpy(ptr, __per_cpu_load, static_size);
+		} else
+			free_bootmem(__pa(ptr), pcpue_unit_size);
+
 		free_bootmem(__pa(ptr + pcpue_size),
 			     pcpue_unit_size - pcpue_size);
 		memcpy(ptr, __per_cpu_load, static_size);
-- 
1.6.0.2

Re: [PATCH 2/2 2.6.31-rc5 REPOST] percpu, sparc64: fix sparse possible cpu map handling

[Ingo Molnar]

* Tejun Heo <tj@kernel.org> wrote:

> percpu code has been assuming num_possible_cpus() == nr_cpu_ids which
> is incorrect if cpu_possible_map contains holes.  This causes percpu
> code to access beyond allocated memories and vmalloc areas.  On a
> sparc64 machine with cpus 0 and 2 (u60), this triggers the following
> warning or fails boot.
> 
>  WARNING: at /devel/tj/os/work/mm/vmalloc.c:106 vmap_page_range_noflush+0x1f0/0x240()
>  Modules linked in:
>  Call Trace:
>   [00000000004b17d0] vmap_page_range_noflush+0x1f0/0x240
>   [00000000004b1840] map_vm_area+0x20/0x60
>   [00000000004b1950] __vmalloc_area_node+0xd0/0x160
>   [0000000000593434] deflate_init+0x14/0xe0
>   [0000000000583b94] __crypto_alloc_tfm+0xd4/0x1e0
>   [00000000005844f0] crypto_alloc_base+0x50/0xa0
>   [000000000058b898] alg_test_comp+0x18/0x80
>   [000000000058dad4] alg_test+0x54/0x180
>   [000000000058af00] cryptomgr_test+0x40/0x60
>   [0000000000473098] kthread+0x58/0x80
>   [000000000042b590] kernel_thread+0x30/0x60
>   [0000000000472fd0] kthreadd+0xf0/0x160
>  ---[ end trace 429b268a213317ba ]---
> 
> This patch fixes generic percpu functions and sparc64
> setup_per_cpu_areas() so that they handle sparse cpu_possible_map
> properly.
> 
> Please note that on x86, cpu_possible_map() doesn't contain holes and
> thus num_possible_cpus() == nr_cpu_ids and this patch doesn't cause
> any behavior difference.
> 
> Signed-off-by: Tejun Heo <tj@kernel.org>
> Cc: David S. Miller <davem@davemloft.net>
> Cc: Ingo Molnar <mingo@elte.hu>
> ---
> As written in the previous mail, this fixes rather critical boot
> problem on sparc64.  Upon ack, I can get it through the percpu tree.
> Not really sure who could ack this one other than David tho.  Anyone?
> 
> Thanks.
> 
>  arch/sparc/kernel/smp_64.c     |    4 ++--
>  arch/x86/kernel/setup_percpu.c |   14 +++++++-------
>  mm/percpu.c                    |   31 +++++++++++++++++++------------
>  3 files changed, 28 insertions(+), 21 deletions(-)

for the x86 bits:

 Acked-by: Ingo Molnar <mingo@elte.hu>

Once Dave acks it i suspect you can send it to Linus directly?

	Ingo

Re: [PATCH 2/2 2.6.31-rc5 REPOST] percpu, sparc64: fix sparse possible cpu map handling

[Tejun Heo]

Ingo Molnar wrote:
> for the x86 bits:
> 
>  Acked-by: Ingo Molnar <mingo@elte.hu>
> 
> Once Dave acks it i suspect you can send it to Linus directly?

Yeap, I'll.

Thanks.

-- 
tejun

Re: [PATCH 2/2 2.6.31-rc5 REPOST] percpu, sparc64: fix sparse possible cpu map handling

[Tejun Heo]

Tejun Heo wrote:
> Ingo Molnar wrote:
>> for the x86 bits:
>>
>>  Acked-by: Ingo Molnar <mingo@elte.hu>
>>
>> Once Dave acks it i suspect you can send it to Linus directly?

Aieeeee, no response.  I'll push these two patches into linux-next
today.  Wait a few days and then push them to Linus.  :-(

Thanks.

-- 
tejun

Re: [PATCH 2/2 2.6.31-rc5 REPOST] percpu, sparc64: fix sparse possible cpu map handling

[David Miller]

From: Tejun Heo <tj@kernel.org>
Date: Wed, 12 Aug 2009 15:10:29 +0900

> Tejun Heo wrote:
>> Ingo Molnar wrote:
>>> for the x86 bits:
>>>
>>>  Acked-by: Ingo Molnar <mingo@elte.hu>
>>>
>>> Once Dave acks it i suspect you can send it to Linus directly?
> 
> Aieeeee, no response.

These patches look fine, and I've tested them also on my
Niagara-2 box.

Acked-by: David S. Miller <davem@davemloft.net>

Sorry for the delay :)

Re: [PATCH 2/2 2.6.31-rc5 REPOST] percpu, sparc64: fix sparse possible cpu map handling

[Tejun Heo]

David Miller wrote:
> From: Tejun Heo <tj@kernel.org>
> Date: Wed, 12 Aug 2009 15:10:29 +0900
> 
>> Tejun Heo wrote:
>>> Ingo Molnar wrote:
>>>> for the x86 bits:
>>>>
>>>>  Acked-by: Ingo Molnar <mingo@elte.hu>
>>>>
>>>> Once Dave acks it i suspect you can send it to Linus directly?
>> Aieeeee, no response.
> 
> These patches look fine, and I've tested them also on my
> Niagara-2 box.
> 
> Acked-by: David S. Miller <davem@davemloft.net>
> 
> Sorry for the delay :)

Great.  Oops, last review pass revealed a bug in the following chunk.

@@ -1259,9 +1259,16 @@ ssize_t __init pcpu_embed_first_chunk(size_t static_size, size_t reserved_size,
 	}

 	/* return the leftover and copy */
-	for_each_possible_cpu(cpu) {
+	for (cpu = 0; cpu < nr_cpu_ids; cpu++) {
 		void *ptr = pcpue_ptr + cpu * pcpue_unit_size;

+		if (cpu_possible(cpu)) {
+			free_bootmem(__pa(ptr + pcpue_size),
+				     pcpue_unit_size - pcpue_size);
+			memcpy(ptr, __per_cpu_load, static_size);
+		} else
+			free_bootmem(__pa(ptr), pcpue_unit_size);
+
 		free_bootmem(__pa(ptr + pcpue_size),
 			     pcpue_unit_size - pcpue_size);
 		memcpy(ptr, __per_cpu_load, static_size);

The if-else block should replace the original free_bootmem()/memcpy()
not added in front of it.  Fixed.  Will reply with updated patch.

Thanks.

-- 
tejun

[PATCH 2/2 2.6.31-rc5 UPDATED] percpu, sparc64: fix sparse possible cpu map handling

[Tejun Heo]

percpu code has been assuming num_possible_cpus() == nr_cpu_ids which
is incorrect if cpu_possible_map contains holes.  This causes percpu
code to access beyond allocated memories and vmalloc areas.  On a
sparc64 machine with cpus 0 and 2 (u60), this triggers the following
warning or fails boot.

 WARNING: at /devel/tj/os/work/mm/vmalloc.c:106 vmap_page_range_noflush+0x1f0/0x240()
 Modules linked in:
 Call Trace:
  [00000000004b17d0] vmap_page_range_noflush+0x1f0/0x240
  [00000000004b1840] map_vm_area+0x20/0x60
  [00000000004b1950] __vmalloc_area_node+0xd0/0x160
  [0000000000593434] deflate_init+0x14/0xe0
  [0000000000583b94] __crypto_alloc_tfm+0xd4/0x1e0
  [00000000005844f0] crypto_alloc_base+0x50/0xa0
  [000000000058b898] alg_test_comp+0x18/0x80
  [000000000058dad4] alg_test+0x54/0x180
  [000000000058af00] cryptomgr_test+0x40/0x60
  [0000000000473098] kthread+0x58/0x80
  [000000000042b590] kernel_thread+0x30/0x60
  [0000000000472fd0] kthreadd+0xf0/0x160
 ---[ end trace 429b268a213317ba ]---

This patch fixes generic percpu functions and sparc64
setup_per_cpu_areas() so that they handle sparse cpu_possible_map
properly.

Please note that on x86, cpu_possible_map() doesn't contain holes and
thus num_possible_cpus() == nr_cpu_ids and this patch doesn't cause
any behavior difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: David S. Miller <davem@davemloft.net>
Cc: Ingo Molnar <mingo@elte.hu>
---
The previously mentioned bug fixed.

 arch/sparc/kernel/smp_64.c     |    4 ++--
 arch/x86/kernel/setup_percpu.c |   14 +++++++-------
 mm/percpu.c                    |   33 ++++++++++++++++++---------------
 3 files changed, 27 insertions(+), 24 deletions(-)

diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c
index fa44eaf..3691907 100644
--- a/arch/sparc/kernel/smp_64.c
+++ b/arch/sparc/kernel/smp_64.c
@@ -1499,7 +1499,7 @@ void __init setup_per_cpu_areas(void)
 	dyn_size = pcpur_size - static_size - PERCPU_MODULE_RESERVE;
 
 
-	ptrs_size = PFN_ALIGN(num_possible_cpus() * sizeof(pcpur_ptrs[0]));
+	ptrs_size = PFN_ALIGN(nr_cpu_ids * sizeof(pcpur_ptrs[0]));
 	pcpur_ptrs = alloc_bootmem(ptrs_size);
 
 	for_each_possible_cpu(cpu) {
@@ -1514,7 +1514,7 @@ void __init setup_per_cpu_areas(void)
 
 	/* allocate address and map */
 	vm.flags = VM_ALLOC;
-	vm.size = num_possible_cpus() * PCPU_CHUNK_SIZE;
+	vm.size = nr_cpu_ids * PCPU_CHUNK_SIZE;
 	vm_area_register_early(&vm, PCPU_CHUNK_SIZE);
 
 	for_each_possible_cpu(cpu) {
diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c
index 29a3eef..07d8191 100644
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -165,7 +165,7 @@ static ssize_t __init setup_pcpu_lpage(size_t static_size, bool chosen)
 
 	if (!chosen) {
 		size_t vm_size = VMALLOC_END - VMALLOC_START;
-		size_t tot_size = num_possible_cpus() * PMD_SIZE;
+		size_t tot_size = nr_cpu_ids * PMD_SIZE;
 
 		/* on non-NUMA, embedding is better */
 		if (!pcpu_need_numa())
@@ -199,7 +199,7 @@ static ssize_t __init setup_pcpu_lpage(size_t static_size, bool chosen)
 	dyn_size = pcpul_size - static_size - PERCPU_FIRST_CHUNK_RESERVE;
 
 	/* allocate pointer array and alloc large pages */
-	map_size = PFN_ALIGN(num_possible_cpus() * sizeof(pcpul_map[0]));
+	map_size = PFN_ALIGN(nr_cpu_ids * sizeof(pcpul_map[0]));
 	pcpul_map = alloc_bootmem(map_size);
 
 	for_each_possible_cpu(cpu) {
@@ -228,7 +228,7 @@ static ssize_t __init setup_pcpu_lpage(size_t static_size, bool chosen)
 
 	/* allocate address and map */
 	pcpul_vm.flags = VM_ALLOC;
-	pcpul_vm.size = num_possible_cpus() * PMD_SIZE;
+	pcpul_vm.size = nr_cpu_ids * PMD_SIZE;
 	vm_area_register_early(&pcpul_vm, PMD_SIZE);
 
 	for_each_possible_cpu(cpu) {
@@ -250,8 +250,8 @@ static ssize_t __init setup_pcpu_lpage(size_t static_size, bool chosen)
 				     PMD_SIZE, pcpul_vm.addr, NULL);
 
 	/* sort pcpul_map array for pcpu_lpage_remapped() */
-	for (i = 0; i < num_possible_cpus() - 1; i++)
-		for (j = i + 1; j < num_possible_cpus(); j++)
+	for (i = 0; i < nr_cpu_ids - 1; i++)
+		for (j = i + 1; j < nr_cpu_ids; j++)
 			if (pcpul_map[i].ptr > pcpul_map[j].ptr) {
 				struct pcpul_ent tmp = pcpul_map[i];
 				pcpul_map[i] = pcpul_map[j];
@@ -288,7 +288,7 @@ void *pcpu_lpage_remapped(void *kaddr)
 {
 	void *pmd_addr = (void *)((unsigned long)kaddr & PMD_MASK);
 	unsigned long offset = (unsigned long)kaddr & ~PMD_MASK;
-	int left = 0, right = num_possible_cpus() - 1;
+	int left = 0, right = nr_cpu_ids - 1;
 	int pos;
 
 	/* pcpul in use at all? */
@@ -377,7 +377,7 @@ static ssize_t __init setup_pcpu_4k(size_t static_size)
 	pcpu4k_nr_static_pages = PFN_UP(static_size);
 
 	/* unaligned allocations can't be freed, round up to page size */
-	pages_size = PFN_ALIGN(pcpu4k_nr_static_pages * num_possible_cpus()
+	pages_size = PFN_ALIGN(pcpu4k_nr_static_pages * nr_cpu_ids
 			       * sizeof(pcpu4k_pages[0]));
 	pcpu4k_pages = alloc_bootmem(pages_size);
 
diff --git a/mm/percpu.c b/mm/percpu.c
index b70f2ac..e0be114 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -8,12 +8,12 @@
  *
  * This is percpu allocator which can handle both static and dynamic
  * areas.  Percpu areas are allocated in chunks in vmalloc area.  Each
- * chunk is consisted of num_possible_cpus() units and the first chunk
- * is used for static percpu variables in the kernel image (special
- * boot time alloc/init handling necessary as these areas need to be
- * brought up before allocation services are running).  Unit grows as
- * necessary and all units grow or shrink in unison.  When a chunk is
- * filled up, another chunk is allocated.  ie. in vmalloc area
+ * chunk is consisted of nr_cpu_ids units and the first chunk is used
+ * for static percpu variables in the kernel image (special boot time
+ * alloc/init handling necessary as these areas need to be brought up
+ * before allocation services are running).  Unit grows as necessary
+ * and all units grow or shrink in unison.  When a chunk is filled up,
+ * another chunk is allocated.  ie. in vmalloc area
  *
  *  c0                           c1                         c2
  *  -------------------          -------------------        ------------
@@ -558,7 +558,7 @@ static void pcpu_free_area(struct pcpu_chunk *chunk, int freeme)
 static void pcpu_unmap(struct pcpu_chunk *chunk, int page_start, int page_end,
 		       bool flush_tlb)
 {
-	unsigned int last = num_possible_cpus() - 1;
+	unsigned int last = nr_cpu_ids - 1;
 	unsigned int cpu;
 
 	/* unmap must not be done on immutable chunk */
@@ -643,7 +643,7 @@ static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk, int off, int size,
  */
 static int pcpu_map(struct pcpu_chunk *chunk, int page_start, int page_end)
 {
-	unsigned int last = num_possible_cpus() - 1;
+	unsigned int last = nr_cpu_ids - 1;
 	unsigned int cpu;
 	int err;
 
@@ -1067,9 +1067,9 @@ size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
 					PFN_UP(size_sum));
 
 	pcpu_unit_size = pcpu_unit_pages << PAGE_SHIFT;
-	pcpu_chunk_size = num_possible_cpus() * pcpu_unit_size;
+	pcpu_chunk_size = nr_cpu_ids * pcpu_unit_size;
 	pcpu_chunk_struct_size = sizeof(struct pcpu_chunk)
-		+ num_possible_cpus() * pcpu_unit_pages * sizeof(struct page *);
+		+ nr_cpu_ids * pcpu_unit_pages * sizeof(struct page *);
 
 	if (dyn_size < 0)
 		dyn_size = pcpu_unit_size - static_size - reserved_size;
@@ -1248,7 +1248,7 @@ ssize_t __init pcpu_embed_first_chunk(size_t static_size, size_t reserved_size,
 	} else
 		pcpue_unit_size = max_t(size_t, pcpue_size, PCPU_MIN_UNIT_SIZE);
 
-	chunk_size = pcpue_unit_size * num_possible_cpus();
+	chunk_size = pcpue_unit_size * nr_cpu_ids;
 
 	pcpue_ptr = __alloc_bootmem_nopanic(chunk_size, PAGE_SIZE,
 					    __pa(MAX_DMA_ADDRESS));
@@ -1259,12 +1259,15 @@ ssize_t __init pcpu_embed_first_chunk(size_t static_size, size_t reserved_size,
 	}
 
 	/* return the leftover and copy */
-	for_each_possible_cpu(cpu) {
+	for (cpu = 0; cpu < nr_cpu_ids; cpu++) {
 		void *ptr = pcpue_ptr + cpu * pcpue_unit_size;
 
-		free_bootmem(__pa(ptr + pcpue_size),
-			     pcpue_unit_size - pcpue_size);
-		memcpy(ptr, __per_cpu_load, static_size);
+		if (cpu_possible(cpu)) {
+			free_bootmem(__pa(ptr + pcpue_size),
+				     pcpue_unit_size - pcpue_size);
+			memcpy(ptr, __per_cpu_load, static_size);
+		} else
+			free_bootmem(__pa(ptr), pcpue_unit_size);
 	}
 
 	/* we're ready, commit */
-- 
1.6.0.2