[GIT PATCH core/percpu] x86,percpu: fix pageattr handling with remap allocator, take#4

[GIT PATCH core/percpu] x86,percpu: fix pageattr handling with remap allocator, take#4

[Tejun Heo]

Hello,

Upon ack, please pull from the following git tree.

  git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc.git tj-percpu-fix-remap

This is the third take of x86-percpu-fix-pageattr patchset.  Changes
from the last take[L] are...

* Rebased on top of linus#master + tj-percpu-convert-most-archs, take#3

* Dup free in setup_pcpu_remap() fixed.

* remap allocator renamed to lpage.

* Changes to cpa_process_alias() updated such that the remap handling
  code doesn't consider multipage case and trigger WARN_ON() if @cpa
  at that point has numpages higher than 1.  Because the target PMD
  page is always partially recycled, it always ends up splitted to 4k
  pages and thus numpages is guaranteed to be 1 at that point.

This patchset contains the following seven patches.

 0001-x86-fix-duplicate-free-in-setup_pcpu_remap-failur.patch
 0002-x86-rename-remap-percpu-first-chunk-allocator-to-lp.patch
 0003-x86-prepare-setup_pcpu_lpage-for-pageattr-fix.patch
 0004-x86-reorganize-cpa_process_alias.patch
 0005-x86-fix-pageattr-handling-for-lpage-percpu-allocato.patch
 0006-x86-implement-percpu_alloc-kernel-parameter.patch
 0007-x86-ensure-percpu-lpage-doesn-t-consume-too-much-vm.patch

0001 and 0002 are new ones.  0005 has the cpa_process_alias() change
updated describd above.  Other than that, no notable changes.

This patchset is on top of

linus-2.6#master (300df7dc89cc276377fc020704e34875d5c473b6)
+ [1] tj-percpu-convert-most-archs, take#3

and contains the following changes.

 Documentation/kernel-parameters.txt |    6 
 arch/x86/include/asm/percpu.h       |    9 +
 arch/x86/kernel/setup_percpu.c      |  219 ++++++++++++++++++++++++++----------
 arch/x86/mm/pageattr.c              |   65 ++++++----
 mm/percpu.c                         |   13 +-
 5 files changed, 226 insertions(+), 86 deletions(-)

Thanks.

--
tejun

[L] http://thread.gmane.org/gmane.linux.kernel/844298
[1] http://thread.gmane.org/gmane.linux.kernel.cross-arch/3818

[PATCH 1/7] x86: fix duplicate free in setup_pcpu_remap() failure path

[Tejun Heo]

In the failure path, setup_pcpu_remap() tries to free the area which
has already been freed to make holes in the large page.  Fix it.

[ Impact: fix duplicate free in failure path ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
---
 arch/x86/kernel/setup_percpu.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c
index 9c3f082..dfbc7e6 100644
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -228,7 +228,7 @@ static ssize_t __init setup_pcpu_remap(size_t static_size)
 enomem:
 	for_each_possible_cpu(cpu)
 		if (pcpur_ptrs[cpu])
-			free_bootmem(__pa(pcpur_ptrs[cpu]), PMD_SIZE);
+			free_bootmem(__pa(pcpur_ptrs[cpu]), pcpur_size);
 	ret = -ENOMEM;
 out_free_ar:
 	free_bootmem(__pa(pcpur_ptrs), ptrs_size);
-- 
1.6.0.2

[PATCH 2/7] x86: rename remap percpu first chunk allocator to lpage

[Tejun Heo]

The "remap" allocator remaps large pages to build the first chunk;
however, the name isn't very good because 4k allocator remaps too and
the whole point of the remap allocator is using large page mapping.
The allocator will be generalized and exported outside of x86, rename
it to lpage before that happens.

percpu_alloc kernel parameter is updated to accept both "remap" and
"lpage" for lpage allocator.

[ Impact: code cleanup, kernel parameter argument updated ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
---
 arch/x86/kernel/setup_percpu.c |   50 ++++++++++++++++++++--------------------
 1 files changed, 25 insertions(+), 25 deletions(-)

diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c
index dfbc7e6..8794c0c 100644
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -124,7 +124,7 @@ static void * __init pcpu_alloc_bootmem(unsigned int cpu, unsigned long size,
 }
 
 /*
- * Remap allocator
+ * Large page remap allocator
  *
  * This allocator uses PMD page as unit.  A PMD page is allocated for
  * each cpu and each is remapped into vmalloc area using PMD mapping.
@@ -137,20 +137,20 @@ static void * __init pcpu_alloc_bootmem(unsigned int cpu, unsigned long size,
  * better than only using 4k mappings while still being NUMA friendly.
  */
 #ifdef CONFIG_NEED_MULTIPLE_NODES
-static size_t pcpur_size __initdata;
-static void **pcpur_ptrs __initdata;
+static size_t pcpul_size __initdata;
+static void **pcpul_ptrs __initdata;
 
-static struct page * __init pcpur_get_page(unsigned int cpu, int pageno)
+static struct page * __init pcpul_get_page(unsigned int cpu, int pageno)
 {
 	size_t off = (size_t)pageno << PAGE_SHIFT;
 
-	if (off >= pcpur_size)
+	if (off >= pcpul_size)
 		return NULL;
 
-	return virt_to_page(pcpur_ptrs[cpu] + off);
+	return virt_to_page(pcpul_ptrs[cpu] + off);
 }
 
-static ssize_t __init setup_pcpu_remap(size_t static_size)
+static ssize_t __init setup_pcpu_lpage(size_t static_size)
 {
 	static struct vm_struct vm;
 	size_t ptrs_size, dyn_size;
@@ -170,36 +170,36 @@ static ssize_t __init setup_pcpu_remap(size_t static_size)
 	 * Currently supports only single page.  Supporting multiple
 	 * pages won't be too difficult if it ever becomes necessary.
 	 */
-	pcpur_size = PFN_ALIGN(static_size + PERCPU_MODULE_RESERVE +
+	pcpul_size = PFN_ALIGN(static_size + PERCPU_MODULE_RESERVE +
 			       PERCPU_DYNAMIC_RESERVE);
-	if (pcpur_size > PMD_SIZE) {
+	if (pcpul_size > PMD_SIZE) {
 		pr_warning("PERCPU: static data is larger than large page, "
 			   "can't use large page\n");
 		return -EINVAL;
 	}
-	dyn_size = pcpur_size - static_size - PERCPU_FIRST_CHUNK_RESERVE;
+	dyn_size = pcpul_size - static_size - PERCPU_FIRST_CHUNK_RESERVE;
 
 	/* allocate pointer array and alloc large pages */
-	ptrs_size = PFN_ALIGN(num_possible_cpus() * sizeof(pcpur_ptrs[0]));
-	pcpur_ptrs = alloc_bootmem(ptrs_size);
+	ptrs_size = PFN_ALIGN(num_possible_cpus() * sizeof(pcpul_ptrs[0]));
+	pcpul_ptrs = alloc_bootmem(ptrs_size);
 
 	for_each_possible_cpu(cpu) {
-		pcpur_ptrs[cpu] = pcpu_alloc_bootmem(cpu, PMD_SIZE, PMD_SIZE);
-		if (!pcpur_ptrs[cpu])
+		pcpul_ptrs[cpu] = pcpu_alloc_bootmem(cpu, PMD_SIZE, PMD_SIZE);
+		if (!pcpul_ptrs[cpu])
 			goto enomem;
 
 		/*
-		 * Only use pcpur_size bytes and give back the rest.
+		 * Only use pcpul_size bytes and give back the rest.
 		 *
 		 * Ingo: The 2MB up-rounding bootmem is needed to make
 		 * sure the partial 2MB page is still fully RAM - it's
 		 * not well-specified to have a PAT-incompatible area
 		 * (unmapped RAM, device memory, etc.) in that hole.
 		 */
-		free_bootmem(__pa(pcpur_ptrs[cpu] + pcpur_size),
-			     PMD_SIZE - pcpur_size);
+		free_bootmem(__pa(pcpul_ptrs[cpu] + pcpul_size),
+			     PMD_SIZE - pcpul_size);
 
-		memcpy(pcpur_ptrs[cpu], __per_cpu_load, static_size);
+		memcpy(pcpul_ptrs[cpu], __per_cpu_load, static_size);
 	}
 
 	/* allocate address and map */
@@ -212,7 +212,7 @@ static ssize_t __init setup_pcpu_remap(size_t static_size)
 
 		pmd = populate_extra_pmd((unsigned long)vm.addr
 					 + cpu * PMD_SIZE);
-		set_pmd(pmd, pfn_pmd(page_to_pfn(virt_to_page(pcpur_ptrs[cpu])),
+		set_pmd(pmd, pfn_pmd(page_to_pfn(virt_to_page(pcpul_ptrs[cpu])),
 				     PAGE_KERNEL_LARGE));
 	}
 
@@ -220,22 +220,22 @@ static ssize_t __init setup_pcpu_remap(size_t static_size)
 	pr_info("PERCPU: Remapped at %p with large pages, static data "
 		"%zu bytes\n", vm.addr, static_size);
 
-	ret = pcpu_setup_first_chunk(pcpur_get_page, static_size,
+	ret = pcpu_setup_first_chunk(pcpul_get_page, static_size,
 				     PERCPU_FIRST_CHUNK_RESERVE, dyn_size,
 				     PMD_SIZE, vm.addr, NULL);
 	goto out_free_ar;
 
 enomem:
 	for_each_possible_cpu(cpu)
-		if (pcpur_ptrs[cpu])
-			free_bootmem(__pa(pcpur_ptrs[cpu]), pcpur_size);
+		if (pcpul_ptrs[cpu])
+			free_bootmem(__pa(pcpul_ptrs[cpu]), pcpul_size);
 	ret = -ENOMEM;
 out_free_ar:
-	free_bootmem(__pa(pcpur_ptrs), ptrs_size);
+	free_bootmem(__pa(pcpul_ptrs), ptrs_size);
 	return ret;
 }
 #else
-static ssize_t __init setup_pcpu_remap(size_t static_size)
+static ssize_t __init setup_pcpu_lpage(size_t static_size)
 {
 	return -EINVAL;
 }
@@ -367,7 +367,7 @@ void __init setup_per_cpu_areas(void)
 	 * of large page mappings.  Please read comments on top of
 	 * each allocator for details.
 	 */
-	ret = setup_pcpu_remap(static_size);
+	ret = setup_pcpu_lpage(static_size);
 	if (ret < 0)
 		ret = setup_pcpu_embed(static_size);
 	if (ret < 0)
-- 
1.6.0.2

[PATCH 3/7] x86: prepare setup_pcpu_lpage() for pageattr fix

[Tejun Heo]

Make the following changes in preparation of coming pageattr updates.

* Define and use array of struct pcpul_ent instead of array of
  pointers.  The only difference is ->cpu field which is set but
  unused yet.

* Rename variables according to the above change.

* Rename local variable vm to pcpul_vm and move it out of the
  function.

[ Impact: no functional difference ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jan Beulich <JBeulich@novell.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Ingo Molnar <mingo@elte.hu>
---
 arch/x86/kernel/setup_percpu.c |   58 ++++++++++++++++++++++-----------------
 1 files changed, 33 insertions(+), 25 deletions(-)

diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c
index 8794c0c..7d38941 100644
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -137,8 +137,14 @@ static void * __init pcpu_alloc_bootmem(unsigned int cpu, unsigned long size,
  * better than only using 4k mappings while still being NUMA friendly.
  */
 #ifdef CONFIG_NEED_MULTIPLE_NODES
+struct pcpul_ent {
+	unsigned int	cpu;
+	void		*ptr;
+};
+
 static size_t pcpul_size __initdata;
-static void **pcpul_ptrs __initdata;
+static struct pcpul_ent *pcpul_map __initdata;
+static struct vm_struct pcpul_vm;
 
 static struct page * __init pcpul_get_page(unsigned int cpu, int pageno)
 {
@@ -147,13 +153,12 @@ static struct page * __init pcpul_get_page(unsigned int cpu, int pageno)
 	if (off >= pcpul_size)
 		return NULL;
 
-	return virt_to_page(pcpul_ptrs[cpu] + off);
+	return virt_to_page(pcpul_map[cpu].ptr + off);
 }
 
 static ssize_t __init setup_pcpu_lpage(size_t static_size)
 {
-	static struct vm_struct vm;
-	size_t ptrs_size, dyn_size;
+	size_t map_size, dyn_size;
 	unsigned int cpu;
 	ssize_t ret;
 
@@ -180,12 +185,14 @@ static ssize_t __init setup_pcpu_lpage(size_t static_size)
 	dyn_size = pcpul_size - static_size - PERCPU_FIRST_CHUNK_RESERVE;
 
 	/* allocate pointer array and alloc large pages */
-	ptrs_size = PFN_ALIGN(num_possible_cpus() * sizeof(pcpul_ptrs[0]));
-	pcpul_ptrs = alloc_bootmem(ptrs_size);
+	map_size = PFN_ALIGN(num_possible_cpus() * sizeof(pcpul_map[0]));
+	pcpul_map = alloc_bootmem(map_size);
 
 	for_each_possible_cpu(cpu) {
-		pcpul_ptrs[cpu] = pcpu_alloc_bootmem(cpu, PMD_SIZE, PMD_SIZE);
-		if (!pcpul_ptrs[cpu])
+		pcpul_map[cpu].cpu = cpu;
+		pcpul_map[cpu].ptr = pcpu_alloc_bootmem(cpu, PMD_SIZE,
+							PMD_SIZE);
+		if (!pcpul_map[cpu].ptr)
 			goto enomem;
 
 		/*
@@ -196,42 +203,43 @@ static ssize_t __init setup_pcpu_lpage(size_t static_size)
 		 * not well-specified to have a PAT-incompatible area
 		 * (unmapped RAM, device memory, etc.) in that hole.
 		 */
-		free_bootmem(__pa(pcpul_ptrs[cpu] + pcpul_size),
+		free_bootmem(__pa(pcpul_map[cpu].ptr + pcpul_size),
 			     PMD_SIZE - pcpul_size);
 
-		memcpy(pcpul_ptrs[cpu], __per_cpu_load, static_size);
+		memcpy(pcpul_map[cpu].ptr, __per_cpu_load, static_size);
 	}
 
 	/* allocate address and map */
-	vm.flags = VM_ALLOC;
-	vm.size = num_possible_cpus() * PMD_SIZE;
-	vm_area_register_early(&vm, PMD_SIZE);
+	pcpul_vm.flags = VM_ALLOC;
+	pcpul_vm.size = num_possible_cpus() * PMD_SIZE;
+	vm_area_register_early(&pcpul_vm, PMD_SIZE);
 
 	for_each_possible_cpu(cpu) {
-		pmd_t *pmd;
+		pmd_t *pmd, pmd_v;
 
-		pmd = populate_extra_pmd((unsigned long)vm.addr
-					 + cpu * PMD_SIZE);
-		set_pmd(pmd, pfn_pmd(page_to_pfn(virt_to_page(pcpul_ptrs[cpu])),
-				     PAGE_KERNEL_LARGE));
+		pmd = populate_extra_pmd((unsigned long)pcpul_vm.addr +
+					 cpu * PMD_SIZE);
+		pmd_v = pfn_pmd(page_to_pfn(virt_to_page(pcpul_map[cpu].ptr)),
+				PAGE_KERNEL_LARGE);
+		set_pmd(pmd, pmd_v);
 	}
 
 	/* we're ready, commit */
 	pr_info("PERCPU: Remapped at %p with large pages, static data "
-		"%zu bytes\n", vm.addr, static_size);
+		"%zu bytes\n", pcpul_vm.addr, static_size);
 
 	ret = pcpu_setup_first_chunk(pcpul_get_page, static_size,
 				     PERCPU_FIRST_CHUNK_RESERVE, dyn_size,
-				     PMD_SIZE, vm.addr, NULL);
-	goto out_free_ar;
+				     PMD_SIZE, pcpul_vm.addr, NULL);
+	goto out_free_map;
 
 enomem:
 	for_each_possible_cpu(cpu)
-		if (pcpul_ptrs[cpu])
-			free_bootmem(__pa(pcpul_ptrs[cpu]), pcpul_size);
+		if (pcpul_map[cpu].ptr)
+			free_bootmem(__pa(pcpul_map[cpu].ptr), pcpul_size);
 	ret = -ENOMEM;
-out_free_ar:
-	free_bootmem(__pa(pcpul_ptrs), ptrs_size);
+out_free_map:
+	free_bootmem(__pa(pcpul_map), map_size);
 	return ret;
 }
 #else
-- 
1.6.0.2

[PATCH 4/7] x86: reorganize cpa_process_alias()

[Tejun Heo]

Reorganize cpa_process_alias() so that new alias condition can be
added easily.

Jan Beulich spotted problem in the original cleanup thread which
incorrectly assumed the two existing conditions were mutially
exclusive.

[ Impact: code reorganization ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jan Beulich <JBeulich@novell.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Ingo Molnar <mingo@elte.hu>
---
 arch/x86/mm/pageattr.c |   50 ++++++++++++++++++++++-------------------------
 1 files changed, 23 insertions(+), 27 deletions(-)

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 6ce9518..911b1f1 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -681,8 +681,9 @@ static int __change_page_attr_set_clr(struct cpa_data *cpa, int checkalias);
 static int cpa_process_alias(struct cpa_data *cpa)
 {
 	struct cpa_data alias_cpa;
-	int ret = 0;
-	unsigned long temp_cpa_vaddr, vaddr;
+	unsigned long laddr = (unsigned long)__va(cpa->pfn << PAGE_SHIFT);
+	unsigned long vaddr;
+	int ret;
 
 	if (cpa->pfn >= max_pfn_mapped)
 		return 0;
@@ -706,42 +707,37 @@ static int cpa_process_alias(struct cpa_data *cpa)
 		    PAGE_OFFSET + (max_pfn_mapped << PAGE_SHIFT)))) {
 
 		alias_cpa = *cpa;
-		temp_cpa_vaddr = (unsigned long) __va(cpa->pfn << PAGE_SHIFT);
-		alias_cpa.vaddr = &temp_cpa_vaddr;
+		alias_cpa.vaddr = &laddr;
 		alias_cpa.flags &= ~(CPA_PAGES_ARRAY | CPA_ARRAY);
 
-
 		ret = __change_page_attr_set_clr(&alias_cpa, 0);
+		if (ret)
+			return ret;
 	}
 
 #ifdef CONFIG_X86_64
-	if (ret)
-		return ret;
 	/*
-	 * No need to redo, when the primary call touched the high
-	 * mapping already:
-	 */
-	if (within(vaddr, (unsigned long) _text, _brk_end))
-		return 0;
-
-	/*
-	 * If the physical address is inside the kernel map, we need
+	 * If the primary call didn't touch the high mapping already
+	 * and the physical address is inside the kernel map, we need
 	 * to touch the high mapped kernel as well:
 	 */
-	if (!within(cpa->pfn, highmap_start_pfn(), highmap_end_pfn()))
-		return 0;
-
-	alias_cpa = *cpa;
-	temp_cpa_vaddr = (cpa->pfn << PAGE_SHIFT) + __START_KERNEL_map - phys_base;
-	alias_cpa.vaddr = &temp_cpa_vaddr;
-	alias_cpa.flags &= ~(CPA_PAGES_ARRAY | CPA_ARRAY);
+	if (!within(vaddr, (unsigned long)_text, _brk_end) &&
+	    within(cpa->pfn, highmap_start_pfn(), highmap_end_pfn())) {
+		unsigned long temp_cpa_vaddr = (cpa->pfn << PAGE_SHIFT) +
+					       __START_KERNEL_map - phys_base;
+		alias_cpa = *cpa;
+		alias_cpa.vaddr = &temp_cpa_vaddr;
+		alias_cpa.flags &= ~(CPA_PAGES_ARRAY | CPA_ARRAY);
 
-	/*
-	 * The high mapping range is imprecise, so ignore the return value.
-	 */
-	__change_page_attr_set_clr(&alias_cpa, 0);
+		/*
+		 * The high mapping range is imprecise, so ignore the
+		 * return value.
+		 */
+		__change_page_attr_set_clr(&alias_cpa, 0);
+	}
 #endif
-	return ret;
+
+	return 0;
 }
 
 static int __change_page_attr_set_clr(struct cpa_data *cpa, int checkalias)
-- 
1.6.0.2

[PATCH 5/7] x86: fix pageattr handling for lpage percpu allocator and re-enable it

[Tejun Heo]

lpage allocator aliases a PMD page for each cpu and returns whatever
is unused to the page allocator.  When the pageattr of the recycled
pages are changed, this makes the two aliases point to the overlapping
regions with different attributes which isn't allowed and known to
cause subtle data corruption in certain cases.

This can be handled in simliar manner to the x86_64 highmap alias.
pageattr code should detect if the target pages have PMD alias and
split the PMD alias and synchronize the attributes.

pcpur allocator is updated to keep the allocated PMD pages map sorted
in ascending address order and provide pcpu_lpage_remapped() function
which binary searches the array to determine whether the given address
is aliased and if so to which address.  pageattr is updated to use
pcpu_lpage_remapped() to detect the PMD alias and split it up as
necessary from cpa_process_alias().

Jan Beulich spotted the original problem and incorrect usage of vaddr
instead of laddr for lookup.

With this, lpage percpu allocator should work correctly.  Re-enable
it.

[ Impact: fix subtle lpage pageattr bug and re-enable lpage ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Jan Beulich <JBeulich@novell.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Ingo Molnar <mingo@elte.hu>
---
 arch/x86/include/asm/percpu.h  |    9 +++++
 arch/x86/kernel/setup_percpu.c |   72 +++++++++++++++++++++++++++++++++++-----
 arch/x86/mm/pageattr.c         |   21 +++++++++++-
 3 files changed, 92 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index 02ecb30..7e4111f 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -155,6 +155,15 @@ do {							\
 /* We can use this directly for local CPU (faster). */
 DECLARE_PER_CPU(unsigned long, this_cpu_off);
 
+#ifdef CONFIG_NEED_MULTIPLE_NODES
+void *pcpu_lpage_remapped(void *kaddr);
+#else
+static inline void *pcpu_lpage_remapped(void *kaddr)
+{
+	return NULL;
+}
+#endif
+
 #endif /* !__ASSEMBLY__ */
 
 #ifdef CONFIG_SMP
diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c
index 7d38941..bad2fd2 100644
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -142,8 +142,8 @@ struct pcpul_ent {
 	void		*ptr;
 };
 
-static size_t pcpul_size __initdata;
-static struct pcpul_ent *pcpul_map __initdata;
+static size_t pcpul_size;
+static struct pcpul_ent *pcpul_map;
 static struct vm_struct pcpul_vm;
 
 static struct page * __init pcpul_get_page(unsigned int cpu, int pageno)
@@ -160,15 +160,14 @@ static ssize_t __init setup_pcpu_lpage(size_t static_size)
 {
 	size_t map_size, dyn_size;
 	unsigned int cpu;
+	int i, j;
 	ssize_t ret;
 
 	/*
 	 * If large page isn't supported, there's no benefit in doing
 	 * this.  Also, on non-NUMA, embedding is better.
-	 *
-	 * NOTE: disabled for now.
 	 */
-	if (true || !cpu_has_pse || !pcpu_need_numa())
+	if (!cpu_has_pse || !pcpu_need_numa())
 		return -EINVAL;
 
 	/*
@@ -231,16 +230,71 @@ static ssize_t __init setup_pcpu_lpage(size_t static_size)
 	ret = pcpu_setup_first_chunk(pcpul_get_page, static_size,
 				     PERCPU_FIRST_CHUNK_RESERVE, dyn_size,
 				     PMD_SIZE, pcpul_vm.addr, NULL);
-	goto out_free_map;
+
+	/* 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++)
+			if (pcpul_map[i].ptr > pcpul_map[j].ptr) {
+				struct pcpul_ent tmp = pcpul_map[i];
+				pcpul_map[i] = pcpul_map[j];
+				pcpul_map[j] = tmp;
+			}
+
+	return ret;
 
 enomem:
 	for_each_possible_cpu(cpu)
 		if (pcpul_map[cpu].ptr)
 			free_bootmem(__pa(pcpul_map[cpu].ptr), pcpul_size);
-	ret = -ENOMEM;
-out_free_map:
 	free_bootmem(__pa(pcpul_map), map_size);
-	return ret;
+	return -ENOMEM;
+}
+
+/**
+ * pcpu_lpage_remapped - determine whether a kaddr is in pcpul recycled area
+ * @kaddr: the kernel address in question
+ *
+ * Determine whether @kaddr falls in the pcpul recycled area.  This is
+ * used by pageattr to detect VM aliases and break up the pcpu PMD
+ * mapping such that the same physical page is not mapped under
+ * different attributes.
+ *
+ * The recycled area is always at the tail of a partially used PMD
+ * page.
+ *
+ * RETURNS:
+ * Address of corresponding remapped pcpu address if match is found;
+ * otherwise, NULL.
+ */
+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 pos;
+
+	/* pcpul in use at all? */
+	if (!pcpul_map)
+		return NULL;
+
+	/* okay, perform binary search */
+	while (left <= right) {
+		pos = (left + right) / 2;
+
+		if (pcpul_map[pos].ptr < pmd_addr)
+			left = pos + 1;
+		else if (pcpul_map[pos].ptr > pmd_addr)
+			right = pos - 1;
+		else {
+			/* it shouldn't be in the area for the first chunk */
+			WARN_ON(offset < pcpul_size);
+
+			return pcpul_vm.addr +
+				pcpul_map[pos].cpu * PMD_SIZE + offset;
+		}
+	}
+
+	return NULL;
 }
 #else
 static ssize_t __init setup_pcpu_lpage(size_t static_size)
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 911b1f1..9f9b8c2 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -11,6 +11,7 @@
 #include <linux/interrupt.h>
 #include <linux/seq_file.h>
 #include <linux/debugfs.h>
+#include <linux/pfn.h>
 
 #include <asm/e820.h>
 #include <asm/processor.h>
@@ -682,7 +683,7 @@ static int cpa_process_alias(struct cpa_data *cpa)
 {
 	struct cpa_data alias_cpa;
 	unsigned long laddr = (unsigned long)__va(cpa->pfn << PAGE_SHIFT);
-	unsigned long vaddr;
+	unsigned long vaddr, remapped;
 	int ret;
 
 	if (cpa->pfn >= max_pfn_mapped)
@@ -737,6 +738,24 @@ static int cpa_process_alias(struct cpa_data *cpa)
 	}
 #endif
 
+	/*
+	 * If the PMD page was partially used for per-cpu remapping,
+	 * the recycled area needs to be split and modified.  Because
+	 * the area is always proper subset of a PMD page
+	 * cpa->numpages is guaranteed to be 1 for these areas, so
+	 * there's no need to loop over and check for further remaps.
+	 */
+	remapped = (unsigned long)pcpu_lpage_remapped((void *)laddr);
+	if (remapped) {
+		WARN_ON(cpa->numpages > 1);
+		alias_cpa = *cpa;
+		alias_cpa.vaddr = &remapped;
+		alias_cpa.flags &= ~(CPA_PAGES_ARRAY | CPA_ARRAY);
+		ret = __change_page_attr_set_clr(&alias_cpa, 0);
+		if (ret)
+			return ret;
+	}
+
 	return 0;
 }
 
-- 
1.6.0.2

[PATCH 6/7] x86: implement percpu_alloc kernel parameter

[Tejun Heo]

According to Andi, it isn't clear whether lpage allocator is worth the
trouble as there are many processors where PMD TLB is far scarcer than
PTE TLB.  The advantage or disadvantage probably depends on the actual
size of percpu area and specific processor.  As performance
degradation due to TLB pressure tends to be highly workload specific
and subtle, it is difficult to decide which way to go without more
data.

This patch implements percpu_alloc kernel parameter to allow selecting
which first chunk allocator to use to ease debugging and testing.

While at it, make sure all the failure paths report why something
failed to help determining why certain allocator isn't working.  Also,
kill the "Great future plan" comment which had already been realized
quite some time ago.

[ Impact: allow explicit percpu first chunk allocator selection ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Jan Beulich <JBeulich@novell.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Ingo Molnar <mingo@elte.hu>
---
 Documentation/kernel-parameters.txt |    6 +++
 arch/x86/kernel/setup_percpu.c      |   69 +++++++++++++++++++++++++----------
 mm/percpu.c                         |   13 +++++--
 3 files changed, 65 insertions(+), 23 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index ad38006..6115149 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1871,6 +1871,12 @@ and is between 256 and 4096 characters. It is defined in the file
 			Format: { 0 | 1 }
 			See arch/parisc/kernel/pdc_chassis.c
 
+	percpu_alloc=	[X86] Select which percpu first chunk allocator to use.
+			Allowed values are one of "lpage", "embed" and "4k".
+			See comments in arch/x86/kernel/setup_percpu.c for
+			details on each allocator.  This parameter is primarily
+			for debugging and performance comparison.
+
 	pf.		[PARIDE]
 			See Documentation/blockdev/paride.txt.
 
diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c
index bad2fd2..165ebd5 100644
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -156,20 +156,23 @@ static struct page * __init pcpul_get_page(unsigned int cpu, int pageno)
 	return virt_to_page(pcpul_map[cpu].ptr + off);
 }
 
-static ssize_t __init setup_pcpu_lpage(size_t static_size)
+static ssize_t __init setup_pcpu_lpage(size_t static_size, bool chosen)
 {
 	size_t map_size, dyn_size;
 	unsigned int cpu;
 	int i, j;
 	ssize_t ret;
 
-	/*
-	 * If large page isn't supported, there's no benefit in doing
-	 * this.  Also, on non-NUMA, embedding is better.
-	 */
-	if (!cpu_has_pse || !pcpu_need_numa())
+	/* on non-NUMA, embedding is better */
+	if (!chosen && !pcpu_need_numa())
 		return -EINVAL;
 
+	/* need PSE */
+	if (!cpu_has_pse) {
+		pr_warning("PERCPU: lpage allocator requires PSE\n");
+		return -EINVAL;
+	}
+
 	/*
 	 * Currently supports only single page.  Supporting multiple
 	 * pages won't be too difficult if it ever becomes necessary.
@@ -191,8 +194,11 @@ static ssize_t __init setup_pcpu_lpage(size_t static_size)
 		pcpul_map[cpu].cpu = cpu;
 		pcpul_map[cpu].ptr = pcpu_alloc_bootmem(cpu, PMD_SIZE,
 							PMD_SIZE);
-		if (!pcpul_map[cpu].ptr)
+		if (!pcpul_map[cpu].ptr) {
+			pr_warning("PERCPU: failed to allocate large page "
+				   "for cpu%u\n", cpu);
 			goto enomem;
+		}
 
 		/*
 		 * Only use pcpul_size bytes and give back the rest.
@@ -297,7 +303,7 @@ void *pcpu_lpage_remapped(void *kaddr)
 	return NULL;
 }
 #else
-static ssize_t __init setup_pcpu_lpage(size_t static_size)
+static ssize_t __init setup_pcpu_lpage(size_t static_size, bool chosen)
 {
 	return -EINVAL;
 }
@@ -311,7 +317,7 @@ static ssize_t __init setup_pcpu_lpage(size_t static_size)
  * mapping so that it can use PMD mapping without additional TLB
  * pressure.
  */
-static ssize_t __init setup_pcpu_embed(size_t static_size)
+static ssize_t __init setup_pcpu_embed(size_t static_size, bool chosen)
 {
 	size_t reserve = PERCPU_MODULE_RESERVE + PERCPU_DYNAMIC_RESERVE;
 
@@ -320,7 +326,7 @@ static ssize_t __init setup_pcpu_embed(size_t static_size)
 	 * this.  Also, embedding allocation doesn't play well with
 	 * NUMA.
 	 */
-	if (!cpu_has_pse || pcpu_need_numa())
+	if (!chosen && (!cpu_has_pse || pcpu_need_numa()))
 		return -EINVAL;
 
 	return pcpu_embed_first_chunk(static_size, PERCPU_FIRST_CHUNK_RESERVE,
@@ -370,8 +376,11 @@ static ssize_t __init setup_pcpu_4k(size_t static_size)
 			void *ptr;
 
 			ptr = pcpu_alloc_bootmem(cpu, PAGE_SIZE, PAGE_SIZE);
-			if (!ptr)
+			if (!ptr) {
+				pr_warning("PERCPU: failed to allocate "
+					   "4k page for cpu%u\n", cpu);
 				goto enomem;
+			}
 
 			memcpy(ptr, __per_cpu_load + i * PAGE_SIZE, PAGE_SIZE);
 			pcpu4k_pages[j++] = virt_to_page(ptr);
@@ -395,6 +404,16 @@ out_free_ar:
 	return ret;
 }
 
+/* for explicit first chunk allocator selection */
+static char pcpu_chosen_alloc[16] __initdata;
+
+static int __init percpu_alloc_setup(char *str)
+{
+	strncpy(pcpu_chosen_alloc, str, sizeof(pcpu_chosen_alloc) - 1);
+	return 0;
+}
+early_param("percpu_alloc", percpu_alloc_setup);
+
 static inline void setup_percpu_segment(int cpu)
 {
 #ifdef CONFIG_X86_32
@@ -408,11 +427,6 @@ static inline void setup_percpu_segment(int cpu)
 #endif
 }
 
-/*
- * Great future plan:
- * Declare PDA itself and support (irqstack,tss,pgd) as per cpu data.
- * Always point %gs to its beginning
- */
 void __init setup_per_cpu_areas(void)
 {
 	size_t static_size = __per_cpu_end - __per_cpu_start;
@@ -429,9 +443,26 @@ void __init setup_per_cpu_areas(void)
 	 * of large page mappings.  Please read comments on top of
 	 * each allocator for details.
 	 */
-	ret = setup_pcpu_lpage(static_size);
-	if (ret < 0)
-		ret = setup_pcpu_embed(static_size);
+	ret = -EINVAL;
+	if (strlen(pcpu_chosen_alloc)) {
+		if (strcmp(pcpu_chosen_alloc, "4k")) {
+			if (!strcmp(pcpu_chosen_alloc, "lpage"))
+				ret = setup_pcpu_lpage(static_size, true);
+			else if (!strcmp(pcpu_chosen_alloc, "embed"))
+				ret = setup_pcpu_embed(static_size, true);
+			else
+				pr_warning("PERCPU: unknown allocator %s "
+					   "specified\n", pcpu_chosen_alloc);
+			if (ret < 0)
+				pr_warning("PERCPU: %s allocator failed (%zd), "
+					   "falling back to 4k\n",
+					   pcpu_chosen_alloc, ret);
+		}
+	} else {
+		ret = setup_pcpu_lpage(static_size, false);
+		if (ret < 0)
+			ret = setup_pcpu_embed(static_size, false);
+	}
 	if (ret < 0)
 		ret = setup_pcpu_4k(static_size);
 	if (ret < 0)
diff --git a/mm/percpu.c b/mm/percpu.c
index 01a6fd9..b149845 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1233,6 +1233,7 @@ static struct page * __init pcpue_get_page(unsigned int cpu, int pageno)
 ssize_t __init pcpu_embed_first_chunk(size_t static_size, size_t reserved_size,
 				      ssize_t dyn_size, ssize_t unit_size)
 {
+	size_t chunk_size;
 	unsigned int cpu;
 
 	/* determine parameters and allocate */
@@ -1247,11 +1248,15 @@ 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);
 
-	pcpue_ptr = __alloc_bootmem_nopanic(
-					num_possible_cpus() * pcpue_unit_size,
-					PAGE_SIZE, __pa(MAX_DMA_ADDRESS));
-	if (!pcpue_ptr)
+	chunk_size = pcpue_unit_size * num_possible_cpus();
+
+	pcpue_ptr = __alloc_bootmem_nopanic(chunk_size, PAGE_SIZE,
+					    __pa(MAX_DMA_ADDRESS));
+	if (!pcpue_ptr) {
+		pr_warning("PERCPU: failed to allocate %zu bytes for "
+			   "embedding\n", chunk_size);
 		return -ENOMEM;
+	}
 
 	/* return the leftover and copy */
 	for_each_possible_cpu(cpu) {
-- 
1.6.0.2

[PATCH 7/7] x86: ensure percpu lpage doesn't consume too much vmalloc space

[Tejun Heo]

On extreme configuration (e.g. 32bit 32-way NUMA machine), lpage
percpu first chunk allocator can consume too much of vmalloc space.
Make it fall back to 4k allocator if the consumption goes over 20%.

[ Impact: add sanity check for lpage percpu first chunk allocator ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Jan Beulich <JBeulich@novell.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Ingo Molnar <mingo@elte.hu>
---
 arch/x86/kernel/setup_percpu.c |   18 +++++++++++++++---
 1 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c
index 165ebd5..29a3eef 100644
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -163,9 +163,21 @@ static ssize_t __init setup_pcpu_lpage(size_t static_size, bool chosen)
 	int i, j;
 	ssize_t ret;
 
-	/* on non-NUMA, embedding is better */
-	if (!chosen && !pcpu_need_numa())
-		return -EINVAL;
+	if (!chosen) {
+		size_t vm_size = VMALLOC_END - VMALLOC_START;
+		size_t tot_size = num_possible_cpus() * PMD_SIZE;
+
+		/* on non-NUMA, embedding is better */
+		if (!pcpu_need_numa())
+			return -EINVAL;
+
+		/* don't consume more than 20% of vmalloc area */
+		if (tot_size > vm_size / 5) {
+			pr_info("PERCPU: too large chunk size %zuMB for "
+				"large page remap\n", tot_size >> 20);
+			return -EINVAL;
+		}
+	}
 
 	/* need PSE */
 	if (!cpu_has_pse) {
-- 
1.6.0.2