[PATCH v2 0/4] arm64: put objects into proper sections

[PATCH v2 0/4] arm64: put objects into proper sections

[Jisheng Zhang]

This series tries to put objects into proper sections.

patch1 puts alloc_vectors_page() into .init section. This is a clean up
patch.
patch2 constify vm_special_mapping used for aarch32 vectors page.
patch3 fix the incorrect placement of __initdata and __read_mostly
patch4 apply __ro_after_init to some objects

Previously I only want to mark vdso_pages, vdso_spec, vectors_page and
cpu_ops as __read_mostly for performance reason. Then inspired by
Kees's patch[1], I think __ro_after_init is better.

[1] http://www.spinics.net/lists/arm-kernel/msg523188.html

Changes since v1:
  - use __ro_after_init instead of __read_mostly
  - find more objects to be suitable for __ro_after_init
  - add one more patch to fix the incorrect placement of __initdata and
    __read_mostly

Jisheng Zhang (4):
  arm64: vdso: add __init section marker to alloc_vectors_page
  arm64: vdso: constify vm_special_mapping used for aarch32 vectors page
  arm64: kaslr: Fix incorrect placement of __initdata and __read_mostly
  arm64: apply __ro_after_init to some objects

 arch/arm64/kernel/cpu_ops.c |  2 +-
 arch/arm64/kernel/kaslr.c   |  4 ++--
 arch/arm64/kernel/vdso.c    | 31 +++++++++++++++----------------
 arch/arm64/mm/dma-mapping.c |  2 +-
 arch/arm64/mm/init.c        |  4 ++--
 arch/arm64/mm/mmu.c         |  2 +-
 6 files changed, 22 insertions(+), 23 deletions(-)

-- 
2.8.1

[PATCH v2 0/4] arm64: put objects into proper sections

[Jisheng Zhang]

This series tries to put objects into proper sections.

patch1 puts alloc_vectors_page() into .init section. This is a clean up
patch.
patch2 constify vm_special_mapping used for aarch32 vectors page.
patch3 fix the incorrect placement of __initdata and __read_mostly
patch4 apply __ro_after_init to some objects

Previously I only want to mark vdso_pages, vdso_spec, vectors_page and
cpu_ops as __read_mostly for performance reason. Then inspired by
Kees's patch[1], I think __ro_after_init is better.

[1] http://www.spinics.net/lists/arm-kernel/msg523188.html

Changes since v1:
  - use __ro_after_init instead of __read_mostly
  - find more objects to be suitable for __ro_after_init
  - add one more patch to fix the incorrect placement of __initdata and
    __read_mostly

Jisheng Zhang (4):
  arm64: vdso: add __init section marker to alloc_vectors_page
  arm64: vdso: constify vm_special_mapping used for aarch32 vectors page
  arm64: kaslr: Fix incorrect placement of __initdata and __read_mostly
  arm64: apply __ro_after_init to some objects

 arch/arm64/kernel/cpu_ops.c |  2 +-
 arch/arm64/kernel/kaslr.c   |  4 ++--
 arch/arm64/kernel/vdso.c    | 31 +++++++++++++++----------------
 arch/arm64/mm/dma-mapping.c |  2 +-
 arch/arm64/mm/init.c        |  4 ++--
 arch/arm64/mm/mmu.c         |  2 +-
 6 files changed, 22 insertions(+), 23 deletions(-)

-- 
2.8.1

[PATCH v2 1/4] arm64: vdso: add __init section marker to alloc_vectors_page

[Jisheng Zhang]

It is not needed after booting, this patch moves the alloc_vectors_page
function to the __init section.

Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
---
 arch/arm64/kernel/vdso.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index 076312b..e320e8f 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -55,7 +55,7 @@ struct vdso_data *vdso_data = &vdso_data_store.data;
  */
 static struct page *vectors_page[1];
 
-static int alloc_vectors_page(void)
+static int __init alloc_vectors_page(void)
 {
 	extern char __kuser_helper_start[], __kuser_helper_end[];
 	extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[];
-- 
2.8.1

[PATCH v2 1/4] arm64: vdso: add __init section marker to alloc_vectors_page

[Jisheng Zhang]

It is not needed after booting, this patch moves the alloc_vectors_page
function to the __init section.

Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
---
 arch/arm64/kernel/vdso.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index 076312b..e320e8f 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -55,7 +55,7 @@ struct vdso_data *vdso_data = &vdso_data_store.data;
  */
 static struct page *vectors_page[1];
 
-static int alloc_vectors_page(void)
+static int __init alloc_vectors_page(void)
 {
 	extern char __kuser_helper_start[], __kuser_helper_end[];
 	extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[];
-- 
2.8.1

[PATCH v2 2/4] arm64: vdso: constify vm_special_mapping used for aarch32 vectors page

[Jisheng Zhang]

The vm_special_mapping spec which is used for aarch32 vectors page is
never modified, so mark it as const.

Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
---
 arch/arm64/kernel/vdso.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index e320e8f..10ad8ab 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -88,7 +88,7 @@ int aarch32_setup_vectors_page(struct linux_binprm *bprm, int uses_interp)
 {
 	struct mm_struct *mm = current->mm;
 	unsigned long addr = AARCH32_VECTORS_BASE;
-	static struct vm_special_mapping spec = {
+	static const struct vm_special_mapping spec = {
 		.name	= "[vectors]",
 		.pages	= vectors_page,
 
-- 
2.8.1

[PATCH v2 2/4] arm64: vdso: constify vm_special_mapping used for aarch32 vectors page

[Jisheng Zhang]

The vm_special_mapping spec which is used for aarch32 vectors page is
never modified, so mark it as const.

Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
---
 arch/arm64/kernel/vdso.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index e320e8f..10ad8ab 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -88,7 +88,7 @@ int aarch32_setup_vectors_page(struct linux_binprm *bprm, int uses_interp)
 {
 	struct mm_struct *mm = current->mm;
 	unsigned long addr = AARCH32_VECTORS_BASE;
-	static struct vm_special_mapping spec = {
+	static const struct vm_special_mapping spec = {
 		.name	= "[vectors]",
 		.pages	= vectors_page,
 
-- 
2.8.1

[PATCH v2 3/4] arm64: kaslr: Fix incorrect placement of __initdata and __read_mostly

[Jisheng Zhang]

__initdata and __read_mostly should be placed after the variable name
for the variable to be placed in the intended section.

Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
---
 arch/arm64/kernel/kaslr.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
index b054691..8ebabc4 100644
--- a/arch/arm64/kernel/kaslr.c
+++ b/arch/arm64/kernel/kaslr.c
@@ -20,8 +20,8 @@
 #include <asm/pgtable.h>
 #include <asm/sections.h>
 
-u64 __read_mostly module_alloc_base;
-u16 __initdata memstart_offset_seed;
+u64 module_alloc_base __read_mostly;
+u16 memstart_offset_seed __initdata;
 
 static __init u64 get_kaslr_seed(void *fdt)
 {
-- 
2.8.1

[PATCH v2 3/4] arm64: kaslr: Fix incorrect placement of __initdata and __read_mostly

[Jisheng Zhang]

__initdata and __read_mostly should be placed after the variable name
for the variable to be placed in the intended section.

Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
---
 arch/arm64/kernel/kaslr.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
index b054691..8ebabc4 100644
--- a/arch/arm64/kernel/kaslr.c
+++ b/arch/arm64/kernel/kaslr.c
@@ -20,8 +20,8 @@
 #include <asm/pgtable.h>
 #include <asm/sections.h>
 
-u64 __read_mostly module_alloc_base;
-u16 __initdata memstart_offset_seed;
+u64 module_alloc_base __read_mostly;
+u16 memstart_offset_seed __initdata;
 
 static __init u64 get_kaslr_seed(void *fdt)
 {
-- 
2.8.1

[PATCH v2 4/4] arm64: apply __ro_after_init to some objects

[Jisheng Zhang]

These objects are set during initialization, thereafter are read only.

Previously I only want to mark vdso_pages, vdso_spec, vectors_page and
cpu_ops as __read_mostly from performance point of view. Then inspired
by Kees's patch[1] to apply more __ro_after_init for arm, I think it's
better to mark them as __ro_after_init. What's more, I find some more
objects are also read only after init. So apply __ro_after_init to all
of them.

This patch also removes global vdso_pagelist and tries to clean up
vdso_spec[] assignment code.

[1] http://www.spinics.net/lists/arm-kernel/msg523188.html

Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
---
 arch/arm64/kernel/cpu_ops.c |  2 +-
 arch/arm64/kernel/kaslr.c   |  2 +-
 arch/arm64/kernel/vdso.c    | 27 +++++++++++++--------------
 arch/arm64/mm/dma-mapping.c |  2 +-
 arch/arm64/mm/init.c        |  4 ++--
 arch/arm64/mm/mmu.c         |  2 +-
 6 files changed, 19 insertions(+), 20 deletions(-)

diff --git a/arch/arm64/kernel/cpu_ops.c b/arch/arm64/kernel/cpu_ops.c
index c7cfb8f..6d32d1a 100644
--- a/arch/arm64/kernel/cpu_ops.c
+++ b/arch/arm64/kernel/cpu_ops.c
@@ -28,7 +28,7 @@ extern const struct cpu_operations smp_spin_table_ops;
 extern const struct cpu_operations acpi_parking_protocol_ops;
 extern const struct cpu_operations cpu_psci_ops;
 
-const struct cpu_operations *cpu_ops[NR_CPUS];
+const struct cpu_operations *cpu_ops[NR_CPUS] __ro_after_init;
 
 static const struct cpu_operations *dt_supported_cpu_ops[] __initconst = {
 	&smp_spin_table_ops,
diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
index 8ebabc4..93c47e1 100644
--- a/arch/arm64/kernel/kaslr.c
+++ b/arch/arm64/kernel/kaslr.c
@@ -20,7 +20,7 @@
 #include <asm/pgtable.h>
 #include <asm/sections.h>
 
-u64 module_alloc_base __read_mostly;
+u64 module_alloc_base __ro_after_init;
 u16 memstart_offset_seed __initdata;
 
 static __init u64 get_kaslr_seed(void *fdt)
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index 10ad8ab..0af41de 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -37,8 +37,7 @@
 #include <asm/vdso_datapage.h>
 
 extern char vdso_start, vdso_end;
-static unsigned long vdso_pages;
-static struct page **vdso_pagelist;
+static unsigned long vdso_pages __ro_after_init;
 
 /*
  * The vDSO data page.
@@ -53,7 +52,7 @@ struct vdso_data *vdso_data = &vdso_data_store.data;
 /*
  * Create and map the vectors page for AArch32 tasks.
  */
-static struct page *vectors_page[1];
+static struct page *vectors_page[1] __ro_after_init;
 
 static int __init alloc_vectors_page(void)
 {
@@ -110,11 +109,19 @@ int aarch32_setup_vectors_page(struct linux_binprm *bprm, int uses_interp)
 }
 #endif /* CONFIG_COMPAT */
 
-static struct vm_special_mapping vdso_spec[2];
+static struct vm_special_mapping vdso_spec[2] __ro_after_init = {
+	{
+		.name	= "[vvar]",
+	},
+	{
+		.name	= "[vdso]",
+	},
+};
 
 static int __init vdso_init(void)
 {
 	int i;
+	struct page **vdso_pagelist;
 
 	if (memcmp(&vdso_start, "\177ELF", 4)) {
 		pr_err("vDSO is not a valid ELF object!\n");
@@ -138,16 +145,8 @@ static int __init vdso_init(void)
 	for (i = 0; i < vdso_pages; i++)
 		vdso_pagelist[i + 1] = pfn_to_page(PHYS_PFN(__pa(&vdso_start)) + i);
 
-	/* Populate the special mapping structures */
-	vdso_spec[0] = (struct vm_special_mapping) {
-		.name	= "[vvar]",
-		.pages	= vdso_pagelist,
-	};
-
-	vdso_spec[1] = (struct vm_special_mapping) {
-		.name	= "[vdso]",
-		.pages	= &vdso_pagelist[1],
-	};
+	vdso_spec[0].pages = vdso_pagelist;
+	vdso_spec[1].pages = &vdso_pagelist[1];
 
 	return 0;
 }
diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index c4284c4..59d44e7 100644
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -30,7 +30,7 @@
 
 #include <asm/cacheflush.h>
 
-static int swiotlb __read_mostly;
+static int swiotlb __ro_after_init;
 
 static pgprot_t __get_dma_pgprot(unsigned long attrs, pgprot_t prot,
 				 bool coherent)
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index bbb7ee7..e8b81ea 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -55,8 +55,8 @@
  * executes, which assigns it its actual value. So use a default value
  * that cannot be mistaken for a real physical address.
  */
-s64 memstart_addr __read_mostly = -1;
-phys_addr_t arm64_dma_phys_limit __read_mostly;
+s64 memstart_addr __ro_after_init = -1;
+phys_addr_t arm64_dma_phys_limit __ro_after_init;
 
 #ifdef CONFIG_BLK_DEV_INITRD
 static int __init early_initrd(char *p)
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 4989948..6029bed 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -46,7 +46,7 @@
 
 u64 idmap_t0sz = TCR_T0SZ(VA_BITS);
 
-u64 kimage_voffset __read_mostly;
+u64 kimage_voffset __ro_after_init;
 EXPORT_SYMBOL(kimage_voffset);
 
 /*
-- 
2.8.1

[PATCH v2 4/4] arm64: apply __ro_after_init to some objects

[Jisheng Zhang]

These objects are set during initialization, thereafter are read only.

Previously I only want to mark vdso_pages, vdso_spec, vectors_page and
cpu_ops as __read_mostly from performance point of view. Then inspired
by Kees's patch[1] to apply more __ro_after_init for arm, I think it's
better to mark them as __ro_after_init. What's more, I find some more
objects are also read only after init. So apply __ro_after_init to all
of them.

This patch also removes global vdso_pagelist and tries to clean up
vdso_spec[] assignment code.

[1] http://www.spinics.net/lists/arm-kernel/msg523188.html

Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
---
 arch/arm64/kernel/cpu_ops.c |  2 +-
 arch/arm64/kernel/kaslr.c   |  2 +-
 arch/arm64/kernel/vdso.c    | 27 +++++++++++++--------------
 arch/arm64/mm/dma-mapping.c |  2 +-
 arch/arm64/mm/init.c        |  4 ++--
 arch/arm64/mm/mmu.c         |  2 +-
 6 files changed, 19 insertions(+), 20 deletions(-)

diff --git a/arch/arm64/kernel/cpu_ops.c b/arch/arm64/kernel/cpu_ops.c
index c7cfb8f..6d32d1a 100644
--- a/arch/arm64/kernel/cpu_ops.c
+++ b/arch/arm64/kernel/cpu_ops.c
@@ -28,7 +28,7 @@ extern const struct cpu_operations smp_spin_table_ops;
 extern const struct cpu_operations acpi_parking_protocol_ops;
 extern const struct cpu_operations cpu_psci_ops;
 
-const struct cpu_operations *cpu_ops[NR_CPUS];
+const struct cpu_operations *cpu_ops[NR_CPUS] __ro_after_init;
 
 static const struct cpu_operations *dt_supported_cpu_ops[] __initconst = {
 	&smp_spin_table_ops,
diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
index 8ebabc4..93c47e1 100644
--- a/arch/arm64/kernel/kaslr.c
+++ b/arch/arm64/kernel/kaslr.c
@@ -20,7 +20,7 @@
 #include <asm/pgtable.h>
 #include <asm/sections.h>
 
-u64 module_alloc_base __read_mostly;
+u64 module_alloc_base __ro_after_init;
 u16 memstart_offset_seed __initdata;
 
 static __init u64 get_kaslr_seed(void *fdt)
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index 10ad8ab..0af41de 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -37,8 +37,7 @@
 #include <asm/vdso_datapage.h>
 
 extern char vdso_start, vdso_end;
-static unsigned long vdso_pages;
-static struct page **vdso_pagelist;
+static unsigned long vdso_pages __ro_after_init;
 
 /*
  * The vDSO data page.
@@ -53,7 +52,7 @@ struct vdso_data *vdso_data = &vdso_data_store.data;
 /*
  * Create and map the vectors page for AArch32 tasks.
  */
-static struct page *vectors_page[1];
+static struct page *vectors_page[1] __ro_after_init;
 
 static int __init alloc_vectors_page(void)
 {
@@ -110,11 +109,19 @@ int aarch32_setup_vectors_page(struct linux_binprm *bprm, int uses_interp)
 }
 #endif /* CONFIG_COMPAT */
 
-static struct vm_special_mapping vdso_spec[2];
+static struct vm_special_mapping vdso_spec[2] __ro_after_init = {
+	{
+		.name	= "[vvar]",
+	},
+	{
+		.name	= "[vdso]",
+	},
+};
 
 static int __init vdso_init(void)
 {
 	int i;
+	struct page **vdso_pagelist;
 
 	if (memcmp(&vdso_start, "\177ELF", 4)) {
 		pr_err("vDSO is not a valid ELF object!\n");
@@ -138,16 +145,8 @@ static int __init vdso_init(void)
 	for (i = 0; i < vdso_pages; i++)
 		vdso_pagelist[i + 1] = pfn_to_page(PHYS_PFN(__pa(&vdso_start)) + i);
 
-	/* Populate the special mapping structures */
-	vdso_spec[0] = (struct vm_special_mapping) {
-		.name	= "[vvar]",
-		.pages	= vdso_pagelist,
-	};
-
-	vdso_spec[1] = (struct vm_special_mapping) {
-		.name	= "[vdso]",
-		.pages	= &vdso_pagelist[1],
-	};
+	vdso_spec[0].pages = vdso_pagelist;
+	vdso_spec[1].pages = &vdso_pagelist[1];
 
 	return 0;
 }
diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index c4284c4..59d44e7 100644
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -30,7 +30,7 @@
 
 #include <asm/cacheflush.h>
 
-static int swiotlb __read_mostly;
+static int swiotlb __ro_after_init;
 
 static pgprot_t __get_dma_pgprot(unsigned long attrs, pgprot_t prot,
 				 bool coherent)
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index bbb7ee7..e8b81ea 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -55,8 +55,8 @@
  * executes, which assigns it its actual value. So use a default value
  * that cannot be mistaken for a real physical address.
  */
-s64 memstart_addr __read_mostly = -1;
-phys_addr_t arm64_dma_phys_limit __read_mostly;
+s64 memstart_addr __ro_after_init = -1;
+phys_addr_t arm64_dma_phys_limit __ro_after_init;
 
 #ifdef CONFIG_BLK_DEV_INITRD
 static int __init early_initrd(char *p)
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 4989948..6029bed 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -46,7 +46,7 @@
 
 u64 idmap_t0sz = TCR_T0SZ(VA_BITS);
 
-u64 kimage_voffset __read_mostly;
+u64 kimage_voffset __ro_after_init;
 EXPORT_SYMBOL(kimage_voffset);
 
 /*
-- 
2.8.1

Re: [PATCH v2 4/4] arm64: apply __ro_after_init to some objects

[Mark Rutland]

Hi,

On Thu, Aug 11, 2016 at 09:36:49PM +0800, Jisheng Zhang wrote:
> These objects are set during initialization, thereafter are read only.
> 
> Previously I only want to mark vdso_pages, vdso_spec, vectors_page and
> cpu_ops as __read_mostly from performance point of view. Then inspired
> by Kees's patch[1] to apply more __ro_after_init for arm, I think it's
> better to mark them as __ro_after_init. What's more, I find some more
> objects are also read only after init. So apply __ro_after_init to all
> of them.
> 
> This patch also removes global vdso_pagelist and tries to clean up
> vdso_spec[] assignment code.
> 
> [1] http://www.spinics.net/lists/arm-kernel/msg523188.html
> 
> Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
> ---
>  arch/arm64/kernel/cpu_ops.c |  2 +-
>  arch/arm64/kernel/kaslr.c   |  2 +-
>  arch/arm64/kernel/vdso.c    | 27 +++++++++++++--------------
>  arch/arm64/mm/dma-mapping.c |  2 +-
>  arch/arm64/mm/init.c        |  4 ++--
>  arch/arm64/mm/mmu.c         |  2 +-
>  6 files changed, 19 insertions(+), 20 deletions(-)
> 
> diff --git a/arch/arm64/kernel/cpu_ops.c b/arch/arm64/kernel/cpu_ops.c
> index c7cfb8f..6d32d1a 100644
> --- a/arch/arm64/kernel/cpu_ops.c
> +++ b/arch/arm64/kernel/cpu_ops.c
> @@ -28,7 +28,7 @@ extern const struct cpu_operations smp_spin_table_ops;
>  extern const struct cpu_operations acpi_parking_protocol_ops;
>  extern const struct cpu_operations cpu_psci_ops;
>  
> -const struct cpu_operations *cpu_ops[NR_CPUS];
> +const struct cpu_operations *cpu_ops[NR_CPUS] __ro_after_init;

It looks like we need to include <linux/cache.h> for __ro_after_init.
While we seem to get that via some transitive include, that's not
guaranteed to remain the case, and it's not something we should rely
upon.

Please explicitly include <linux/cache.h> when __ro_after_init is added.

> -	/* Populate the special mapping structures */
> -	vdso_spec[0] = (struct vm_special_mapping) {
> -		.name	= "[vvar]",
> -		.pages	= vdso_pagelist,
> -	};
> -
> -	vdso_spec[1] = (struct vm_special_mapping) {
> -		.name	= "[vdso]",
> -		.pages	= &vdso_pagelist[1],
> -	};
> +	vdso_spec[0].pages = vdso_pagelist;
> +	vdso_spec[1].pages = &vdso_pagelist[1];

While the original code was also this way, could we please make these a
little more consistent? e.g.

	vdso_spec[0].pages = &vdso_pagelist[0];
	vdso_spec[1].pages = &vdso_pagelist[1];

That way it raises few false alarms for anyone looking at the code.

Otherwise, this patch looks largely fine.

Thanks,
Mark.

[PATCH v2 4/4] arm64: apply __ro_after_init to some objects

[Mark Rutland]

Hi,

On Thu, Aug 11, 2016 at 09:36:49PM +0800, Jisheng Zhang wrote:
> These objects are set during initialization, thereafter are read only.
> 
> Previously I only want to mark vdso_pages, vdso_spec, vectors_page and
> cpu_ops as __read_mostly from performance point of view. Then inspired
> by Kees's patch[1] to apply more __ro_after_init for arm, I think it's
> better to mark them as __ro_after_init. What's more, I find some more
> objects are also read only after init. So apply __ro_after_init to all
> of them.
> 
> This patch also removes global vdso_pagelist and tries to clean up
> vdso_spec[] assignment code.
> 
> [1] http://www.spinics.net/lists/arm-kernel/msg523188.html
> 
> Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
> ---
>  arch/arm64/kernel/cpu_ops.c |  2 +-
>  arch/arm64/kernel/kaslr.c   |  2 +-
>  arch/arm64/kernel/vdso.c    | 27 +++++++++++++--------------
>  arch/arm64/mm/dma-mapping.c |  2 +-
>  arch/arm64/mm/init.c        |  4 ++--
>  arch/arm64/mm/mmu.c         |  2 +-
>  6 files changed, 19 insertions(+), 20 deletions(-)
> 
> diff --git a/arch/arm64/kernel/cpu_ops.c b/arch/arm64/kernel/cpu_ops.c
> index c7cfb8f..6d32d1a 100644
> --- a/arch/arm64/kernel/cpu_ops.c
> +++ b/arch/arm64/kernel/cpu_ops.c
> @@ -28,7 +28,7 @@ extern const struct cpu_operations smp_spin_table_ops;
>  extern const struct cpu_operations acpi_parking_protocol_ops;
>  extern const struct cpu_operations cpu_psci_ops;
>  
> -const struct cpu_operations *cpu_ops[NR_CPUS];
> +const struct cpu_operations *cpu_ops[NR_CPUS] __ro_after_init;

It looks like we need to include <linux/cache.h> for __ro_after_init.
While we seem to get that via some transitive include, that's not
guaranteed to remain the case, and it's not something we should rely
upon.

Please explicitly include <linux/cache.h> when __ro_after_init is added.

> -	/* Populate the special mapping structures */
> -	vdso_spec[0] = (struct vm_special_mapping) {
> -		.name	= "[vvar]",
> -		.pages	= vdso_pagelist,
> -	};
> -
> -	vdso_spec[1] = (struct vm_special_mapping) {
> -		.name	= "[vdso]",
> -		.pages	= &vdso_pagelist[1],
> -	};
> +	vdso_spec[0].pages = vdso_pagelist;
> +	vdso_spec[1].pages = &vdso_pagelist[1];

While the original code was also this way, could we please make these a
little more consistent? e.g.

	vdso_spec[0].pages = &vdso_pagelist[0];
	vdso_spec[1].pages = &vdso_pagelist[1];

That way it raises few false alarms for anyone looking at the code.

Otherwise, this patch looks largely fine.

Thanks,
Mark.