* [PATCH v2] powerpc/s64: Clarify that radix lacks DEBUG_PAGEALLOC
@ 2021-10-13 21:34 Joel Stanley
2021-10-14 8:45 ` Christophe Leroy
2021-11-02 10:11 ` Michael Ellerman
0 siblings, 2 replies; 4+ messages in thread
From: Joel Stanley @ 2021-10-13 21:34 UTC (permalink / raw)
To: Jordan Niethe, Christophe Leroy; +Cc: linuxppc-dev
The page_alloc.c code will call into __kernel_map_pages when
DEBUG_PAGEALLOC is configured and enabled.
As the implementation assumes hash, this should crash spectacularly if
not for a bit of luck in __kernel_map_pages. In this function
linear_map_hash_count is always zero, the for loop exits without doing
any damage.
There are no other platforms that determine if they support
debug_pagealloc at runtime. Instead of adding code to mm/page_alloc.c to
do that, this change turns the map/unmap into a noop when in radix
mode and prints a warning once.
Signed-off-by: Joel Stanley <joel@jms.id.au>
---
v2: Put __kernel_map_pages in pgtable.h
arch/powerpc/include/asm/book3s/64/hash.h | 2 ++
arch/powerpc/include/asm/book3s/64/pgtable.h | 11 +++++++++++
arch/powerpc/include/asm/book3s/64/radix.h | 3 +++
arch/powerpc/mm/book3s64/hash_utils.c | 2 +-
arch/powerpc/mm/book3s64/radix_pgtable.c | 7 +++++++
5 files changed, 24 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/include/asm/book3s/64/hash.h b/arch/powerpc/include/asm/book3s/64/hash.h
index d959b0195ad9..674fe0e890dc 100644
--- a/arch/powerpc/include/asm/book3s/64/hash.h
+++ b/arch/powerpc/include/asm/book3s/64/hash.h
@@ -255,6 +255,8 @@ int hash__create_section_mapping(unsigned long start, unsigned long end,
int nid, pgprot_t prot);
int hash__remove_section_mapping(unsigned long start, unsigned long end);
+void hash__kernel_map_pages(struct page *page, int numpages, int enable);
+
#endif /* !__ASSEMBLY__ */
#endif /* __KERNEL__ */
#endif /* _ASM_POWERPC_BOOK3S_64_HASH_H */
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 5d34a8646f08..265661ded238 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -1101,6 +1101,17 @@ static inline void vmemmap_remove_mapping(unsigned long start,
}
#endif
+#ifdef CONFIG_DEBUG_PAGEALLOC
+static inline void __kernel_map_pages(struct page *page, int numpages, int enable)
+{
+ if (radix_enabled()) {
+ radix__kernel_map_pages(page, numpages, enable);
+ return;
+ }
+ hash__kernel_map_pages(page, numpages, enable);
+}
+#endif
+
static inline pte_t pmd_pte(pmd_t pmd)
{
return __pte_raw(pmd_raw(pmd));
diff --git a/arch/powerpc/include/asm/book3s/64/radix.h b/arch/powerpc/include/asm/book3s/64/radix.h
index 59cab558e2f0..d090d9612348 100644
--- a/arch/powerpc/include/asm/book3s/64/radix.h
+++ b/arch/powerpc/include/asm/book3s/64/radix.h
@@ -316,5 +316,8 @@ int radix__create_section_mapping(unsigned long start, unsigned long end,
int nid, pgprot_t prot);
int radix__remove_section_mapping(unsigned long start, unsigned long end);
#endif /* CONFIG_MEMORY_HOTPLUG */
+
+void radix__kernel_map_pages(struct page *page, int numpages, int enable);
+
#endif /* __ASSEMBLY__ */
#endif
diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c
index c145776d3ae5..cfd45245d009 100644
--- a/arch/powerpc/mm/book3s64/hash_utils.c
+++ b/arch/powerpc/mm/book3s64/hash_utils.c
@@ -1988,7 +1988,7 @@ static void kernel_unmap_linear_page(unsigned long vaddr, unsigned long lmi)
mmu_kernel_ssize, 0);
}
-void __kernel_map_pages(struct page *page, int numpages, int enable)
+void hash__kernel_map_pages(struct page *page, int numpages, int enable)
{
unsigned long flags, vaddr, lmi;
int i;
diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c
index ae20add7954a..83b33418ad28 100644
--- a/arch/powerpc/mm/book3s64/radix_pgtable.c
+++ b/arch/powerpc/mm/book3s64/radix_pgtable.c
@@ -920,6 +920,13 @@ void __meminit radix__vmemmap_remove_mapping(unsigned long start, unsigned long
#endif
#endif
+#ifdef CONFIG_DEBUG_PAGEALLOC
+void radix__kernel_map_pages(struct page *page, int numpages, int enable)
+{
+ pr_warn_once("DEBUG_PAGEALLOC not supported in radix mode\n");
+}
+#endif
+
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
unsigned long radix__pmd_hugepage_update(struct mm_struct *mm, unsigned long addr,
--
2.33.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v2] powerpc/s64: Clarify that radix lacks DEBUG_PAGEALLOC
2021-10-13 21:34 [PATCH v2] powerpc/s64: Clarify that radix lacks DEBUG_PAGEALLOC Joel Stanley
@ 2021-10-14 8:45 ` Christophe Leroy
2021-10-15 10:41 ` Michael Ellerman
2021-11-02 10:11 ` Michael Ellerman
1 sibling, 1 reply; 4+ messages in thread
From: Christophe Leroy @ 2021-10-14 8:45 UTC (permalink / raw)
To: Joel Stanley, Jordan Niethe; +Cc: linuxppc-dev
Le 13/10/2021 à 23:34, Joel Stanley a écrit :
> The page_alloc.c code will call into __kernel_map_pages when
> DEBUG_PAGEALLOC is configured and enabled.
>
> As the implementation assumes hash, this should crash spectacularly if
> not for a bit of luck in __kernel_map_pages. In this function
> linear_map_hash_count is always zero, the for loop exits without doing
> any damage.
>
> There are no other platforms that determine if they support
> debug_pagealloc at runtime. Instead of adding code to mm/page_alloc.c to
> do that, this change turns the map/unmap into a noop when in radix
> mode and prints a warning once.
>
> Signed-off-by: Joel Stanley <joel@jms.id.au>
> ---
> v2: Put __kernel_map_pages in pgtable.h
>
> arch/powerpc/include/asm/book3s/64/hash.h | 2 ++
> arch/powerpc/include/asm/book3s/64/pgtable.h | 11 +++++++++++
> arch/powerpc/include/asm/book3s/64/radix.h | 3 +++
> arch/powerpc/mm/book3s64/hash_utils.c | 2 +-
> arch/powerpc/mm/book3s64/radix_pgtable.c | 7 +++++++
> 5 files changed, 24 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/include/asm/book3s/64/hash.h b/arch/powerpc/include/asm/book3s/64/hash.h
> index d959b0195ad9..674fe0e890dc 100644
> --- a/arch/powerpc/include/asm/book3s/64/hash.h
> +++ b/arch/powerpc/include/asm/book3s/64/hash.h
> @@ -255,6 +255,8 @@ int hash__create_section_mapping(unsigned long start, unsigned long end,
> int nid, pgprot_t prot);
> int hash__remove_section_mapping(unsigned long start, unsigned long end);
>
> +void hash__kernel_map_pages(struct page *page, int numpages, int enable);
> +
> #endif /* !__ASSEMBLY__ */
> #endif /* __KERNEL__ */
> #endif /* _ASM_POWERPC_BOOK3S_64_HASH_H */
> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
> index 5d34a8646f08..265661ded238 100644
> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
> @@ -1101,6 +1101,17 @@ static inline void vmemmap_remove_mapping(unsigned long start,
> }
> #endif
>
> +#ifdef CONFIG_DEBUG_PAGEALLOC
> +static inline void __kernel_map_pages(struct page *page, int numpages, int enable)
> +{
> + if (radix_enabled()) {
> + radix__kernel_map_pages(page, numpages, enable);
> + return;
> + }
> + hash__kernel_map_pages(page, numpages, enable);
I'd have prefered something like below
if (radix_enabled())
radix__kernel_map_pages(page, numpages, enable);
else
hash__kernel_map_pages(page, numpages, enable);
But regardless,
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> +}
> +#endif
> +
> static inline pte_t pmd_pte(pmd_t pmd)
> {
> return __pte_raw(pmd_raw(pmd));
> diff --git a/arch/powerpc/include/asm/book3s/64/radix.h b/arch/powerpc/include/asm/book3s/64/radix.h
> index 59cab558e2f0..d090d9612348 100644
> --- a/arch/powerpc/include/asm/book3s/64/radix.h
> +++ b/arch/powerpc/include/asm/book3s/64/radix.h
> @@ -316,5 +316,8 @@ int radix__create_section_mapping(unsigned long start, unsigned long end,
> int nid, pgprot_t prot);
> int radix__remove_section_mapping(unsigned long start, unsigned long end);
> #endif /* CONFIG_MEMORY_HOTPLUG */
> +
> +void radix__kernel_map_pages(struct page *page, int numpages, int enable);
> +
> #endif /* __ASSEMBLY__ */
> #endif
> diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c
> index c145776d3ae5..cfd45245d009 100644
> --- a/arch/powerpc/mm/book3s64/hash_utils.c
> +++ b/arch/powerpc/mm/book3s64/hash_utils.c
> @@ -1988,7 +1988,7 @@ static void kernel_unmap_linear_page(unsigned long vaddr, unsigned long lmi)
> mmu_kernel_ssize, 0);
> }
>
> -void __kernel_map_pages(struct page *page, int numpages, int enable)
> +void hash__kernel_map_pages(struct page *page, int numpages, int enable)
> {
> unsigned long flags, vaddr, lmi;
> int i;
> diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c
> index ae20add7954a..83b33418ad28 100644
> --- a/arch/powerpc/mm/book3s64/radix_pgtable.c
> +++ b/arch/powerpc/mm/book3s64/radix_pgtable.c
> @@ -920,6 +920,13 @@ void __meminit radix__vmemmap_remove_mapping(unsigned long start, unsigned long
> #endif
> #endif
>
> +#ifdef CONFIG_DEBUG_PAGEALLOC
> +void radix__kernel_map_pages(struct page *page, int numpages, int enable)
> +{
> + pr_warn_once("DEBUG_PAGEALLOC not supported in radix mode\n");
> +}
> +#endif
> +
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>
> unsigned long radix__pmd_hugepage_update(struct mm_struct *mm, unsigned long addr,
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] powerpc/s64: Clarify that radix lacks DEBUG_PAGEALLOC
2021-10-14 8:45 ` Christophe Leroy
@ 2021-10-15 10:41 ` Michael Ellerman
0 siblings, 0 replies; 4+ messages in thread
From: Michael Ellerman @ 2021-10-15 10:41 UTC (permalink / raw)
To: Christophe Leroy, Joel Stanley, Jordan Niethe; +Cc: linuxppc-dev
Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> Le 13/10/2021 à 23:34, Joel Stanley a écrit :
>> The page_alloc.c code will call into __kernel_map_pages when
>> DEBUG_PAGEALLOC is configured and enabled.
>>
>> As the implementation assumes hash, this should crash spectacularly if
>> not for a bit of luck in __kernel_map_pages. In this function
>> linear_map_hash_count is always zero, the for loop exits without doing
>> any damage.
>>
>> There are no other platforms that determine if they support
>> debug_pagealloc at runtime. Instead of adding code to mm/page_alloc.c to
>> do that, this change turns the map/unmap into a noop when in radix
>> mode and prints a warning once.
>>
>> Signed-off-by: Joel Stanley <joel@jms.id.au>
>> ---
>> v2: Put __kernel_map_pages in pgtable.h
>>
>> arch/powerpc/include/asm/book3s/64/hash.h | 2 ++
>> arch/powerpc/include/asm/book3s/64/pgtable.h | 11 +++++++++++
>> arch/powerpc/include/asm/book3s/64/radix.h | 3 +++
>> arch/powerpc/mm/book3s64/hash_utils.c | 2 +-
>> arch/powerpc/mm/book3s64/radix_pgtable.c | 7 +++++++
>> 5 files changed, 24 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/powerpc/include/asm/book3s/64/hash.h b/arch/powerpc/include/asm/book3s/64/hash.h
>> index d959b0195ad9..674fe0e890dc 100644
>> --- a/arch/powerpc/include/asm/book3s/64/hash.h
>> +++ b/arch/powerpc/include/asm/book3s/64/hash.h
>> @@ -255,6 +255,8 @@ int hash__create_section_mapping(unsigned long start, unsigned long end,
>> int nid, pgprot_t prot);
>> int hash__remove_section_mapping(unsigned long start, unsigned long end);
>>
>> +void hash__kernel_map_pages(struct page *page, int numpages, int enable);
>> +
>> #endif /* !__ASSEMBLY__ */
>> #endif /* __KERNEL__ */
>> #endif /* _ASM_POWERPC_BOOK3S_64_HASH_H */
>> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
>> index 5d34a8646f08..265661ded238 100644
>> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
>> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
>> @@ -1101,6 +1101,17 @@ static inline void vmemmap_remove_mapping(unsigned long start,
>> }
>> #endif
>>
>> +#ifdef CONFIG_DEBUG_PAGEALLOC
>> +static inline void __kernel_map_pages(struct page *page, int numpages, int enable)
>> +{
>> + if (radix_enabled()) {
>> + radix__kernel_map_pages(page, numpages, enable);
>> + return;
>> + }
>> + hash__kernel_map_pages(page, numpages, enable);
>
> I'd have prefered something like below
>
> if (radix_enabled())
> radix__kernel_map_pages(page, numpages, enable);
> else
> hash__kernel_map_pages(page, numpages, enable);
I did that when applying.
cheers
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] powerpc/s64: Clarify that radix lacks DEBUG_PAGEALLOC
2021-10-13 21:34 [PATCH v2] powerpc/s64: Clarify that radix lacks DEBUG_PAGEALLOC Joel Stanley
2021-10-14 8:45 ` Christophe Leroy
@ 2021-11-02 10:11 ` Michael Ellerman
1 sibling, 0 replies; 4+ messages in thread
From: Michael Ellerman @ 2021-11-02 10:11 UTC (permalink / raw)
To: Jordan Niethe, Joel Stanley, Christophe Leroy; +Cc: linuxppc-dev
On Thu, 14 Oct 2021 08:04:38 +1030, Joel Stanley wrote:
> The page_alloc.c code will call into __kernel_map_pages when
> DEBUG_PAGEALLOC is configured and enabled.
>
> As the implementation assumes hash, this should crash spectacularly if
> not for a bit of luck in __kernel_map_pages. In this function
> linear_map_hash_count is always zero, the for loop exits without doing
> any damage.
>
> [...]
Applied to powerpc/next.
[1/1] powerpc/s64: Clarify that radix lacks DEBUG_PAGEALLOC
https://git.kernel.org/powerpc/c/4f703e7faa67a116016c4678fc88b507c12670c9
cheers
^ permalink raw reply [flat|nested] 4+ messages in thread
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2021-10-13 21:34 [PATCH v2] powerpc/s64: Clarify that radix lacks DEBUG_PAGEALLOC Joel Stanley
2021-10-14 8:45 ` Christophe Leroy
2021-10-15 10:41 ` Michael Ellerman
2021-11-02 10:11 ` Michael Ellerman
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