mm/pgtable/debug: Fix test validating architecture page table helpers
diff mbox series

Message ID 1892b37d1fd9a4ed39e76c4b999b6556077201c0.1568355752.git.christophe.leroy@c-s.fr
State New
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  • mm/pgtable/debug: Fix test validating architecture page table helpers
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Commit Message

Christophe Leroy Sept. 13, 2019, 6:23 a.m. UTC
Fix build failure on powerpc.

Fix preemption imbalance.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 mm/arch_pgtable_test.c | 3 +++
 1 file changed, 3 insertions(+)

Comments

Anshuman Khandual Sept. 13, 2019, 6:58 a.m. UTC | #1
On 09/13/2019 11:53 AM, Christophe Leroy wrote:
> Fix build failure on powerpc.
> 
> Fix preemption imbalance.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> ---
>  mm/arch_pgtable_test.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/mm/arch_pgtable_test.c b/mm/arch_pgtable_test.c
> index 8b4a92756ad8..f2b3c9ec35fa 100644
> --- a/mm/arch_pgtable_test.c
> +++ b/mm/arch_pgtable_test.c
> @@ -24,6 +24,7 @@
>  #include <linux/swap.h>
>  #include <linux/swapops.h>
>  #include <linux/sched/mm.h>
> +#include <linux/highmem.h>

This is okay.

>  #include <asm/pgalloc.h>
>  #include <asm/pgtable.h>
>  
> @@ -400,6 +401,8 @@ static int __init arch_pgtable_tests_init(void)
>  	p4d_clear_tests(p4dp);
>  	pgd_clear_tests(mm, pgdp);
>  
> +	pte_unmap(ptep);
> +

Now the preemption imbalance via pte_alloc_map() path i.e

pte_alloc_map() -> pte_offset_map() -> kmap_atomic()

Is not this very much powerpc 32 specific or this will be applicable
for all platform which uses kmap_XXX() to map high memory ?
Christophe Leroy Sept. 13, 2019, 7:03 a.m. UTC | #2
Le 13/09/2019 à 08:58, Anshuman Khandual a écrit :
> On 09/13/2019 11:53 AM, Christophe Leroy wrote:
>> Fix build failure on powerpc.
>>
>> Fix preemption imbalance.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
>> ---
>>   mm/arch_pgtable_test.c | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/mm/arch_pgtable_test.c b/mm/arch_pgtable_test.c
>> index 8b4a92756ad8..f2b3c9ec35fa 100644
>> --- a/mm/arch_pgtable_test.c
>> +++ b/mm/arch_pgtable_test.c
>> @@ -24,6 +24,7 @@
>>   #include <linux/swap.h>
>>   #include <linux/swapops.h>
>>   #include <linux/sched/mm.h>
>> +#include <linux/highmem.h>
> 
> This is okay.
> 
>>   #include <asm/pgalloc.h>
>>   #include <asm/pgtable.h>
>>   
>> @@ -400,6 +401,8 @@ static int __init arch_pgtable_tests_init(void)
>>   	p4d_clear_tests(p4dp);
>>   	pgd_clear_tests(mm, pgdp);
>>   
>> +	pte_unmap(ptep);
>> +
> 
> Now the preemption imbalance via pte_alloc_map() path i.e
> 
> pte_alloc_map() -> pte_offset_map() -> kmap_atomic()
> 
> Is not this very much powerpc 32 specific or this will be applicable
> for all platform which uses kmap_XXX() to map high memory ?
> 

See 
https://elixir.bootlin.com/linux/v5.3-rc8/source/include/linux/highmem.h#L91

I think it applies at least to all arches using the generic implementation.

Applies also to arm:
https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/arm/mm/highmem.c#L52

Applies also to mips:
https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/mips/mm/highmem.c#L47

Same on sparc:
https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/sparc/mm/highmem.c#L52

Same on x86:
https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/x86/mm/highmem_32.c#L34

I have not checked others, but I guess it is like that for all.

Christophe
Christophe Leroy Sept. 13, 2019, 7:11 a.m. UTC | #3
Le 13/09/2019 à 09:03, Christophe Leroy a écrit :
> 
> 
> Le 13/09/2019 à 08:58, Anshuman Khandual a écrit :
>> On 09/13/2019 11:53 AM, Christophe Leroy wrote:
>>> Fix build failure on powerpc.
>>>
>>> Fix preemption imbalance.
>>>
>>> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
>>> ---
>>>   mm/arch_pgtable_test.c | 3 +++
>>>   1 file changed, 3 insertions(+)
>>>
>>> diff --git a/mm/arch_pgtable_test.c b/mm/arch_pgtable_test.c
>>> index 8b4a92756ad8..f2b3c9ec35fa 100644
>>> --- a/mm/arch_pgtable_test.c
>>> +++ b/mm/arch_pgtable_test.c
>>> @@ -24,6 +24,7 @@
>>>   #include <linux/swap.h>
>>>   #include <linux/swapops.h>
>>>   #include <linux/sched/mm.h>
>>> +#include <linux/highmem.h>
>>
>> This is okay.
>>
>>>   #include <asm/pgalloc.h>
>>>   #include <asm/pgtable.h>
>>> @@ -400,6 +401,8 @@ static int __init arch_pgtable_tests_init(void)
>>>       p4d_clear_tests(p4dp);
>>>       pgd_clear_tests(mm, pgdp);
>>> +    pte_unmap(ptep);
>>> +
>>
>> Now the preemption imbalance via pte_alloc_map() path i.e
>>
>> pte_alloc_map() -> pte_offset_map() -> kmap_atomic()
>>
>> Is not this very much powerpc 32 specific or this will be applicable
>> for all platform which uses kmap_XXX() to map high memory ?
>>
> 
> See 
> https://elixir.bootlin.com/linux/v5.3-rc8/source/include/linux/highmem.h#L91 
> 
> 
> I think it applies at least to all arches using the generic implementation.
> 
> Applies also to arm:
> https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/arm/mm/highmem.c#L52
> 
> Applies also to mips:
> https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/mips/mm/highmem.c#L47
> 
> Same on sparc:
> https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/sparc/mm/highmem.c#L52 
> 
> 
> Same on x86:
> https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/x86/mm/highmem_32.c#L34 
> 
> 
> I have not checked others, but I guess it is like that for all.
> 


Seems like I answered too quickly. All kmap_atomic() do 
preempt_disable(), but not all pte_alloc_map() call kmap_atomic().

However, for instance ARM does:

https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/arm/include/asm/pgtable.h#L200

And X86 as well:

https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/x86/include/asm/pgtable_32.h#L51

Microblaze also:

https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/microblaze/include/asm/pgtable.h#L495

Christophe
Anshuman Khandual Sept. 13, 2019, 8:42 a.m. UTC | #4
On 09/13/2019 12:41 PM, Christophe Leroy wrote:
> 
> 
> Le 13/09/2019 à 09:03, Christophe Leroy a écrit :
>>
>>
>> Le 13/09/2019 à 08:58, Anshuman Khandual a écrit :
>>> On 09/13/2019 11:53 AM, Christophe Leroy wrote:
>>>> Fix build failure on powerpc.
>>>>
>>>> Fix preemption imbalance.
>>>>
>>>> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
>>>> ---
>>>>   mm/arch_pgtable_test.c | 3 +++
>>>>   1 file changed, 3 insertions(+)
>>>>
>>>> diff --git a/mm/arch_pgtable_test.c b/mm/arch_pgtable_test.c
>>>> index 8b4a92756ad8..f2b3c9ec35fa 100644
>>>> --- a/mm/arch_pgtable_test.c
>>>> +++ b/mm/arch_pgtable_test.c
>>>> @@ -24,6 +24,7 @@
>>>>   #include <linux/swap.h>
>>>>   #include <linux/swapops.h>
>>>>   #include <linux/sched/mm.h>
>>>> +#include <linux/highmem.h>
>>>
>>> This is okay.
>>>
>>>>   #include <asm/pgalloc.h>
>>>>   #include <asm/pgtable.h>
>>>> @@ -400,6 +401,8 @@ static int __init arch_pgtable_tests_init(void)
>>>>       p4d_clear_tests(p4dp);
>>>>       pgd_clear_tests(mm, pgdp);
>>>> +    pte_unmap(ptep);
>>>> +
>>>
>>> Now the preemption imbalance via pte_alloc_map() path i.e
>>>
>>> pte_alloc_map() -> pte_offset_map() -> kmap_atomic()
>>>
>>> Is not this very much powerpc 32 specific or this will be applicable
>>> for all platform which uses kmap_XXX() to map high memory ?
>>>
>>
>> See https://elixir.bootlin.com/linux/v5.3-rc8/source/include/linux/highmem.h#L91
>>
>> I think it applies at least to all arches using the generic implementation.
>>
>> Applies also to arm:
>> https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/arm/mm/highmem.c#L52
>>
>> Applies also to mips:
>> https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/mips/mm/highmem.c#L47
>>
>> Same on sparc:
>> https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/sparc/mm/highmem.c#L52
>>
>> Same on x86:
>> https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/x86/mm/highmem_32.c#L34
>>
>> I have not checked others, but I guess it is like that for all.
>>
> 
> 
> Seems like I answered too quickly. All kmap_atomic() do preempt_disable(), but not all pte_alloc_map() call kmap_atomic().
> 
> However, for instance ARM does:
> 
> https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/arm/include/asm/pgtable.h#L200
> 
> And X86 as well:
> 
> https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/x86/include/asm/pgtable_32.h#L51
> 
> Microblaze also:
> 
> https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/microblaze/include/asm/pgtable.h#L495

All the above platforms checks out to be using k[un]map_atomic(). I am wondering whether
any of the intermediate levels will have similar problems on any these 32 bit platforms
or any other platforms which might be using generic k[un]map_atomic(). There can be many
permutations here.

	p4dp = p4d_alloc(mm, pgdp, vaddr);
	pudp = pud_alloc(mm, p4dp, vaddr);
	pmdp = pmd_alloc(mm, pudp, vaddr);

Otherwise pte_alloc_map()/pte_unmap() looks good enough which will atleast take care of
a known failure.
Kirill A. Shutemov Sept. 13, 2019, 8:51 a.m. UTC | #5
On Fri, Sep 13, 2019 at 02:12:45PM +0530, Anshuman Khandual wrote:
> 
> 
> On 09/13/2019 12:41 PM, Christophe Leroy wrote:
> > 
> > 
> > Le 13/09/2019 à 09:03, Christophe Leroy a écrit :
> >>
> >>
> >> Le 13/09/2019 à 08:58, Anshuman Khandual a écrit :
> >>> On 09/13/2019 11:53 AM, Christophe Leroy wrote:
> >>>> Fix build failure on powerpc.
> >>>>
> >>>> Fix preemption imbalance.
> >>>>
> >>>> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> >>>> ---
> >>>>   mm/arch_pgtable_test.c | 3 +++
> >>>>   1 file changed, 3 insertions(+)
> >>>>
> >>>> diff --git a/mm/arch_pgtable_test.c b/mm/arch_pgtable_test.c
> >>>> index 8b4a92756ad8..f2b3c9ec35fa 100644
> >>>> --- a/mm/arch_pgtable_test.c
> >>>> +++ b/mm/arch_pgtable_test.c
> >>>> @@ -24,6 +24,7 @@
> >>>>   #include <linux/swap.h>
> >>>>   #include <linux/swapops.h>
> >>>>   #include <linux/sched/mm.h>
> >>>> +#include <linux/highmem.h>
> >>>
> >>> This is okay.
> >>>
> >>>>   #include <asm/pgalloc.h>
> >>>>   #include <asm/pgtable.h>
> >>>> @@ -400,6 +401,8 @@ static int __init arch_pgtable_tests_init(void)
> >>>>       p4d_clear_tests(p4dp);
> >>>>       pgd_clear_tests(mm, pgdp);
> >>>> +    pte_unmap(ptep);
> >>>> +
> >>>
> >>> Now the preemption imbalance via pte_alloc_map() path i.e
> >>>
> >>> pte_alloc_map() -> pte_offset_map() -> kmap_atomic()
> >>>
> >>> Is not this very much powerpc 32 specific or this will be applicable
> >>> for all platform which uses kmap_XXX() to map high memory ?
> >>>
> >>
> >> See https://elixir.bootlin.com/linux/v5.3-rc8/source/include/linux/highmem.h#L91
> >>
> >> I think it applies at least to all arches using the generic implementation.
> >>
> >> Applies also to arm:
> >> https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/arm/mm/highmem.c#L52
> >>
> >> Applies also to mips:
> >> https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/mips/mm/highmem.c#L47
> >>
> >> Same on sparc:
> >> https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/sparc/mm/highmem.c#L52
> >>
> >> Same on x86:
> >> https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/x86/mm/highmem_32.c#L34
> >>
> >> I have not checked others, but I guess it is like that for all.
> >>
> > 
> > 
> > Seems like I answered too quickly. All kmap_atomic() do preempt_disable(), but not all pte_alloc_map() call kmap_atomic().
> > 
> > However, for instance ARM does:
> > 
> > https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/arm/include/asm/pgtable.h#L200
> > 
> > And X86 as well:
> > 
> > https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/x86/include/asm/pgtable_32.h#L51
> > 
> > Microblaze also:
> > 
> > https://elixir.bootlin.com/linux/v5.3-rc8/source/arch/microblaze/include/asm/pgtable.h#L495
> 
> All the above platforms checks out to be using k[un]map_atomic(). I am wondering whether
> any of the intermediate levels will have similar problems on any these 32 bit platforms
> or any other platforms which might be using generic k[un]map_atomic().

No. Kernel only allocates pte page table from highmem. All other page
tables are always visible in kernel address space.
Anshuman Khandual Sept. 18, 2019, 7:32 a.m. UTC | #6
On 09/13/2019 11:53 AM, Christophe Leroy wrote:
> Fix build failure on powerpc.
> 
> Fix preemption imbalance.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> ---
>  mm/arch_pgtable_test.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/mm/arch_pgtable_test.c b/mm/arch_pgtable_test.c
> index 8b4a92756ad8..f2b3c9ec35fa 100644
> --- a/mm/arch_pgtable_test.c
> +++ b/mm/arch_pgtable_test.c
> @@ -24,6 +24,7 @@
>  #include <linux/swap.h>
>  #include <linux/swapops.h>
>  #include <linux/sched/mm.h>
> +#include <linux/highmem.h>
>  #include <asm/pgalloc.h>
>  #include <asm/pgtable.h>
>  
> @@ -400,6 +401,8 @@ static int __init arch_pgtable_tests_init(void)
>  	p4d_clear_tests(p4dp);
>  	pgd_clear_tests(mm, pgdp);
>  
> +	pte_unmap(ptep);
> +
>  	pmd_populate_tests(mm, pmdp, saved_ptep);
>  	pud_populate_tests(mm, pudp, saved_pmdp);
>  	p4d_populate_tests(mm, p4dp, saved_pudp);
> 

Hello Christophe,

I am planning to fold this fix into the current patch and retain your
Signed-off-by. Are you okay with it ?

- Anshuman
Christophe Leroy Sept. 19, 2019, 5:44 a.m. UTC | #7
Le 18/09/2019 à 09:32, Anshuman Khandual a écrit :
> 
> 
> On 09/13/2019 11:53 AM, Christophe Leroy wrote:
>> Fix build failure on powerpc.
>>
>> Fix preemption imbalance.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
>> ---
>>   mm/arch_pgtable_test.c | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/mm/arch_pgtable_test.c b/mm/arch_pgtable_test.c
>> index 8b4a92756ad8..f2b3c9ec35fa 100644
>> --- a/mm/arch_pgtable_test.c
>> +++ b/mm/arch_pgtable_test.c
>> @@ -24,6 +24,7 @@
>>   #include <linux/swap.h>
>>   #include <linux/swapops.h>
>>   #include <linux/sched/mm.h>
>> +#include <linux/highmem.h>
>>   #include <asm/pgalloc.h>
>>   #include <asm/pgtable.h>
>>   
>> @@ -400,6 +401,8 @@ static int __init arch_pgtable_tests_init(void)
>>   	p4d_clear_tests(p4dp);
>>   	pgd_clear_tests(mm, pgdp);
>>   
>> +	pte_unmap(ptep);
>> +
>>   	pmd_populate_tests(mm, pmdp, saved_ptep);
>>   	pud_populate_tests(mm, pudp, saved_pmdp);
>>   	p4d_populate_tests(mm, p4dp, saved_pudp);
>>
> 
> Hello Christophe,
> 
> I am planning to fold this fix into the current patch and retain your
> Signed-off-by. Are you okay with it ?
> 

No problem, do whatever is convenient for you. You can keep the 
signed-off-by, or use tested-by: as I tested it on PPC32.

Christophe

Patch
diff mbox series

diff --git a/mm/arch_pgtable_test.c b/mm/arch_pgtable_test.c
index 8b4a92756ad8..f2b3c9ec35fa 100644
--- a/mm/arch_pgtable_test.c
+++ b/mm/arch_pgtable_test.c
@@ -24,6 +24,7 @@ 
 #include <linux/swap.h>
 #include <linux/swapops.h>
 #include <linux/sched/mm.h>
+#include <linux/highmem.h>
 #include <asm/pgalloc.h>
 #include <asm/pgtable.h>
 
@@ -400,6 +401,8 @@  static int __init arch_pgtable_tests_init(void)
 	p4d_clear_tests(p4dp);
 	pgd_clear_tests(mm, pgdp);
 
+	pte_unmap(ptep);
+
 	pmd_populate_tests(mm, pmdp, saved_ptep);
 	pud_populate_tests(mm, pudp, saved_pmdp);
 	p4d_populate_tests(mm, p4dp, saved_pudp);