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* [PATCH v2] ARM: memblock limit must be pmd-aligned
@ 2017-06-27 17:33 Doug Berger
  2017-06-29 11:16 ` Mark Rutland
  0 siblings, 1 reply; 3+ messages in thread
From: Doug Berger @ 2017-06-27 17:33 UTC (permalink / raw)
  To: Russell King
  Cc: Doug Berger, Laura Abbott, Ard Biesheuvel, Nicolas Pitre,
	Jon Medhurst, Florian Fainelli, Kees Cook, Marc Zyngier,
	moderated list:ARM PORT, open list

The pmd containing memblock_limit is cleared by prepare_page_table()
which creates the opportunity for early_alloc() to allocate unmapped
memory if memblock_limit is not pmd aligned causing a boot-time hang.

Commit 965278dcb8ab ("ARM: 8356/1: mm: handle non-pmd-aligned end of RAM")
attempted to resolve this problem, but there is a path through the
adjust_lowmem_bounds() routine where if all memory regions start and
end on pmd-aligned addresses the memblock_limit will be set to
arm_lowmem_limit.

Since arm_lowmem_limit can be affected by the vmalloc early parameter,
the value of arm_lowmem_limit may not be pmd-aligned. This commit
corrects this oversight such that memblock_limit is always rounded
down to pmd-alignment.

Fixes: 965278dcb8ab ("ARM: 8356/1: mm: handle non-pmd-aligned end of RAM")
Signed-off-by: Doug Berger <opendmb@gmail.com>
Suggested-by: Mark Rutland <mark.rutland@arm.com>
---
Changes for v2:
 - Cleaner equivalent implementation suggested by Mark Rutland
 - Revised description to better capture the history

 arch/arm/mm/mmu.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 31af3cb59a60..e46a6a446cdd 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -1218,15 +1218,15 @@ void __init adjust_lowmem_bounds(void)
 
 	high_memory = __va(arm_lowmem_limit - 1) + 1;
 
+	if (!memblock_limit)
+		memblock_limit = arm_lowmem_limit;
+
 	/*
 	 * Round the memblock limit down to a pmd size.  This
 	 * helps to ensure that we will allocate memory from the
 	 * last full pmd, which should be mapped.
 	 */
-	if (memblock_limit)
-		memblock_limit = round_down(memblock_limit, PMD_SIZE);
-	if (!memblock_limit)
-		memblock_limit = arm_lowmem_limit;
+	memblock_limit = round_down(memblock_limit, PMD_SIZE);
 
 	if (!IS_ENABLED(CONFIG_HIGHMEM) || cache_is_vipt_aliasing()) {
 		if (memblock_end_of_DRAM() > arm_lowmem_limit) {
-- 
2.13.0

^ permalink raw reply related	[flat|nested] 3+ messages in thread
* Re: [PATCH v2] ARM: memblock limit must be pmd-aligned
  2017-06-27 17:33 [PATCH v2] ARM: memblock limit must be pmd-aligned Doug Berger
@ 2017-06-29 11:16 ` Mark Rutland
  2017-06-29 17:56   ` [PATCH] ARM: ensure memblock-limit is pmd-aligned Doug Berger
  0 siblings, 1 reply; 3+ messages in thread
From: Mark Rutland @ 2017-06-29 11:16 UTC (permalink / raw)
  To: Doug Berger
  Cc: Russell King, Nicolas Pitre, Jon Medhurst, Florian Fainelli,
	Kees Cook, Ard Biesheuvel, Marc Zyngier, open list, Laura Abbott,
	moderated list:ARM PORT

On Tue, Jun 27, 2017 at 10:33:29AM -0700, Doug Berger wrote:
> The pmd containing memblock_limit is cleared by prepare_page_table()
> which creates the opportunity for early_alloc() to allocate unmapped
> memory if memblock_limit is not pmd aligned causing a boot-time hang.
> 
> Commit 965278dcb8ab ("ARM: 8356/1: mm: handle non-pmd-aligned end of RAM")
> attempted to resolve this problem, but there is a path through the
> adjust_lowmem_bounds() routine where if all memory regions start and
> end on pmd-aligned addresses the memblock_limit will be set to
> arm_lowmem_limit.
> 
> Since arm_lowmem_limit can be affected by the vmalloc early parameter,
> the value of arm_lowmem_limit may not be pmd-aligned. This commit
> corrects this oversight such that memblock_limit is always rounded
> down to pmd-alignment.
> 
> Fixes: 965278dcb8ab ("ARM: 8356/1: mm: handle non-pmd-aligned end of RAM")
> Signed-off-by: Doug Berger <opendmb@gmail.com>
> Suggested-by: Mark Rutland <mark.rutland@arm.com>

As a minor nit, it would be better for the title to be something like
"ARM: ensure memblock-limit is pmd-aligned", but either way:

Acked-by: Mark Rutland <mark.rutland@arm.com>

Assuming Russell doesn't have any furhter comments, this looks good to
drop into the patch system. See:

  http://www.arm.linux.org.uk/developer/patches/info.php

... for instructions on how to send patches there.

Thanks,
Mark.

> ---
> Changes for v2:
>  - Cleaner equivalent implementation suggested by Mark Rutland
>  - Revised description to better capture the history
> 
>  arch/arm/mm/mmu.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> index 31af3cb59a60..e46a6a446cdd 100644
> --- a/arch/arm/mm/mmu.c
> +++ b/arch/arm/mm/mmu.c
> @@ -1218,15 +1218,15 @@ void __init adjust_lowmem_bounds(void)
>  
>  	high_memory = __va(arm_lowmem_limit - 1) + 1;
>  
> +	if (!memblock_limit)
> +		memblock_limit = arm_lowmem_limit;
> +
>  	/*
>  	 * Round the memblock limit down to a pmd size.  This
>  	 * helps to ensure that we will allocate memory from the
>  	 * last full pmd, which should be mapped.
>  	 */
> -	if (memblock_limit)
> -		memblock_limit = round_down(memblock_limit, PMD_SIZE);
> -	if (!memblock_limit)
> -		memblock_limit = arm_lowmem_limit;
> +	memblock_limit = round_down(memblock_limit, PMD_SIZE);
>  
>  	if (!IS_ENABLED(CONFIG_HIGHMEM) || cache_is_vipt_aliasing()) {
>  		if (memblock_end_of_DRAM() > arm_lowmem_limit) {
> -- 
> 2.13.0
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply	[flat|nested] 3+ messages in thread
* Re: [PATCH] ARM: ensure memblock-limit is pmd-aligned
  2017-06-29 11:16 ` Mark Rutland
@ 2017-06-29 17:56   ` Doug Berger
  0 siblings, 0 replies; 3+ messages in thread
From: Doug Berger @ 2017-06-29 17:56 UTC (permalink / raw)
  To: Mark Rutland
  Cc: Russell King, Nicolas Pitre, Jon Medhurst, Florian Fainelli,
	Kees Cook, Ard Biesheuvel, Marc Zyngier, open list, Laura Abbott,
	moderated list:ARM PORT

On 06/29/2017 04:16 AM, Mark Rutland wrote:
> On Tue, Jun 27, 2017 at 10:33:29AM -0700, Doug Berger wrote:
>> The pmd containing memblock_limit is cleared by prepare_page_table()
>> which creates the opportunity for early_alloc() to allocate unmapped
>> memory if memblock_limit is not pmd aligned causing a boot-time hang.
>>
>> Commit 965278dcb8ab ("ARM: 8356/1: mm: handle non-pmd-aligned end of RAM")
>> attempted to resolve this problem, but there is a path through the
>> adjust_lowmem_bounds() routine where if all memory regions start and
>> end on pmd-aligned addresses the memblock_limit will be set to
>> arm_lowmem_limit.
>>
>> Since arm_lowmem_limit can be affected by the vmalloc early parameter,
>> the value of arm_lowmem_limit may not be pmd-aligned. This commit
>> corrects this oversight such that memblock_limit is always rounded
>> down to pmd-alignment.
>>
>> Fixes: 965278dcb8ab ("ARM: 8356/1: mm: handle non-pmd-aligned end of RAM")
>> Signed-off-by: Doug Berger <opendmb@gmail.com>
>> Suggested-by: Mark Rutland <mark.rutland@arm.com>
> 
> As a minor nit, it would be better for the title to be something like
> "ARM: ensure memblock-limit is pmd-aligned", but either way:
> 
> Acked-by: Mark Rutland <mark.rutland@arm.com>
> 
> Assuming Russell doesn't have any furhter comments, this looks good to
> drop into the patch system. See:
> 
>   http://www.arm.linux.org.uk/developer/patches/info.php
> 
> ... for instructions on how to send patches there.
> 
> Thanks,
> Mark.
> 

I modified the title as suggested and it has been submitted as 8685/1.

Thanks!

>> ---
>> Changes for v2:
>>  - Cleaner equivalent implementation suggested by Mark Rutland
>>  - Revised description to better capture the history
>>
>>  arch/arm/mm/mmu.c | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
>> index 31af3cb59a60..e46a6a446cdd 100644
>> --- a/arch/arm/mm/mmu.c
>> +++ b/arch/arm/mm/mmu.c
>> @@ -1218,15 +1218,15 @@ void __init adjust_lowmem_bounds(void)
>>  
>>  	high_memory = __va(arm_lowmem_limit - 1) + 1;
>>  
>> +	if (!memblock_limit)
>> +		memblock_limit = arm_lowmem_limit;
>> +
>>  	/*
>>  	 * Round the memblock limit down to a pmd size.  This
>>  	 * helps to ensure that we will allocate memory from the
>>  	 * last full pmd, which should be mapped.
>>  	 */
>> -	if (memblock_limit)
>> -		memblock_limit = round_down(memblock_limit, PMD_SIZE);
>> -	if (!memblock_limit)
>> -		memblock_limit = arm_lowmem_limit;
>> +	memblock_limit = round_down(memblock_limit, PMD_SIZE);
>>  
>>  	if (!IS_ENABLED(CONFIG_HIGHMEM) || cache_is_vipt_aliasing()) {
>>  		if (memblock_end_of_DRAM() > arm_lowmem_limit) {
>> -- 
>> 2.13.0
>>
>>
>> _______________________________________________
>> linux-arm-kernel mailing list
>> linux-arm-kernel@lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply	[flat|nested] 3+ messages in thread
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2017-06-27 17:33 [PATCH v2] ARM: memblock limit must be pmd-aligned Doug Berger
2017-06-29 11:16 ` Mark Rutland
2017-06-29 17:56   ` [PATCH] ARM: ensure memblock-limit is pmd-aligned Doug Berger

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