ARM: mm: Fix the memblock allocation for LPAE machines

Commit ad6492b8 added much needed memblock_virt_alloc_low() and further
commit 07bacb3 {memblock, bootmem: restore goal for alloc_low} fixed the
issue with low memory limit thansk to Yinghai. But even after all these fixes,
there is still one case where the limit check done with ARCH_LOW_ADDRESS_LIMIT
for low memory fails. Russell pointed out the issue with 32 bit LPAE machines
in below thread.
	https://lkml.org/lkml/2014/1/28/364

Since on some LPAE machines where memory start address is beyond 4GB,
the low memory marker in memblock will be set to default
ARCH_LOW_ADDRESS_LIMIT which is wrong. We can fix this by letting
architectures set the ARCH_LOW_ADDRESS_LIMIT using another export
similar to memblock_set_current_limit() but am not sure whether
its worth the trouble. Tell me if you think otherwise.

Rather am just trying to fix that one broken case using memblock_virt_alloc()
in setup code since the memblock.current_limit is updated appropriately
makes it work on all ARM 32 bit machines.

Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Strashko, Grygorii <grygorii.strashko@ti.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
---
 arch/arm/kernel/setup.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Russell,

On Saturday 01 February 2014 03:14 PM, Santosh Shilimkar wrote:
> Commit ad6492b8 added much needed memblock_virt_alloc_low() and further
> commit 07bacb3 {memblock, bootmem: restore goal for alloc_low} fixed the
> issue with low memory limit thansk to Yinghai. But even after all these fixes,
> there is still one case where the limit check done with ARCH_LOW_ADDRESS_LIMIT
> for low memory fails. Russell pointed out the issue with 32 bit LPAE machines
> in below thread.
> 	https://lkml.org/lkml/2014/1/28/364
> 
> Since on some LPAE machines where memory start address is beyond 4GB,
> the low memory marker in memblock will be set to default
> ARCH_LOW_ADDRESS_LIMIT which is wrong. We can fix this by letting
> architectures set the ARCH_LOW_ADDRESS_LIMIT using another export
> similar to memblock_set_current_limit() but am not sure whether
> its worth the trouble. Tell me if you think otherwise.
> 
> Rather am just trying to fix that one broken case using memblock_virt_alloc()
> in setup code since the memblock.current_limit is updated appropriately
> makes it work on all ARM 32 bit machines.
> 
> Cc: Yinghai Lu <yinghai@kernel.org>
> Cc: Russell King <linux@arm.linux.org.uk>
> Cc: Strashko, Grygorii <grygorii.strashko@ti.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
> ---
Whats you say here ? We should get the fix for the
issue. If you are ok, I can drop the patch in patch system.

>  arch/arm/kernel/setup.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
> index b0df976..1e8b030 100644
> --- a/arch/arm/kernel/setup.c
> +++ b/arch/arm/kernel/setup.c
> @@ -731,7 +731,7 @@ static void __init request_standard_resources(const struct machine_desc *mdesc)
>  	kernel_data.end     = virt_to_phys(_end - 1);
>  
>  	for_each_memblock(memory, region) {
> -		res = memblock_virt_alloc_low(sizeof(*res), 0);
> +		res = memblock_virt_alloc(sizeof(*res), 0);
>  		res->name  = "System RAM";
>  		res->start = __pfn_to_phys(memblock_region_memory_base_pfn(region));
>  		res->end = __pfn_to_phys(memblock_region_memory_end_pfn(region)) - 1;
> 

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On Wednesday 05 February 2014 06:48 PM, Russell King - ARM Linux wrote:
> On Wed, Feb 05, 2014 at 06:39:44PM -0500, Santosh Shilimkar wrote:
>> Russell,
>>
>> On Saturday 01 February 2014 03:14 PM, Santosh Shilimkar wrote:
>>> Commit ad6492b8 added much needed memblock_virt_alloc_low() and further
>>> commit 07bacb3 {memblock, bootmem: restore goal for alloc_low} fixed the
>>> issue with low memory limit thansk to Yinghai. But even after all these fixes,
>>> there is still one case where the limit check done with ARCH_LOW_ADDRESS_LIMIT
>>> for low memory fails. Russell pointed out the issue with 32 bit LPAE machines
>>> in below thread.
>>> 	https://lkml.org/lkml/2014/1/28/364
>>>
>>> Since on some LPAE machines where memory start address is beyond 4GB,
>>> the low memory marker in memblock will be set to default
>>> ARCH_LOW_ADDRESS_LIMIT which is wrong. We can fix this by letting
>>> architectures set the ARCH_LOW_ADDRESS_LIMIT using another export
>>> similar to memblock_set_current_limit() but am not sure whether
>>> its worth the trouble. Tell me if you think otherwise.
>>>
>>> Rather am just trying to fix that one broken case using memblock_virt_alloc()
>>> in setup code since the memblock.current_limit is updated appropriately
>>> makes it work on all ARM 32 bit machines.
>>>
>>> Cc: Yinghai Lu <yinghai@kernel.org>
>>> Cc: Russell King <linux@arm.linux.org.uk>
>>> Cc: Strashko, Grygorii <grygorii.strashko@ti.com>
>>> Cc: Andrew Morton <akpm@linux-foundation.org>
>>> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
>>> ---
>> Whats you say here ? We should get the fix for the
>> issue. If you are ok, I can drop the patch in patch system.
> 
> Is this still an issue, or has Tejun fixed it by some other means?  I've not
> noticed anything being broken at the moment.
> 
> Can you confirm whether we still have an issue without this patch please?
> 
Fixes for all cases exist except 'LPAE + memory start beyond 4 GB'.
This case is still broken and  hence I posted the $subject patch.

Regards,
Santosh

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