Re: [PATCH] check that acpi_wakeup_address is below 1MB v2

[matthieu castet <castet.matthieu@free.fr>]

Hi,

Rafael J. Wysocki wrote:
> On Friday, 11 of April 2008, Zhao Yakui wrote:
>> On Thu, 2008-04-10 at 23:33 +0200, matthieu castet wrote:
>>> Hi,
>>>
>>> this patch add a check that the memory allocated for s3 wakeup is in the 
>>> first 1MB as required by acpi spec.
>>>
>> Have you found whether some systems are afflicted by this ?
>>
>> In fact that OS allacates the acpi_wake_address follows the below two
>> functions:
>> reserve_bootmem(0, PAGE_SIZE, BOOTMEM_DEFAULT);
>> reserve_bootmem(PAGE_SIZE, PAGE_SIZE, BOOTMEM_DEFAULT);
>>
That's on 32 bits kernel. Aren't the 1MB limitation valid on 64 bits 
kernel ?

>> The above mechanism can insure that the acpi_wake_address is in memroy
>> below 1M. (It is unncessary to apply the patch. IMO)
> 
> Agreed.
>  
>> Of course the addressing check will be more strict after this patch is
>> applied.
> 
> Matthieu, can you please explain why you consider the patch as necessary?
This can help to debug strange S3 wakeup problem. It make sure the 
allocation is correct.

Also I believe relying on the bootmem allocator internal to be sure it 
is in the first 1MB is a bad things (why can't it start allocating 
memory to the top of 16MB memory).
If you are sure of the allocated memory before the call, why don't do a
reserve_bootmem(PAGE_SIZE*2, PAGE_SIZE*2, BOOTMEM_DEFAULT); ?


Matthieu