Re: [linux-pm] Re: [patch] hibernation: utilize ACPI hardware signature

[Nigel Cunningham <nigel@nigel.suspend2.net>]

Hi.

Rafael J. Wysocki wrote:
> On Wednesday, 2 of January 2008, Shaohua Li wrote:
>> ACPI defines a hardware signature. BIOS calculates the signature
>> according to hardware configure, if hardware changes, the signature will
>> change, in this case, S4 resume should fail.
> 
> The idea is fine, but I'd prefer to do that in a more straightforward way.
> Namely, we can just:
> * write the signature into a variable in, for example,
>   acpi_hibernation_prepare() (then, the "old" signature value will be
>   automatically saved in the image)
> * compare it with a the "new" value read from the BIOS in
>   acpi_hibernation_leave() and panic if there's a mismatch
> * add a configuration option to disable this behavior (just in case)
> This way we can avoid modifying the entire generic interface to add the feature
> specific to ACPI.
> 
> Still, if you want the boot kernel to check the signature, which will be more
> elegant (but please note that on x86-64 the boot kernel need not support ACPI
> at all), you can use the (recently introduced) architecture part of the image
> header for this purpose, without modifying the generic interface.

I suppose we can always disable this when we start to support hardware
changing over hibernate (I have ideas in this direction - memory cold
plugging, for a start).

Regards,

Nigel