Re: Re: [patch] hibernation: utilize ACPI hardware signature

On Wednesday, 2 of January 2008, Nigel Cunningham wrote:

Hi.

Rafael J. Wysocki wrote:

quoted

On Wednesday, 2 of January 2008, Shaohua Li wrote:

quoted

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).

Well, if we support such features, we won't be following ACPI any more.

Greetings,
Rafael