linux/arch/x86/kernel/acpi
David Woodhouse 74d9555580 PM: hibernate: Allow ACPI hardware signature to be honoured
Theoretically, when the hardware signature in FACS changes, the OS
is supposed to gracefully decline to attempt to resume from S4:

 "If the signature has changed, OSPM will not restore the system
  context and can boot from scratch"

In practice, Windows doesn't do this and many laptop vendors do allow
the signature to change especially when docking/undocking, so it would
be a bad idea to simply comply with the specification by default in the
general case.

However, there are use cases where we do want the compliant behaviour
and we know it's safe. Specifically, when resuming virtual machines where
we know the hypervisor has changed sufficiently that resume will fail.
We really want to be able to *tell* the guest kernel not to try, so it
boots cleanly and doesn't just crash. This patch provides a way to opt
in to the spec-compliant behaviour on the command line.

A follow-up patch may do this automatically for certain "known good"
machines based on a DMI match, or perhaps just for all hypervisor
guests since there's no good reason a hypervisor would change the
hardware_signature that it exposes to guests *unless* it wants them
to obey the ACPI specification.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2021-12-08 16:06:10 +01:00
..
apei.c x86/mce, cper: Pass x86 CPER through the MCA handling chain 2020-11-21 12:05:41 +01:00
boot.c x86/ACPI: Don't add CPUs that are not online capable 2021-09-13 19:19:02 +02:00
cppc_msr.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 288 2019-06-05 17:36:37 +02:00
cstate.c x86: ACPI: cstate: Optimize C3 entry on AMD CPUs 2021-10-01 20:44:31 +02:00
Makefile x86/acpi: Support objtool validation in wakeup_64.S 2021-01-26 11:33:03 -06:00
sleep.c PM: hibernate: Allow ACPI hardware signature to be honoured 2021-12-08 16:06:10 +01:00
sleep.h x86/acpi: make "asmlinkage" part first thing in the function definition 2020-03-14 10:29:07 +01:00
wakeup_32.S x86/asm/32: Add ENDs to some functions and relabel with SYM_CODE_* 2019-10-18 11:58:33 +02:00
wakeup_64.S kasan: remove redundant config option 2021-04-16 16:10:36 -07:00