x86/fred: Fix system hang during S4 resume with FRED enabled

Upon a wakeup from S4, the restore kernel starts and initializes the
FRED MSRs as needed from its perspective.  It then loads a hibernation
image, including the image kernel, and attempts to load image pages
directly into their original page frames used before hibernation unless
those frames are currently in use.  Once all pages are moved to their
original locations, it jumps to a "trampoline" page in the image kernel.

At this point, the image kernel takes control, but the FRED MSRs still
contain values set by the restore kernel, which may differ from those
set by the image kernel before hibernation.  Therefore, the image kernel
must ensure the FRED MSRs have the same values as before hibernation.
Since these values depend only on the location of the kernel text and
data, they can be recomputed from scratch.

Reported-by: Xi Pardee <xi.pardee@intel.com>
Reported-by: Todd Brandt <todd.e.brandt@intel.com>
Tested-by: Todd Brandt <todd.e.brandt@intel.com>
Suggested-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Xin Li (Intel) <xin@zytor.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250401075728.3626147-1-xin@zytor.com

0 files changed, 0 insertions, 0 deletions