[v5] PM / hibernate: Print the possible panic reason when resuming with inconsistent e820 map

On some platforms, there is occasional panic triggered when trying to
resume from hibernation, a typical panic looks like:

"BUG: unable to handle kernel paging request at ffff880085894000
IP: [<ffffffff810c5dc2>] load_image_lzo+0x8c2/0xe70"

This is because e820 map has been changed by BIOS before/after
hibernation, and one of the page frames from first kernel
is right located in second kernel's unmapped region, so panic
comes out when accessing unmapped kernel address.

In order to tell user why this happeneded, and for scalability,
we introduce a framework to compare the e820 maps before/after
hibernation. If these two e820 maps are not compatible with
each other, we will print the first corrupt e820 entry's information
(there might be more than one broken e820 entries) once system
goes into panic, for example:

BUG: unable to handle kernel paging request at ffff8800a9688000
IP: [<ffffffff810c5dc2>] load_image_lzo+0x8c2/0xe70
PM: Hibernation Caution! Oops might be due to inconsistent e820 table.
PM: mem [0xa963b000-0xa963d000][ACPI Table] is an invalid old e820 region.
PM: Inconsistent with current [mem 0xa963b000-0xa963e000][ACPI Table].
PM: Please update your BIOS, or do not use hibernation on this machine.

The following e820 entries will be regarded as invalid ones:
1.E820_RAM:  old region is not a subset of any current region.
2.E820_ACPI: old region is not strictly the same as any current
             region(example above).

Signed-off-by: Chen Yu <yu.c.chen@intel.com>
---
v5:
 - Rewrite this patch to just warn user of the broken BIOS
   when panic.
v4:
 - Add __attribute__ ((unused)) for swsusp_page_is_valid,
   to eliminate the warnning of:
   'swsusp_page_is_valid' defined but not used
   on non-x86 platforms.

v3:
 - Adjust the logic to exclude the end_pfn boundary in pfn_mapped
   when invoking mark_valid_pages, because the end_pfn is not
   a mapped page frame, we should not regard it as a valid page.

   Move the sanity check of valid pages to a early stage in resuming
   process(moved to mark_unsafe_pages), in this way, we can avoid
   unnecessarily accessing these invalid pages in later stage(yes,
   move to the original position Joey once introduced in:
   Commit 84c91b7ae07c ("PM / hibernate: avoid unsafe pages in e820
   reserved regions")

   With v3 patch applied, I did 30 cycles on my problematic platform,
   no panic triggered anymore(50% reproducible before patched, by
   plugging/unplugging memory peripheral during hibernation), and it
   just warns of invalid pages.

v2:
 - According to Ingo's suggestion, rewrite this patch.

   New version just checks each page frame according to pfn_mapped array.
   So that we do not need to touch existing code related to
   E820_RESERVED_KERN. And this method can naturely guarantee
   that the system before/after hibernation do not need to be of
   the same memory size on x86_64.
---
 arch/x86/Kconfig               |   4 +
 arch/x86/include/asm/suspend.h |   3 +
 arch/x86/power/Makefile        |   2 +-
 arch/x86/power/hibernate.c     | 229 +++++++++++++++++++++++++++++++++++++++++
 include/linux/suspend.h        |  16 +++
 kernel/power/power.h           |   8 ++
 kernel/power/snapshot.c        |   8 ++
 7 files changed, 269 insertions(+), 1 deletion(-)
 create mode 100644 arch/x86/power/hibernate.c

[v5] PM / hibernate: Print the possible panic reason when resuming with inconsistent e820 map

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