[PATCH] x86: Preserve ACPI memory area during hibernation

["Amadeusz Sławiński" <amadeuszx.slawinski@linux.intel.com>]

When overriding NHLT ACPI-table tests show that on some platforms
there is problem that NHLT contains garbage after hibernation/resume
cycle.

Problem stems from the fact that ACPI override performs early memory
allocation using memblock_phys_alloc_range() in
memblock_phys_alloc_range(). This memory block is later being marked as
ACPI memory block in arch_reserve_mem_area(). Later when memory areas
are considered for hibernation it is being marked as nosave in
e820__register_nosave_regions().

Fix this by skipping ACPI memory area altogether when considering areas
to mark as nosave.

Signed-off-by: Amadeusz Sławiński <amadeuszx.slawinski@linux.intel.com>
Reviewed-by: Cezary Rojewski <cezary.rojewski@intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 arch/x86/kernel/e820.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index bc0657f0deed..88c1b785ffe4 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -758,6 +758,18 @@ void __init e820__register_nosave_regions(unsigned long limit_pfn)
 	for (i = 0; i < e820_table->nr_entries; i++) {
 		struct e820_entry *entry = &e820_table->entries[i];
 
+		/*
+		 * Areas containing ACPI tables should be preserved during
+		 * hibernation to prevent potential problems caused by BIOS
+		 * upgrades when offline, as well as to preserve initrd
+		 * ACPI tables overrides which are applied on boot.
+		 * See also acpi_table_upgrade() & arch_reserve_mem_area()
+		 */
+		if (entry->type == E820_TYPE_ACPI) {
+			pfn = PFN_UP(entry->addr + entry->size);
+			continue;
+		}
+
 		if (pfn < PFN_UP(entry->addr))
 			register_nosave_region(pfn, PFN_UP(entry->addr));
 
-- 
2.25.1