linux-kernel - [PATCH -mm] i386: Do not restore reserved memory after hibernation

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Date:	Sun, 3 Jun 2007 00:14:25 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Andrey Borzenkov <arvidjaar@...l.ru>,
	Nigel Cunningham <nigel@...el.suspend2.net>,
	Pavel Machek <pavel@....cz>, Andi Kleen <ak@...e.de>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH -mm] i386: Do not restore reserved memory after hibernation

[Not urgent, needs to be tested in -mm]
---
From: Rafael J. Wysocki <rjw@...k.pl>

On some systems the ACPI NVS area is located in the first 1 MB of RAM and
it is overwritten by the i386 code during the restore after hibernation.
This confuses the ACPI platform firmware that doesn't update the AC adapter
status appropriately as a result
(http://bugzilla.kernel.org/show_bug.cgi?id=7995).

The solution is to register the reserved memory in the first 1 MB as 'nosave',
so that swsusp doesn't touch it during the restore.  Also, this has been done
on x86_64 for a long time now, so this patch makes the i386 restore code behave
like the x86_64 one.

Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
Acked-by: Pavel Machek <pavel@....cz>
---
 arch/i386/kernel/e820.c  |   30 ++++++++++++++++++++++++++++++
 arch/i386/kernel/setup.c |    1 +
 include/asm-i386/e820.h  |    1 +
 3 files changed, 32 insertions(+)

Index: linux-2.6.22-rc3/arch/i386/kernel/e820.c
===================================================================
--- linux-2.6.22-rc3.orig/arch/i386/kernel/e820.c
+++ linux-2.6.22-rc3/arch/i386/kernel/e820.c
@@ -10,6 +10,7 @@
 #include <linux/efi.h>
 #include <linux/pfn.h>
 #include <linux/uaccess.h>
+#include <linux/suspend.h>
 
 #include <asm/pgtable.h>
 #include <asm/page.h>
@@ -320,6 +321,35 @@ static int __init request_standard_resou
 
 subsys_initcall(request_standard_resources);
 
+/**
+ * e820_mark_nosave_regions - Find the ranges of physical addresses that do not
+ * correspond to e820 RAM areas and mark the corresponding pages as nosave for
+ * hibernation.
+ *
+ * This function requires the e820 map to be sorted and without any
+ * overlapping entries and assumes the first e820 area to be RAM.
+ */
+void __init e820_mark_nosave_regions(void)
+{
+	int i;
+	unsigned long pfn;
+
+	pfn = PFN_DOWN(e820.map[0].addr + e820.map[0].size);
+	for (i = 1; i < e820.nr_map; i++) {
+		struct e820entry *ei = &e820.map[i];
+
+		if (pfn < PFN_UP(ei->addr))
+			register_nosave_region(pfn, PFN_UP(ei->addr));
+
+		pfn = PFN_DOWN(ei->addr + ei->size);
+		if (ei->type != E820_RAM)
+			register_nosave_region(PFN_UP(ei->addr), pfn);
+
+		if (pfn >= max_low_pfn)
+			break;
+	}
+}
+
 void __init add_memory_region(unsigned long long start,
 			      unsigned long long size, int type)
 {
Index: linux-2.6.22-rc3/arch/i386/kernel/setup.c
===================================================================
--- linux-2.6.22-rc3.orig/arch/i386/kernel/setup.c
+++ linux-2.6.22-rc3/arch/i386/kernel/setup.c
@@ -648,6 +648,7 @@ void __init setup_arch(char **cmdline_p)
 #endif
 
 	e820_register_memory();
+	e820_mark_nosave_regions();
 
 #ifdef CONFIG_VT
 #if defined(CONFIG_VGA_CONSOLE)
Index: linux-2.6.22-rc3/include/asm-i386/e820.h
===================================================================
--- linux-2.6.22-rc3.orig/include/asm-i386/e820.h
+++ linux-2.6.22-rc3/include/asm-i386/e820.h
@@ -44,6 +44,7 @@ extern void register_bootmem_low_pages(u
 extern void e820_register_memory(void);
 extern void limit_regions(unsigned long long size);
 extern void print_memory_map(char *who);
+extern void e820_mark_nosave_regions(void);
 
 #endif/*!__ASSEMBLY__*/
 
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