Subject: ACPI: Implement overriding of arbitrary ACPI tables via initrd
From: Thomas Renninger <trenn@suse.de>
References: none
Patch-Mainline: submitted, aiming for 3.2

Details can be found in:
Documentation/acpi/initrd_table_override.txt

Additional dmesg output of a booted system with
FACP (FADT), DSDT and SSDT (the 9th dynamically loaded one)
tables overridden (with ### marked comments):

### ACPI tables found glued to initrd
DSDT ACPI table found in initrd - size: 16234
FACP ACPI table found in initrd - size: 116
SSDT ACPI table found in initrd - size: 334
### Re-printed e820 map via e820_update() with additionally created
### ACPI data section at 0xcff55000 where the ACPI tables passed via
### initrd where copied to
modified physical RAM map:
...
  ### New ACPI data section:
  modified: 00000000cff55000 - 00000000cff5912c (ACPI data)
  ### BIOS e820 provided ACPI data section:
  modified: 00000000cff60000 - 00000000cff69000 (ACPI data)
...
### Total size of all ACPI tables glued to initrd
### The address is initrd_start which gets updated to
### initrd_start = initrd_start + "size of all ACPI tables glued to initrd"
Found acpi tables of size: 16684 at 0xffff8800374c4000

Disabling lock debugging due to kernel taint
### initrd provided FACP and DSDT tables are used instead of BIOS provided ones
ACPI: FACP @ 0x00000000cff68dd8 Phys table override, replaced with:
ACPI: FACP 00000000cff58f6a 00074 (v01 INTEL  TUMWATER 06040000 PTL  00000003)
ACPI: DSDT @ 0x00000000cff649d4 Phys table override, replaced with:
ACPI: DSDT 00000000cff55000 04404 (v01  Intel BLAKFORD 06040000 MSFT 0100000E)
...
### Much later, the 9th (/sys/firmware/acpi/table/dynamic/SSDT9) dynamically
### loaded ACPI table matches and gets overridden:
ACPI: SSDT @ 0x00000000cff64824 Phys table override, replaced with:
ACPI: SSDT 00000000cff58fde 0014E (v01  PmRef  Cpu7Ist 00003000 INTL 20110316)
ACPI: Dynamic OEM Table Load:
ACPI: SSDT           (null) 0014E (v01  PmRef  Cpu7Ist 00003000 INTL 20110316)
...

If the initrd does not start with a valid ACPI table signature or the ACPI
table's checksum is wrong, there is no functional change.

Signed-off-by: Thomas Renninger <trenn@suse.de>
CC: linux-acpi@vger.kernel.org
CC: lenb@kernel.org
CC: linux-kernel@vger.kernel.org
CC: x86@kernel.org
Automatically created from "patches.arch/acpi_implement_overriding_of_arbitrary_acpi_tables_via_initrd.patch" by xen-port-patches.py

--- head.orig/arch/x86/kernel/setup-xen.c	2012-04-11 13:26:23.000000000 +0200
+++ head/arch/x86/kernel/setup-xen.c	2012-04-11 16:58:35.000000000 +0200
@@ -467,12 +467,20 @@ static void __init reserve_initrd(void)
 #ifdef CONFIG_X86_64_XEN
 		initrd_below_start_ok = 1;
 #endif
-		return;
+	} else {
+		relocate_initrd();
+		memblock_free(ramdisk_image, ramdisk_end - ramdisk_image);
 	}
-
-	relocate_initrd();
-
-	memblock_free(ramdisk_image, ramdisk_end - ramdisk_image);
+#ifdef CONFIG_ACPI_INITRD_TABLE_OVERRIDE
+	acpi_initrd_offset = acpi_initrd_table_override((void *)initrd_start,
+							(void *)initrd_end);
+	if (!acpi_initrd_offset)
+		return;
+	printk(KERN_INFO "Found acpi tables of size: %lu at 0x%lx\n",
+	       acpi_initrd_offset, initrd_start);
+	initrd_start += acpi_initrd_offset;
+	return;
+#endif
 }
 #else
 static void __init reserve_initrd(void)
--- head.orig/arch/x86/mm/init-xen.c	2012-04-11 13:26:23.000000000 +0200
+++ head/arch/x86/mm/init-xen.c	2012-04-11 16:58:44.000000000 +0200
@@ -464,6 +464,12 @@ void free_initrd_mem(unsigned long start
 	 *   - relocate_initrd()
 	 * So here We can do PAGE_ALIGN() safely to get partial page to be freed
 	 */
+#ifdef CONFIG_ACPI_INITRD_TABLE_OVERRIDE
+	if (acpi_initrd_offset)
+		free_init_pages("initrd memory", start - acpi_initrd_offset,
+				PAGE_ALIGN(end));
+	else
+#endif
 	free_init_pages("initrd memory", start, PAGE_ALIGN(end));
 }
 #endif