ide: preserve Host Protected Area by default (v2)

From the perspective of most users of recent systems, disabling Host
Protected Area (HPA) can break vendor RAID formats, GPT partitions and
risks corrupting firmware or overwriting vendor system recovery tools.

Unfortunately the original (kernels < 2.6.30) behavior (unconditionally
disabling HPA and using full disk capacity) was introduced at the time
when the main use of HPA was to make the drive look small enough for the
BIOS to allow the system to boot with large capacity drives.

Thus to allow the maximum compatibility with the existing setups (using
HPA and partitioned with HPA disabled) we automically disable HPA if
any partitions overlapping HPA are detected.  Additionally HPA can also
be disabled using the "nohpa" module parameter (i.e. "ide_core.nohpa=0.0"
to disable HPA on /dev/hda).

v2:
Fix ->resume HPA support.

While at it:
- remove stale "idebus=" entry from Documentation/kernel-parameters.txt

Cc: Robert Hancock <hancockrwd@gmail.com>
Cc: Frans Pop <elendil@planet.nl>
Cc: "Andries E. Brouwer" <Andries.Brouwer@cwi.nl>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
[patch description was based on input from Alan Cox and Frans Pop]
Emphatically-Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

Documentation/ide/ide.txt

@@ -216,6 +216,8 @@ Other kernel parameters for ide_core are:
 
 * "noflush=[interface_number.device_number]" to disable flush requests
 
+* "nohpa=[interface_number.device_number]" to disable Host Protected Area
+
 * "noprobe=[interface_number.device_number]" to skip probing
 
 * "nowerr=[interface_number.device_number]" to ignore the WRERR_STAT bit

Documentation/kernel-parameters.txt

@@ -835,11 +835,8 @@ and is between 256 and 4096 characters. It is defined in the file
 
 	ide-core.nodma=	[HW] (E)IDE subsystem
 			Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
-			.vlb_clock .pci_clock .noflush .noprobe .nowerr .cdrom
-			.chs .ignore_cable are additional options
-			See Documentation/ide/ide.txt.
-
-	idebus=		[HW] (E)IDE subsystem - VLB/PCI bus speed
+			.vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
+			.cdrom .chs .ignore_cable are additional options
 			See Documentation/ide/ide.txt.
 
 	ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem

drivers/ide/ide-disk.c

@@ -350,6 +350,9 @@ static void idedisk_check_hpa(ide_drive_t *drive)
 			 capacity, sectors_to_MB(capacity),
 			 set_max, sectors_to_MB(set_max));
 
+	if ((drive->dev_flags & IDE_DFLAG_NOHPA) == 0)
+		return;
+
 	set_max = ide_disk_hpa_set_capacity(drive, set_max, lba48);
 	if (set_max)
 		printk(KERN_INFO "%s: Host Protected Area disabled.\n",
@@ -430,8 +433,11 @@ static u64 ide_disk_set_capacity(ide_drive_t *drive, u64 capacity)
 		goto out;
 
 	set = ide_disk_hpa_set_capacity(drive, set, lba48);
-	if (set)
+	if (set) {
+		/* needed for ->resume to disable HPA */
+		drive->dev_flags |= IDE_DFLAG_NOHPA;
 		return set;
+	}
 out:
 	return drive->capacity64;
 }

drivers/ide/ide.c

@@ -211,6 +211,11 @@ static unsigned int ide_noflush;
 module_param_call(noflush, ide_set_dev_param_mask, NULL, &ide_noflush, 0);
 MODULE_PARM_DESC(noflush, "disable flush requests for a device");
 
+static unsigned int ide_nohpa;
+
+module_param_call(nohpa, ide_set_dev_param_mask, NULL, &ide_nohpa, 0);
+MODULE_PARM_DESC(nohpa, "disable Host Protected Area for a device");
+
 static unsigned int ide_noprobe;
 
 module_param_call(noprobe, ide_set_dev_param_mask, NULL, &ide_noprobe, 0);
@@ -281,6 +286,11 @@ static void ide_dev_apply_params(ide_drive_t *drive, u8 unit)
 				 drive->name);
 		drive->dev_flags |= IDE_DFLAG_NOFLUSH;
 	}
+	if (ide_nohpa & (1 << i)) {
+		printk(KERN_INFO "ide: disabling Host Protected Area for %s\n",
+				 drive->name);
+		drive->dev_flags |= IDE_DFLAG_NOHPA;
+	}
 	if (ide_noprobe & (1 << i)) {
 		printk(KERN_INFO "ide: skipping probe for %s\n", drive->name);
 		drive->dev_flags |= IDE_DFLAG_NOPROBE;

include/linux/ide.h

@@ -475,6 +475,8 @@ enum {
 	IDE_DFLAG_NICE1			= (1 << 5),
 	/* device is physically present */
 	IDE_DFLAG_PRESENT		= (1 << 6),
+	/* disable Host Protected Area */
+	IDE_DFLAG_NOHPA			= (1 << 7),
 	/* id read from device (synthetic if not set) */
 	IDE_DFLAG_ID_READ		= (1 << 8),
 	IDE_DFLAG_NOPROBE		= (1 << 9),