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>

1 files changed, 7 insertions, 1 deletions

diff --git a/drivers/ide/ide-disk.c b/drivers/ide/ide-disk.c
index 61a6d35..3d92c9d 100644
--- a/drivers/ide/ide-disk.c
+++ b/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;
 }