[PATCH v1 10/11] blk-crypto: add slot_offset to blk_crypto_profile

[Linlin Zhang]

From: linlzhan <linlin.zhang@xxxxxxxxxxxxxxxx>

On platforms where ICE keyslots are partitioned across the host and
guest VMs, the host's physical keyslot range does not necessarily start
at slot 0.  blk_crypto_keyslot_index() currently returns a 0-based
array index, which is wrong for such configurations — hardware
programming requires the physical slot number, not the array position.

Add an unsigned int slot_offset field to struct blk_crypto_profile.
It defaults to zero (no change for existing drivers) and is set by
storage drivers that share ICE hardware across guests.

Update blk_crypto_keyslot_index() to add slot_offset to the array
index so that callers always receive the correct physical ICE keyslot
number to program into hardware.

Signed-off-by: linlzhan <linlin.zhang@xxxxxxxxxxxxxxxx>
---
 block/blk-crypto-profile.c         | 7 ++++---
 include/linux/blk-crypto-profile.h | 9 +++++++++
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/block/blk-crypto-profile.c b/block/blk-crypto-profile.c
index 53126c091b0b..64202d64a018 100644
--- a/block/blk-crypto-profile.c
+++ b/block/blk-crypto-profile.c
@@ -218,14 +218,15 @@ blk_crypto_find_and_grab_keyslot(struct blk_crypto_profile *profile,
 }
 
 /**
- * blk_crypto_keyslot_index() - Get the index of a keyslot
+ * blk_crypto_keyslot_index() - Get the physical index of a keyslot
  * @slot: a keyslot that blk_crypto_get_keyslot() returned
  *
- * Return: the 0-based index of the keyslot within the device's keyslots.
+ * Return: the physical ICE keyslot index, i.e. the 0-based position of @slot
+ * within the profile's keyslot array plus @slot->profile->slot_offset.
  */
 unsigned int blk_crypto_keyslot_index(struct blk_crypto_keyslot *slot)
 {
-	return slot - slot->profile->slots;
+	return (slot - slot->profile->slots) + slot->profile->slot_offset;
 }
 EXPORT_SYMBOL_GPL(blk_crypto_keyslot_index);
 
diff --git a/include/linux/blk-crypto-profile.h b/include/linux/blk-crypto-profile.h
index 4f39e9cd7576..a9bdc05abfa3 100644
--- a/include/linux/blk-crypto-profile.h
+++ b/include/linux/blk-crypto-profile.h
@@ -162,6 +162,15 @@ struct blk_crypto_profile {
 	 */
 	struct device *dev;
 
+	/**
+	 * @slot_offset: offset added to the slot array index to obtain the
+	 * physical ICE keyslot number.  Zero in the common case.  Set to a
+	 * non-zero value by storage drivers that share ICE hardware across
+	 * multiple guests, where the host's keyslots do not start at physical
+	 * slot 0.
+	 */
+	unsigned int slot_offset;
+
 	/* private: The following fields shouldn't be accessed by drivers. */
 
 	/* Number of keyslots, or 0 if not applicable */
-- 
2.34.1