diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index f09cc992af..46b0854d7e 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -463,8 +463,8 @@ static int coroutine_fn do_perform_cow_read(BlockDriverState *bs,
 }
 
 static bool coroutine_fn do_perform_cow_encrypt(BlockDriverState *bs,
-                                                uint64_t src_cluster_offset,
-                                                uint64_t cluster_offset,
+                                                uint64_t guest_cluster_offset,
+                                                uint64_t host_cluster_offset,
                                                 unsigned offset_in_cluster,
                                                 uint8_t *buffer,
                                                 unsigned bytes)
@@ -474,8 +474,9 @@ static bool coroutine_fn do_perform_cow_encrypt(BlockDriverState *bs,
         assert((offset_in_cluster & ~BDRV_SECTOR_MASK) == 0);
         assert((bytes & ~BDRV_SECTOR_MASK) == 0);
         assert(s->crypto);
-        if (qcow2_co_encrypt(bs, cluster_offset,
-                             src_cluster_offset + offset_in_cluster,
+        if (qcow2_co_encrypt(bs,
+                             host_cluster_offset + offset_in_cluster,
+                             guest_cluster_offset + offset_in_cluster,
                              buffer, bytes) < 0) {
             return false;
         }
diff --git a/block/qcow2-threads.c b/block/qcow2-threads.c
index 3b1e63fe41..9646243a9b 100644
--- a/block/qcow2-threads.c
+++ b/block/qcow2-threads.c
@@ -234,15 +234,15 @@ static int qcow2_encdec_pool_func(void *opaque)
 }
 
 static int coroutine_fn
-qcow2_co_encdec(BlockDriverState *bs, uint64_t file_cluster_offset,
-                  uint64_t offset, void *buf, size_t len, Qcow2EncDecFunc func)
+qcow2_co_encdec(BlockDriverState *bs, uint64_t host_offset,
+                uint64_t guest_offset, void *buf, size_t len,
+                Qcow2EncDecFunc func)
 {
     BDRVQcow2State *s = bs->opaque;
+
     Qcow2EncDecData arg = {
         .block = s->crypto,
-        .offset = s->crypt_physical_offset ?
-                      file_cluster_offset + offset_into_cluster(s, offset) :
-                      offset,
+        .offset = s->crypt_physical_offset ? host_offset : guest_offset,
         .buf = buf,
         .len = len,
         .func = func,
@@ -251,18 +251,54 @@ qcow2_co_encdec(BlockDriverState *bs, uint64_t file_cluster_offset,
     return qcow2_co_process(bs, qcow2_encdec_pool_func, &arg);
 }
 
+
+/*
+ * qcow2_co_encrypt()
+ *
+ * Encrypts one or more contiguous aligned sectors
+ *
+ * @host_offset - underlying storage offset of the first sector of the
+ * data to be encrypted
+
+ * @guest_offset - guest (virtual) offset of the first sector of the
+ * data to be encrypted
+ *
+ * @buf - buffer with the data to encrypt, that after encryption
+ *        will be written to the underlying storage device at
+ *        @host_offset
+ *
+ * @len - length of the buffer (must be a BDRV_SECTOR_SIZE multiple)
+ *
+ * Depending on the encryption method, @host_cluster_offset and/or @guest_offset
+ * may be used for generating the initialization vector for
+ * encryption.
+ *
+ * Note that while the whole range must be aligned on sectors, it
+ * does not have to be aligned on clusters and can also cross cluster
+ * boundaries
+ *
+ */
 int coroutine_fn
-qcow2_co_encrypt(BlockDriverState *bs, uint64_t file_cluster_offset,
-                 uint64_t offset, void *buf, size_t len)
+qcow2_co_encrypt(BlockDriverState *bs, uint64_t host_offset,
+                 uint64_t guest_offset, void *buf, size_t len)
 {
-    return qcow2_co_encdec(bs, file_cluster_offset, offset, buf, len,
-                             qcrypto_block_encrypt);
+    return qcow2_co_encdec(bs, host_offset, guest_offset, buf, len,
+                           qcrypto_block_encrypt);
 }
 
+
+/*
+ * qcow2_co_decrypt()
+ *
+ * Decrypts one or more contiguous aligned sectors
+ * Similar to qcow2_co_encrypt
+ *
+ */
+
 int coroutine_fn
-qcow2_co_decrypt(BlockDriverState *bs, uint64_t file_cluster_offset,
-                 uint64_t offset, void *buf, size_t len)
+qcow2_co_decrypt(BlockDriverState *bs, uint64_t host_offset,
+                 uint64_t guest_offset, void *buf, size_t len)
 {
-    return qcow2_co_encdec(bs, file_cluster_offset, offset, buf, len,
-                             qcrypto_block_decrypt);
+    return qcow2_co_encdec(bs, host_offset, guest_offset, buf, len,
+                           qcrypto_block_decrypt);
 }
diff --git a/block/qcow2.c b/block/qcow2.c
index 0882ff6e92..7ec50157e0 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -2065,7 +2065,8 @@ static coroutine_fn int qcow2_co_preadv_part(BlockDriverState *bs,
 
                 assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
                 assert((cur_bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
-                if (qcow2_co_decrypt(bs, cluster_offset, offset,
+                if (qcow2_co_decrypt(bs, cluster_offset + offset_in_cluster,
+                                     offset,
                                      cluster_data, cur_bytes) < 0) {
                     ret = -EIO;
                     goto fail;
@@ -2284,7 +2285,7 @@ static coroutine_fn int qcow2_co_pwritev_part(
             qemu_iovec_to_buf(qiov, qiov_offset + bytes_done,
                               cluster_data, cur_bytes);
 
-            if (qcow2_co_encrypt(bs, cluster_offset, offset,
+            if (qcow2_co_encrypt(bs, cluster_offset + offset_in_cluster, offset,
                                  cluster_data, cur_bytes) < 0) {
                 ret = -EIO;
                 goto out_unlocked;
diff --git a/block/qcow2.h b/block/qcow2.h
index 998bcdaef1..a488d761ff 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -758,10 +758,10 @@ ssize_t coroutine_fn
 qcow2_co_decompress(BlockDriverState *bs, void *dest, size_t dest_size,
                     const void *src, size_t src_size);
 int coroutine_fn
-qcow2_co_encrypt(BlockDriverState *bs, uint64_t file_cluster_offset,
-                 uint64_t offset, void *buf, size_t len);
+qcow2_co_encrypt(BlockDriverState *bs, uint64_t host_offset,
+                 uint64_t guest_offset, void *buf, size_t len);
 int coroutine_fn
-qcow2_co_decrypt(BlockDriverState *bs, uint64_t file_cluster_offset,
-                 uint64_t offset, void *buf, size_t len);
+qcow2_co_decrypt(BlockDriverState *bs, uint64_t host_offset,
+                 uint64_t guest_offset, void *buf, size_t len);
 
 #endif
