* [PATCH v4 1/3] crypto: skcipher - add per-request data_unit_size with auto-splitting
2026-06-15 11:14 [PATCH v4 0/3] crypto: skcipher - per-request multi-data-unit batching Leonid Ravich
@ 2026-06-15 11:14 ` Leonid Ravich
2026-06-15 11:14 ` [PATCH v4 2/3] crypto: testmgr - test for multi-data-unit dispatch Leonid Ravich
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: Leonid Ravich @ 2026-06-15 11:14 UTC (permalink / raw)
To: Herbert Xu
Cc: Alasdair Kergon, Ard Biesheuvel, Eric Biggers, Jens Axboe,
Horia Geanta, Gilad Ben-Yossef, linux-crypto, dm-devel,
linux-block
Add a data_unit_size field to struct skcipher_request that lets a
caller submit several data units (typically 512..4096-byte sectors)
sharing one starting IV in a single request. Algorithms derive each
data unit's IV from the caller-supplied IV by treating it as a
128-bit little-endian counter and adding the data-unit index, which
matches the layout produced by dm-crypt's plain64 IV mode and by
typical inline-encryption hardware.
This mirrors the data_unit_size concept already exposed by
struct blk_crypto_config for inline encryption.
The crypto API auto-splits a multi-data-unit request into per-DU
sub-requests when the underlying algorithm does not advertise
CRYPTO_ALG_SKCIPHER_NATIVE_MULTI_DU (a type-specific cra_flags bit,
defined in crypto/internal/skcipher.h). A consumer sets
data_unit_size and submits: a native driver handles all units in one
pass, otherwise the core splits transparently. The split derives
per-DU IVs as a 128-bit LE counter, so this is correct only for
algorithms using that IV convention (e.g. XTS with plain64-style
IVs); callers are responsible for that match, as they already are for
the IV itself.
skcipher_request_set_tfm() resets the field to 0 so a request reused
from a pool or stack defaults to single-data-unit semantics; callers
that want batching set it explicitly via
skcipher_request_set_data_unit_size() after configuring the tfm.
crypto_skcipher_encrypt()/decrypt() call
crypto_skcipher_validate_multi_du() before any algorithm dispatch.
data_unit_size must be a power of two when non-zero (realistic sizes
are 512..4096, letting the per-DU loop and the cryptlen alignment
check use a mask instead of a divide) and cryptlen a positive
multiple of it; a malformed geometry is rejected with -EINVAL. A
target that cannot do multi-DU - ivsize != SKCIPHER_MDU_IVSIZE (16),
an lskcipher, or an async algorithm without the native flag - is
rejected with -EOPNOTSUPP so a caller can fall back. Async is
excluded because the splitter dispatches synchronously: an
-EINPROGRESS return would leave later units unsubmitted while the
driver still owned the request's scatterlists and IV. The check
gates the native path too, so algorithms never see a malformed
multi-DU request.
No in-tree algorithm sets CRYPTO_ALG_SKCIPHER_NATIVE_MULTI_DU yet;
subsequent patches add the testmgr coverage and the dm-crypt
consumer.
Signed-off-by: Leonid Ravich <lravich@amazon.com>
---
crypto/skcipher.c | 132 +++++++++++++++++++++++++++++
include/crypto/internal/skcipher.h | 10 +++
include/crypto/skcipher.h | 28 ++++++
3 files changed, 170 insertions(+)
diff --git a/crypto/skcipher.c b/crypto/skcipher.c
index 2b31d1d5d268..9262b47acfb9 100644
--- a/crypto/skcipher.c
+++ b/crypto/skcipher.c
@@ -17,6 +17,7 @@
#include <linux/cryptouser.h>
#include <linux/err.h>
#include <linux/kernel.h>
+#include <linux/log2.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/seq_file.h>
@@ -432,15 +433,139 @@ int crypto_skcipher_setkey(struct crypto_skcipher *tfm, const u8 *key,
}
EXPORT_SYMBOL_GPL(crypto_skcipher_setkey);
+/* IV size for the 128-bit LE-counter multi-data-unit convention. */
+#define SKCIPHER_MDU_IVSIZE 16
+
+static inline void skcipher_iv_inc_le128(u8 *iv)
+{
+ __le64 lo_le, hi_le;
+ u64 lo;
+
+ memcpy(&lo_le, iv, 8);
+ memcpy(&hi_le, iv + 8, 8);
+ lo = le64_to_cpu(lo_le) + 1;
+ lo_le = cpu_to_le64(lo);
+ memcpy(iv, &lo_le, 8);
+ if (unlikely(lo == 0)) {
+ hi_le = cpu_to_le64(le64_to_cpu(hi_le) + 1);
+ memcpy(iv + 8, &hi_le, 8);
+ }
+}
+
+/*
+ * Dispatch a multi-data-unit request as one single-DU sub-request per
+ * unit. Each unit's IV is the caller's IV plus the unit index, taken
+ * as a 128-bit little-endian counter. A pair of scatter_walks advances
+ * through src/dst in a single linear pass (O(entries + units)); building
+ * each sub-request's view with scatterwalk_ffwd() would instead rescan
+ * from the head every unit, i.e. O(units^2).
+ */
+static int skcipher_split_data_units(struct skcipher_request *req,
+ int (*body)(struct skcipher_request *))
+{
+ const unsigned int du = req->data_unit_size;
+ const unsigned int total = req->cryptlen;
+ struct scatterlist *orig_src = req->src;
+ struct scatterlist *orig_dst = req->dst;
+ bool inplace = orig_src == orig_dst;
+ struct scatter_walk src_walk, dst_walk;
+ struct scatterlist src_sg[2], dst_sg[2];
+ u8 iv_orig[SKCIPHER_MDU_IVSIZE];
+ u8 iv_work[SKCIPHER_MDU_IVSIZE];
+ unsigned int off;
+ int err = 0;
+
+ memcpy(iv_orig, req->iv, sizeof(iv_orig));
+ memcpy(iv_work, iv_orig, sizeof(iv_orig));
+
+ sg_init_table(src_sg, 2);
+ scatterwalk_start(&src_walk, orig_src);
+ if (!inplace) {
+ sg_init_table(dst_sg, 2);
+ scatterwalk_start(&dst_walk, orig_dst);
+ }
+
+ /* Stop the per-DU body from re-entering the splitter. */
+ req->data_unit_size = 0;
+ req->src = src_sg;
+ req->dst = inplace ? src_sg : dst_sg;
+
+ for (off = 0; off < total; off += du) {
+ req->cryptlen = du;
+ scatterwalk_get_sglist(&src_walk, src_sg);
+ scatterwalk_skip(&src_walk, du);
+ if (!inplace) {
+ scatterwalk_get_sglist(&dst_walk, dst_sg);
+ scatterwalk_skip(&dst_walk, du);
+ }
+
+ err = body(req);
+ if (err)
+ break;
+
+ skcipher_iv_inc_le128(iv_work);
+ memcpy(req->iv, iv_work, sizeof(iv_work));
+ }
+
+ /* Caller-visible IV is the starting IV regardless of outcome. */
+ memcpy(req->iv, iv_orig, sizeof(iv_orig));
+ req->src = orig_src;
+ req->dst = orig_dst;
+ req->cryptlen = total;
+ req->data_unit_size = du;
+ return err;
+}
+
+static int crypto_skcipher_validate_multi_du(struct skcipher_request *req)
+{
+ const unsigned int du = req->data_unit_size;
+ struct crypto_skcipher *tfm;
+ struct skcipher_alg *alg;
+ u32 cra_flags;
+
+ if (likely(!du))
+ return 0;
+ if (!is_power_of_2(du) || du < SKCIPHER_MDU_IVSIZE)
+ return -EINVAL;
+ if (!req->cryptlen || (req->cryptlen & (du - 1)))
+ return -EINVAL;
+
+ tfm = crypto_skcipher_reqtfm(req);
+ alg = crypto_skcipher_alg(tfm);
+
+ /* lskcipher's *_sg path doesn't honour data_unit_size. */
+ if (alg->co.base.cra_type != &crypto_skcipher_type)
+ return -EOPNOTSUPP;
+
+ /* Capability mismatch, not a malformed request: report -EOPNOTSUPP. */
+ if (crypto_skcipher_ivsize(tfm) != SKCIPHER_MDU_IVSIZE)
+ return -EOPNOTSUPP;
+
+ /* The auto-splitter is sync-only; native drivers own async dispatch. */
+ cra_flags = alg->co.base.cra_flags;
+ if ((cra_flags & CRYPTO_ALG_ASYNC) &&
+ !(cra_flags & CRYPTO_ALG_SKCIPHER_NATIVE_MULTI_DU))
+ return -EOPNOTSUPP;
+
+ return 0;
+}
+
int crypto_skcipher_encrypt(struct skcipher_request *req)
{
struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
struct skcipher_alg *alg = crypto_skcipher_alg(tfm);
+ int err;
if (crypto_skcipher_get_flags(tfm) & CRYPTO_TFM_NEED_KEY)
return -ENOKEY;
+ err = crypto_skcipher_validate_multi_du(req);
+ if (err)
+ return err;
if (alg->co.base.cra_type != &crypto_skcipher_type)
return crypto_lskcipher_encrypt_sg(req);
+ if (req->data_unit_size &&
+ !(alg->co.base.cra_flags & CRYPTO_ALG_SKCIPHER_NATIVE_MULTI_DU))
+ return skcipher_split_data_units(req, alg->encrypt);
return alg->encrypt(req);
}
EXPORT_SYMBOL_GPL(crypto_skcipher_encrypt);
@@ -449,11 +574,18 @@ int crypto_skcipher_decrypt(struct skcipher_request *req)
{
struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
struct skcipher_alg *alg = crypto_skcipher_alg(tfm);
+ int err;
if (crypto_skcipher_get_flags(tfm) & CRYPTO_TFM_NEED_KEY)
return -ENOKEY;
+ err = crypto_skcipher_validate_multi_du(req);
+ if (err)
+ return err;
if (alg->co.base.cra_type != &crypto_skcipher_type)
return crypto_lskcipher_decrypt_sg(req);
+ if (req->data_unit_size &&
+ !(alg->co.base.cra_flags & CRYPTO_ALG_SKCIPHER_NATIVE_MULTI_DU))
+ return skcipher_split_data_units(req, alg->decrypt);
return alg->decrypt(req);
}
EXPORT_SYMBOL_GPL(crypto_skcipher_decrypt);
diff --git a/include/crypto/internal/skcipher.h b/include/crypto/internal/skcipher.h
index a965b6aabf61..4c826f3bc715 100644
--- a/include/crypto/internal/skcipher.h
+++ b/include/crypto/internal/skcipher.h
@@ -21,6 +21,16 @@
*/
#define CRYPTO_ALG_SKCIPHER_REQSIZE_LARGE CRYPTO_ALG_OPTIONAL_KEY
+/*
+ * Set by an skcipher that handles skcipher_request::data_unit_size > 0
+ * natively in one pass; otherwise the API splits the request. Lives in
+ * the type-specific 0xff000000 cra_flags range. A native driver must
+ * derive per-DU IVs as a 128-bit LE counter and leave @iv at the
+ * caller-supplied starting value on return, success or error, matching
+ * the auto-splitter so the two paths are observably identical.
+ */
+#define CRYPTO_ALG_SKCIPHER_NATIVE_MULTI_DU 0x01000000
+
struct aead_request;
struct rtattr;
diff --git a/include/crypto/skcipher.h b/include/crypto/skcipher.h
index 4efe2ca8c4d1..ced1fae08147 100644
--- a/include/crypto/skcipher.h
+++ b/include/crypto/skcipher.h
@@ -31,6 +31,11 @@ struct scatterlist;
/**
* struct skcipher_request - Symmetric key cipher request
* @cryptlen: Number of bytes to encrypt or decrypt
+ * @data_unit_size: Size in bytes of each data unit, or 0 for a
+ * single-data-unit request (the default). When non-zero,
+ * must be a power of two, @cryptlen must be a positive
+ * multiple of it, and per-DU IVs are derived from @iv as a
+ * 128-bit little-endian counter.
* @iv: Initialisation Vector
* @src: Source SG list
* @dst: Destination SG list
@@ -39,6 +44,7 @@ struct scatterlist;
*/
struct skcipher_request {
unsigned int cryptlen;
+ unsigned int data_unit_size;
u8 *iv;
@@ -225,6 +231,7 @@ struct lskcipher_alg {
struct skcipher_request *name = \
(((struct skcipher_request *)__##name##_desc)->base.tfm = \
crypto_sync_skcipher_tfm((_tfm)), \
+ ((struct skcipher_request *)__##name##_desc)->data_unit_size = 0, \
(void *)__##name##_desc)
/**
@@ -819,6 +826,8 @@ static inline void skcipher_request_set_tfm(struct skcipher_request *req,
struct crypto_skcipher *tfm)
{
req->base.tfm = crypto_skcipher_tfm(tfm);
+ /* Reused requests default to single-data-unit. */
+ req->data_unit_size = 0;
}
static inline void skcipher_request_set_sync_tfm(struct skcipher_request *req,
@@ -937,5 +946,24 @@ static inline void skcipher_request_set_crypt(
req->iv = iv;
}
+/**
+ * skcipher_request_set_data_unit_size() - submit as multiple data units
+ * @req: request handle
+ * @data_unit_size: data-unit size in bytes (power of two), or 0 to disable
+ *
+ * Process @req as @cryptlen / @data_unit_size data units sharing one starting
+ * @iv, with per-DU IVs derived as a 128-bit little-endian counter. @cryptlen
+ * must be a positive multiple of @data_unit_size, else the encrypt/decrypt
+ * call returns -EINVAL; a target that cannot do multi-DU (ivsize != 16, an
+ * lskcipher, or async without native support) returns -EOPNOTSUPP. Unlike
+ * the single-DU path, @iv is preserved across the call regardless of outcome.
+ */
+static inline void
+skcipher_request_set_data_unit_size(struct skcipher_request *req,
+ unsigned int data_unit_size)
+{
+ req->data_unit_size = data_unit_size;
+}
+
#endif /* _CRYPTO_SKCIPHER_H */
base-commit: a8cafdf8c949f17c92eca0045532e88ac0dac30d
--
2.47.3
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH v4 2/3] crypto: testmgr - test for multi-data-unit dispatch
2026-06-15 11:14 [PATCH v4 0/3] crypto: skcipher - per-request multi-data-unit batching Leonid Ravich
2026-06-15 11:14 ` [PATCH v4 1/3] crypto: skcipher - add per-request data_unit_size with auto-splitting Leonid Ravich
@ 2026-06-15 11:14 ` Leonid Ravich
2026-06-15 11:14 ` [PATCH v4 3/3] dm crypt: batch all sectors of a bio per crypto request Leonid Ravich
2026-06-15 22:53 ` [PATCH v4 0/3] crypto: skcipher - per-request multi-data-unit batching Eric Biggers
3 siblings, 0 replies; 5+ messages in thread
From: Leonid Ravich @ 2026-06-15 11:14 UTC (permalink / raw)
To: Herbert Xu
Cc: Alasdair Kergon, Ard Biesheuvel, Eric Biggers, Jens Axboe,
Horia Geanta, Gilad Ben-Yossef, linux-crypto, dm-devel,
linux-block
Add a test that runs on every skcipher with ivsize == 16. It
encrypts random plaintext two ways and compares:
1. one batched request with skcipher_request_set_data_unit_size()
set, over a deliberately fragmented scatterlist whose entries do
not align to the data-unit size (so per-DU views cross SG entries
and exercise the scatter_walk cursor), and
2. an independent reference of N single-DU requests with IVs walked
as a 128-bit LE counter, matching the convention documented in
skcipher_request_set_data_unit_size().
The two must produce byte-identical ciphertext; this pins the IV
convention rather than only checking encrypt/decrypt symmetry. The
batched ciphertext is then round-tripped back to plaintext, and the
caller IV is checked unchanged. Iterates over typical data unit
sizes (512, 1024, 2048, 4096).
Algorithms the validator rejects for multi-DU return -EOPNOTSUPP on
the first call and skip cleanly; a genuine mismatch returns -EBADMSG
so it cannot be confused with a skip.
Signed-off-by: Leonid Ravich <lravich@amazon.com>
---
crypto/testmgr.c | 192 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 192 insertions(+)
diff --git a/crypto/testmgr.c b/crypto/testmgr.c
index 4d86efae65b2..5cbd0f4b070e 100644
--- a/crypto/testmgr.c
+++ b/crypto/testmgr.c
@@ -3211,6 +3211,194 @@ static int test_skcipher(int enc, const struct cipher_test_suite *suite,
return 0;
}
+/* Increment a 16-byte IV as a little-endian 128-bit counter. */
+static void test_mdu_iv_inc(u8 iv[16])
+{
+ int i;
+
+ for (i = 0; i < 16; i++)
+ if (++iv[i])
+ break;
+}
+
+/*
+ * Encrypt one du_size block with a plain single-DU request; used to
+ * build an independent reference for the batched dispatch.
+ */
+static int test_mdu_ref_encrypt(struct crypto_skcipher *tfm, const u8 *in,
+ u8 *out, unsigned int du_size, const u8 iv[16])
+{
+ struct skcipher_request *req;
+ struct scatterlist sg_in, sg_out;
+ DECLARE_CRYPTO_WAIT(wait);
+ u8 ivbuf[16];
+ int err;
+
+ req = skcipher_request_alloc(tfm, GFP_KERNEL);
+ if (!req)
+ return -ENOMEM;
+ memcpy(ivbuf, iv, 16);
+ memcpy(out, in, du_size);
+ sg_init_one(&sg_in, out, du_size);
+ skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
+ CRYPTO_TFM_REQ_MAY_SLEEP,
+ crypto_req_done, &wait);
+ skcipher_request_set_crypt(req, &sg_in, &sg_in, du_size, ivbuf);
+ err = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
+ skcipher_request_free(req);
+ return err;
+}
+
+/*
+ * Build a deliberately fragmented SG over @buf: entries that do not
+ * align to du_size, so the splitter's per-DU views cross SG entries
+ * and exercise the scatter_walk cursor.
+ */
+static void test_mdu_sg_fragment(struct scatterlist *sg, unsigned int nents,
+ u8 *buf, unsigned int total)
+{
+ unsigned int chunk = total / nents;
+ unsigned int off = 0, i;
+
+ sg_init_table(sg, nents);
+ for (i = 0; i < nents; i++) {
+ unsigned int len = (i == nents - 1) ? total - off : chunk;
+
+ sg_set_buf(&sg[i], buf + off, len);
+ off += len;
+ }
+}
+
+/*
+ * Multi-DU test: verify the batched dispatch produces byte-identical
+ * ciphertext to an independent N x single-DU reference with per-DU IVs
+ * walked as a 128-bit LE counter (pins the IV convention, not just
+ * enc/dec symmetry), over a fragmented SG, then round-trips. Real
+ * mismatches return -EBADMSG; ineligible algorithms skip via the
+ * validator's -EOPNOTSUPP.
+ */
+#define TEST_MDU_NR_UNITS 4
+#define TEST_MDU_NR_FRAGS 5
+static int test_skcipher_multi_du_one(struct crypto_skcipher *tfm,
+ unsigned int du_size)
+{
+ const char *driver = crypto_skcipher_driver_name(tfm);
+ const unsigned int total = du_size * TEST_MDU_NR_UNITS;
+ struct skcipher_request *req = NULL;
+ struct scatterlist sg[TEST_MDU_NR_FRAGS];
+ DECLARE_CRYPTO_WAIT(wait);
+ u8 iv_orig[16], iv_work[16], iv_ref[16];
+ u8 *plain = NULL, *buf = NULL, *ref = NULL;
+ unsigned int u;
+ int err;
+
+ plain = kmalloc(total, GFP_KERNEL);
+ buf = kmalloc(total, GFP_KERNEL);
+ ref = kmalloc(total, GFP_KERNEL);
+ req = skcipher_request_alloc(tfm, GFP_KERNEL);
+ if (!plain || !buf || !ref || !req) {
+ err = -ENOMEM;
+ goto out;
+ }
+
+ get_random_bytes(plain, total);
+ get_random_bytes(iv_orig, sizeof(iv_orig));
+
+ /* Reference: per-DU single requests with LE128-walked IVs. */
+ memcpy(iv_ref, iv_orig, sizeof(iv_orig));
+ for (u = 0; u < TEST_MDU_NR_UNITS; u++) {
+ err = test_mdu_ref_encrypt(tfm, plain + u * du_size,
+ ref + u * du_size, du_size, iv_ref);
+ /* First single-DU call reveals an ineligible algorithm. */
+ if (err == -EOPNOTSUPP && u == 0)
+ goto out;
+ if (err) {
+ pr_err("alg: skcipher: %s multi-DU ref encrypt failed (du=%u): %d\n",
+ driver, du_size, err);
+ goto out;
+ }
+ test_mdu_iv_inc(iv_ref);
+ }
+
+ /* Batched: one request over a fragmented SG. */
+ memcpy(buf, plain, total);
+ memcpy(iv_work, iv_orig, sizeof(iv_orig));
+ test_mdu_sg_fragment(sg, TEST_MDU_NR_FRAGS, buf, total);
+ skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
+ CRYPTO_TFM_REQ_MAY_SLEEP,
+ crypto_req_done, &wait);
+ skcipher_request_set_crypt(req, sg, sg, total, iv_work);
+ skcipher_request_set_data_unit_size(req, du_size);
+ err = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
+ if (err == -EOPNOTSUPP)
+ goto out;
+ if (err) {
+ pr_err("alg: skcipher: %s multi-DU encrypt failed (du=%u): %d\n",
+ driver, du_size, err);
+ goto out;
+ }
+ if (memcmp(buf, ref, total) != 0) {
+ pr_err("alg: skcipher: %s multi-DU ciphertext differs from single-DU reference (du=%u)\n",
+ driver, du_size);
+ err = -EBADMSG;
+ goto out;
+ }
+ /* req->iv must be unchanged after multi-DU dispatch. */
+ if (memcmp(iv_work, iv_orig, sizeof(iv_orig)) != 0) {
+ pr_err("alg: skcipher: %s multi-DU encrypt mutated caller IV (du=%u)\n",
+ driver, du_size);
+ err = -EBADMSG;
+ goto out;
+ }
+
+ /* Round-trip the batched ciphertext back to plaintext. */
+ test_mdu_sg_fragment(sg, TEST_MDU_NR_FRAGS, buf, total);
+ skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
+ CRYPTO_TFM_REQ_MAY_SLEEP,
+ crypto_req_done, &wait);
+ skcipher_request_set_crypt(req, sg, sg, total, iv_work);
+ skcipher_request_set_data_unit_size(req, du_size);
+ err = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
+ if (err) {
+ pr_err("alg: skcipher: %s multi-DU decrypt failed (du=%u): %d\n",
+ driver, du_size, err);
+ goto out;
+ }
+ if (memcmp(buf, plain, total) != 0) {
+ pr_err("alg: skcipher: %s multi-DU round-trip mismatch (du=%u)\n",
+ driver, du_size);
+ err = -EBADMSG;
+ }
+
+out:
+ skcipher_request_free(req);
+ kfree(ref);
+ kfree(buf);
+ kfree(plain);
+ return err;
+}
+
+static int test_skcipher_multi_du(struct crypto_skcipher *tfm)
+{
+ static const unsigned int du_sizes[] = { 512, 1024, 2048, 4096 };
+ unsigned int j;
+ int err;
+
+ if (crypto_skcipher_ivsize(tfm) != 16)
+ return 0;
+
+ for (j = 0; j < ARRAY_SIZE(du_sizes); j++) {
+ err = test_skcipher_multi_du_one(tfm, du_sizes[j]);
+ /* Ineligible algorithms skip; real failures propagate. */
+ if (err == -EOPNOTSUPP)
+ return 0;
+ if (err)
+ return err;
+ cond_resched();
+ }
+ return 0;
+}
+
static int alg_test_skcipher(const struct alg_test_desc *desc,
const char *driver, u32 type, u32 mask)
{
@@ -3259,6 +3447,10 @@ static int alg_test_skcipher(const struct alg_test_desc *desc,
if (err)
goto out;
+ err = test_skcipher_multi_du(tfm);
+ if (err)
+ goto out;
+
err = test_skcipher_vs_generic_impl(desc->generic_driver, req, tsgls);
out:
free_cipher_test_sglists(tsgls);
--
2.47.3
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH v4 3/3] dm crypt: batch all sectors of a bio per crypto request
2026-06-15 11:14 [PATCH v4 0/3] crypto: skcipher - per-request multi-data-unit batching Leonid Ravich
2026-06-15 11:14 ` [PATCH v4 1/3] crypto: skcipher - add per-request data_unit_size with auto-splitting Leonid Ravich
2026-06-15 11:14 ` [PATCH v4 2/3] crypto: testmgr - test for multi-data-unit dispatch Leonid Ravich
@ 2026-06-15 11:14 ` Leonid Ravich
2026-06-15 22:53 ` [PATCH v4 0/3] crypto: skcipher - per-request multi-data-unit batching Eric Biggers
3 siblings, 0 replies; 5+ messages in thread
From: Leonid Ravich @ 2026-06-15 11:14 UTC (permalink / raw)
To: Herbert Xu
Cc: Alasdair Kergon, Ard Biesheuvel, Eric Biggers, Jens Axboe,
Horia Geanta, Gilad Ben-Yossef, linux-crypto, dm-devel,
linux-block
Submit one skcipher request per bio with
skcipher_request_set_data_unit_size(req, cc->sector_size) instead of
issuing one request per sector. This removes per-sector overhead in
the crypto API hot path: request allocation, callback dispatch,
completion handling, and SG setup.
The optimisation is enabled automatically at table load when all
of the following hold:
- the cipher is non-aead (i.e. skcipher), sync, tfms_count 1;
- the IV mode advertises sector_iv_le128, i.e. its per-sector IV
advances as a 128-bit LE counter, matching the convention
documented in skcipher_request_set_data_unit_size(). Only plain64
sets it today (its 64-bit LE counter extends correctly); plain is
excluded as its 32-bit counter wraps differently across a
2^32-sector boundary;
- ivsize is 16 (the core rejects other sizes with -EOPNOTSUPP);
- the iv_gen_ops->post() hook is unset;
- dm-integrity is not stacked (no integrity tag or integrity IV).
The cipher driver does not need to advertise anything: the crypto
API auto-splits multi-data-unit requests for drivers that cannot
handle them natively, so dm-crypt sees the same fast batched
submission contract regardless of the underlying driver.
A new CRYPT_MULTI_DATA_UNIT cipher_flag, set once at construction
time, gates the multi-data-unit dispatch. The existing per-sector
path in crypt_convert_block_skcipher() is unchanged; the new
crypt_convert_block_skcipher_multi() is reached from a small
dispatch in crypt_convert() and shares the same backlog/-EBUSY/
-EINPROGRESS flow control with the per-sector path.
Heap-allocated scatterlists are stashed in dm_crypt_request and
freed in crypt_free_req_skcipher() to avoid races between the
synchronous-success free path and async-completion reuse from the
request pool. On scatterlist allocation failure the helper returns
-EAGAIN, and the core returns -EOPNOTSUPP if a driver turns out
unable to do multi-DU; crypt_convert() handles both by clearing its
local multi_du flag and falling back to the per-sector path for the
rest of the current crypt_convert() invocation, ensuring forward progress
on the swap-out-to-dm-crypt path even under total memory exhaustion
(the per-sector path uses only cc->req_pool, a mempool with
reservoir set up at table-load time, and the inline
dmreq->sg_in[]/sg_out[] arrays — no allocation that could fail).
Verified end-to-end with a byte-equivalence test: encrypted output
of plain64 dm-crypt with the multi-data-unit path matches output of
the single-data-unit path bit-for-bit over a 256 MB device, with
xts-aes-aesni driving the auto-split path.
Signed-off-by: Leonid Ravich <lravich@amazon.com>
---
drivers/md/dm-crypt.c | 215 ++++++++++++++++++++++++++++++++++++++++--
1 file changed, 207 insertions(+), 8 deletions(-)
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 608b617fb817..bfb98dd876d7 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -101,6 +101,9 @@ struct dm_crypt_request {
struct scatterlist sg_in[4];
struct scatterlist sg_out[4];
u64 iv_sector;
+ /* Multi-data-unit SG arrays, NULL when sg_in[]/sg_out[] suffice. */
+ struct scatterlist *sg_in_ext;
+ struct scatterlist *sg_out_ext;
};
struct crypt_config;
@@ -115,6 +118,12 @@ struct crypt_iv_operations {
struct dm_crypt_request *dmreq);
void (*post)(struct crypt_config *cc, u8 *iv,
struct dm_crypt_request *dmreq);
+ /*
+ * The per-sector IV advances as a 128-bit LE counter, so a bio's
+ * consecutive sectors share one starting IV and can be batched into
+ * a single skcipher request via data_unit_size.
+ */
+ bool sector_iv_le128;
};
struct iv_benbi_private {
@@ -151,6 +160,7 @@ enum cipher_flags {
CRYPT_IV_LARGE_SECTORS, /* Calculate IV from sector_size, not 512B sectors */
CRYPT_ENCRYPT_PREPROCESS, /* Must preprocess data for encryption (elephant) */
CRYPT_KEY_MAC_SIZE_SET, /* The integrity_key_size option was used */
+ CRYPT_MULTI_DATA_UNIT, /* Batch all sectors of a bio per crypto request */
};
/*
@@ -1018,7 +1028,8 @@ static const struct crypt_iv_operations crypt_iv_plain_ops = {
};
static const struct crypt_iv_operations crypt_iv_plain64_ops = {
- .generator = crypt_iv_plain64_gen
+ .generator = crypt_iv_plain64_gen,
+ .sector_iv_le128 = true,
};
static const struct crypt_iv_operations crypt_iv_plain64be_ops = {
@@ -1426,12 +1437,126 @@ static int crypt_convert_block_skcipher(struct crypt_config *cc,
return r;
}
+/*
+ * Submit all remaining sectors of the current bio in one skcipher request.
+ * Same return convention as crypt_convert_block_skcipher() except for
+ * -EAGAIN, which the caller must treat as "disable multi-DU and re-enter
+ * the per-sector path" so swap-out-to-dm-crypt always makes forward
+ * progress on the mempool reserve.
+ */
+static int crypt_convert_block_skcipher_multi(struct crypt_config *cc,
+ struct convert_context *ctx,
+ struct skcipher_request *req,
+ unsigned int *out_processed)
+{
+ const unsigned int sector_size = cc->sector_size;
+ const gfp_t gfp = GFP_NOIO | __GFP_NORETRY | __GFP_NOWARN;
+ unsigned int total = ctx->iter_in.bi_size;
+ unsigned int n_sg_in = 0, n_sg_out = 0;
+ struct dm_crypt_request *dmreq = dmreq_of_req(cc, req);
+ struct scatterlist *sg_in = NULL, *sg_out = NULL;
+ struct bvec_iter iter_in, iter_out;
+ struct bio_vec bv;
+ u8 *iv, *org_iv;
+ int r;
+
+ if (WARN_ON_ONCE(ctx->iter_in.bi_size != ctx->iter_out.bi_size))
+ return -EIO;
+ if (unlikely(total & (sector_size - 1)))
+ return -EIO;
+
+ iter_in = ctx->iter_in;
+ iter_in.bi_size = total;
+ __bio_for_each_bvec(bv, ctx->bio_in, iter_in, iter_in)
+ n_sg_in++;
+
+ iter_out = ctx->iter_out;
+ iter_out.bi_size = total;
+ __bio_for_each_bvec(bv, ctx->bio_out, iter_out, iter_out)
+ n_sg_out++;
+
+ sg_in = kmalloc_array(n_sg_in, sizeof(*sg_in), gfp);
+ sg_out = (ctx->bio_in == ctx->bio_out) ? sg_in :
+ kmalloc_array(n_sg_out, sizeof(*sg_out), gfp);
+ if (!sg_in || !sg_out) {
+ kfree(sg_in);
+ if (sg_out != sg_in)
+ kfree(sg_out);
+ return -EAGAIN;
+ }
+
+ sg_init_table(sg_in, n_sg_in);
+ {
+ unsigned int i = 0;
+
+ iter_in = ctx->iter_in;
+ iter_in.bi_size = total;
+ __bio_for_each_bvec(bv, ctx->bio_in, iter_in, iter_in)
+ sg_set_page(&sg_in[i++], bv.bv_page, bv.bv_len,
+ bv.bv_offset);
+ }
+
+ if (sg_out != sg_in) {
+ unsigned int i = 0;
+
+ sg_init_table(sg_out, n_sg_out);
+ iter_out = ctx->iter_out;
+ iter_out.bi_size = total;
+ __bio_for_each_bvec(bv, ctx->bio_out, iter_out, iter_out)
+ sg_set_page(&sg_out[i++], bv.bv_page, bv.bv_len,
+ bv.bv_offset);
+ }
+
+ dmreq->iv_sector = ctx->cc_sector;
+ if (test_bit(CRYPT_IV_LARGE_SECTORS, &cc->cipher_flags))
+ dmreq->iv_sector >>= cc->sector_shift;
+ dmreq->ctx = ctx;
+
+ iv = iv_of_dmreq(cc, dmreq);
+ org_iv = org_iv_of_dmreq(cc, dmreq);
+ r = cc->iv_gen_ops->generator(cc, org_iv, dmreq);
+ if (r < 0)
+ goto out_free_sg;
+ memcpy(iv, org_iv, cc->iv_size);
+
+ dmreq->sg_in_ext = sg_in;
+ dmreq->sg_out_ext = (sg_out == sg_in) ? NULL : sg_out;
+
+ skcipher_request_set_crypt(req, sg_in, sg_out, total, iv);
+ skcipher_request_set_data_unit_size(req, sector_size);
+
+ if (bio_data_dir(ctx->bio_in) == WRITE)
+ r = crypto_skcipher_encrypt(req);
+ else
+ r = crypto_skcipher_decrypt(req);
+
+ /*
+ * Sync error: kcryptd_async_done won't run, so free the SG
+ * arrays here. Async returns (-EINPROGRESS, -EBUSY) hand
+ * ownership to the completion callback.
+ */
+ if (r && r != -EINPROGRESS && r != -EBUSY)
+ goto out_free_sg;
+
+ *out_processed = total;
+ return r;
+
+out_free_sg:
+ kfree(sg_in);
+ if (sg_out != sg_in)
+ kfree(sg_out);
+ dmreq->sg_in_ext = NULL;
+ dmreq->sg_out_ext = NULL;
+ return r;
+}
+
static void kcryptd_async_done(void *async_req, int error);
static int crypt_alloc_req_skcipher(struct crypt_config *cc,
struct convert_context *ctx)
{
unsigned int key_index = ctx->cc_sector & (cc->tfms_count - 1);
+ struct dm_crypt_request *dmreq;
if (!ctx->r.req) {
ctx->r.req = mempool_alloc(&cc->req_pool, in_interrupt() ? GFP_ATOMIC : GFP_NOIO);
@@ -1441,6 +1566,11 @@ static int crypt_alloc_req_skcipher(struct crypt_config *cc,
skcipher_request_set_tfm(ctx->r.req, cc->cipher_tfm.tfms[key_index]);
+ /* Multi-DU SG arrays are owned by the helper that allocates them. */
+ dmreq = dmreq_of_req(cc, ctx->r.req);
+ dmreq->sg_in_ext = NULL;
+ dmreq->sg_out_ext = NULL;
+
/*
* Use REQ_MAY_BACKLOG so a cipher driver internally backlogs
* requests if driver request queue is full.
@@ -1487,6 +1617,12 @@ static void crypt_free_req_skcipher(struct crypt_config *cc,
struct skcipher_request *req, struct bio *base_bio)
{
struct dm_crypt_io *io = dm_per_bio_data(base_bio, cc->per_bio_data_size);
+ struct dm_crypt_request *dmreq = dmreq_of_req(cc, req);
+
+ kfree(dmreq->sg_in_ext);
+ dmreq->sg_in_ext = NULL;
+ kfree(dmreq->sg_out_ext);
+ dmreq->sg_out_ext = NULL;
if ((struct skcipher_request *)(io + 1) != req)
mempool_free(req, &cc->req_pool);
@@ -1515,7 +1651,9 @@ static void crypt_free_req(struct crypt_config *cc, void *req, struct bio *base_
static blk_status_t crypt_convert(struct crypt_config *cc,
struct convert_context *ctx, bool atomic, bool reset_pending)
{
- unsigned int sector_step = cc->sector_size >> SECTOR_SHIFT;
+ const unsigned int sector_step = cc->sector_size >> SECTOR_SHIFT;
+ bool multi_du = test_bit(CRYPT_MULTI_DATA_UNIT, &cc->cipher_flags);
+ unsigned int processed;
int r;
/*
@@ -1536,8 +1674,13 @@ static blk_status_t crypt_convert(struct crypt_config *cc,
atomic_inc(&ctx->cc_pending);
+ processed = cc->sector_size;
if (crypt_integrity_aead(cc))
r = crypt_convert_block_aead(cc, ctx, ctx->r.req_aead, ctx->tag_offset);
+ else if (multi_du)
+ r = crypt_convert_block_skcipher_multi(cc, ctx,
+ ctx->r.req,
+ &processed);
else
r = crypt_convert_block_skcipher(cc, ctx, ctx->r.req, ctx->tag_offset);
@@ -1559,8 +1702,19 @@ static blk_status_t crypt_convert(struct crypt_config *cc,
* exit and continue processing in a workqueue
*/
ctx->r.req = NULL;
- ctx->tag_offset++;
- ctx->cc_sector += sector_step;
+ if (!multi_du) {
+ ctx->tag_offset++;
+ ctx->cc_sector += sector_step;
+ } else {
+ bio_advance_iter(ctx->bio_in,
+ &ctx->iter_in,
+ processed);
+ bio_advance_iter(ctx->bio_out,
+ &ctx->iter_out,
+ processed);
+ ctx->cc_sector +=
+ processed >> SECTOR_SHIFT;
+ }
return BLK_STS_DEV_RESOURCE;
}
} else {
@@ -1574,19 +1728,41 @@ static blk_status_t crypt_convert(struct crypt_config *cc,
*/
case -EINPROGRESS:
ctx->r.req = NULL;
- ctx->tag_offset++;
- ctx->cc_sector += sector_step;
+ if (!multi_du) {
+ ctx->tag_offset++;
+ ctx->cc_sector += sector_step;
+ } else {
+ bio_advance_iter(ctx->bio_in, &ctx->iter_in,
+ processed);
+ bio_advance_iter(ctx->bio_out, &ctx->iter_out,
+ processed);
+ ctx->cc_sector += processed >> SECTOR_SHIFT;
+ }
continue;
/*
* The request was already processed (synchronously).
*/
case 0:
atomic_dec(&ctx->cc_pending);
- ctx->cc_sector += sector_step;
- ctx->tag_offset++;
+ if (!multi_du) {
+ ctx->cc_sector += sector_step;
+ ctx->tag_offset++;
+ } else {
+ bio_advance_iter(ctx->bio_in, &ctx->iter_in,
+ processed);
+ bio_advance_iter(ctx->bio_out, &ctx->iter_out,
+ processed);
+ ctx->cc_sector += processed >> SECTOR_SHIFT;
+ }
if (!atomic)
cond_resched();
continue;
+ /* Multi-DU rejected (no memory or sync-only mismatch): fall back. */
+ case -EAGAIN:
+ case -EOPNOTSUPP:
+ atomic_dec(&ctx->cc_pending);
+ multi_du = false;
+ continue;
/*
* There was a data integrity error.
*/
@@ -3063,6 +3239,29 @@ static int crypt_ctr_cipher(struct dm_target *ti, char *cipher_in, char *key)
}
}
+ /*
+ * Enable multi-data-unit batching only when per-DU IVs can be
+ * derived from one starting IV as a 128-bit LE counter, matching
+ * skcipher_request_set_data_unit_size(). Only IV modes flagged
+ * sector_iv_le128 qualify (plain64; not plain, whose 32-bit counter
+ * wraps differently across a 2^32-sector boundary). ivsize must be
+ * 16 (the core rejects otherwise) and the cipher must be sync,
+ * single-tfm, no integrity, no per-sector post() hook. The driver
+ * advertises nothing: the core auto-splits for drivers that lack
+ * native support.
+ */
+ if (!crypt_integrity_aead(cc) && cc->tfms_count == 1 &&
+ cc->iv_gen_ops && cc->iv_gen_ops->sector_iv_le128 &&
+ !cc->iv_gen_ops->post &&
+ !cc->integrity_tag_size && !cc->integrity_iv_size &&
+ crypto_skcipher_ivsize(any_tfm(cc)) == 16 &&
+ !(crypto_skcipher_alg(any_tfm(cc))->base.cra_flags &
+ CRYPTO_ALG_ASYNC)) {
+ set_bit(CRYPT_MULTI_DATA_UNIT, &cc->cipher_flags);
+ DMINFO("Using multi-data-unit crypto offload (du=%u)",
+ cc->sector_size);
+ }
+
/* wipe the kernel key payload copy */
if (cc->key_string)
memset(cc->key, 0, cc->key_size * sizeof(u8));
--
2.47.3
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH v4 0/3] crypto: skcipher - per-request multi-data-unit batching
2026-06-15 11:14 [PATCH v4 0/3] crypto: skcipher - per-request multi-data-unit batching Leonid Ravich
` (2 preceding siblings ...)
2026-06-15 11:14 ` [PATCH v4 3/3] dm crypt: batch all sectors of a bio per crypto request Leonid Ravich
@ 2026-06-15 22:53 ` Eric Biggers
3 siblings, 0 replies; 5+ messages in thread
From: Eric Biggers @ 2026-06-15 22:53 UTC (permalink / raw)
To: Leonid Ravich
Cc: Herbert Xu, Alasdair Kergon, Ard Biesheuvel, Jens Axboe,
Horia Geanta, Gilad Ben-Yossef, linux-crypto, dm-devel,
linux-block
On Mon, Jun 15, 2026 at 11:14:56AM +0000, Leonid Ravich wrote:
> The series adds a per-request "data unit size" to the skcipher API
> so a caller can submit several data units (typically 512..4096-byte
> sectors) sharing one starting IV in a single request. Algorithms
> derive each data unit's IV from the caller-supplied IV by treating
> it as a 128-bit little-endian counter and adding the data-unit
> index, matching the layout produced by dm-crypt's plain64 IV mode
> and by typical inline-encryption hardware.
>
> This mirrors the data_unit_size concept already exposed by
> struct blk_crypto_config for inline encryption.
>
> The first user is dm-crypt, which today issues one skcipher request
> per sector and so pays a per-sector cost in request allocation,
> callback dispatch, completion handling, and scatterlist setup.
>
> Proof-of-concept performance numbers from the RFC reply [1]: +19%
> throughput / -40% CPU on a single-core arm64 system with a hardware
> XTS-AES-256 accelerator running fio 4 KiB sequential writes through
> dm-crypt, when an out-of-tree arm64 xts driver advertises
> CRYPTO_ALG_SKCIPHER_NATIVE_MULTI_DU. This series itself does not
> include arch enablement; the fast path is opt-in per driver, the
> slow path is universal via the auto-splitter.
>
> The native fast path amortises both per-sector dispatch and per-sector
> crypto setup across a bio - the measured win above, on an engine that
> offloads the AES compute. The auto-splitter is for correctness and
> reach: any consumer can set data_unit_size and get correct output with
> the per-request allocation/callback/completion cost removed, but it
> still issues one alg->encrypt per data unit, so on a software cipher it
> saves only dispatch overhead (no throughput figure claimed - that is
> hardware- and workload-dependent). What it guarantees unconditionally
> is byte-identical output (Verification below) at O(entries + units),
> walking the scatterlists with a pair of struct scatter_walk cursors
> rather than rescanning from the head per unit.
So in other words, this series slows down dm-crypt and crypto_skcipher
for everyone to optimize for an out-of-tree driver. And there's also no
benchmark showing that your driver is even worth it over just using the
CPU.
- Eric
^ permalink raw reply [flat|nested] 5+ messages in thread