[RFC,-next] crypto: add debug knob to force async crypto

diff --git a/crypto/Makefile b/crypto/Makefile
index 953a7e105e58..ce4f921b2bfe 100644
--- a/crypto/Makefile
+++ b/crypto/Makefile
@@ -11,6 +11,7 @@  obj-$(CONFIG_CRYPTO_FIPS) += fips.o
 
 crypto_algapi-$(CONFIG_PROC_FS) += proc.o
 crypto_algapi-y := algapi.o scatterwalk.o $(crypto_algapi-y)
+crypto_algapi-$(CONFIG_DEBUG_CRYPTO) += debugfs.o
 obj-$(CONFIG_CRYPTO_ALGAPI2) += crypto_algapi.o
 
 obj-$(CONFIG_CRYPTO_AEAD2) += aead.o
diff --git a/crypto/algapi.c b/crypto/algapi.c
index 4fe95c448047..b3b218e133e0 100644
--- a/crypto/algapi.c
+++ b/crypto/algapi.c
@@ -1098,11 +1098,13 @@  static int __init crypto_algapi_init(void)
 {
 	crypto_init_proc();
 	crypto_start_tests();
+	crypto_init_debugfs();
 	return 0;
 }
 
 static void __exit crypto_algapi_exit(void)
 {
+	crypto_exit_debugfs();
 	crypto_exit_proc();
 }
 
diff --git a/crypto/cryptd.c b/crypto/cryptd.c
index bbcc368b6a55..571b69441ca9 100644
--- a/crypto/cryptd.c
+++ b/crypto/cryptd.c
@@ -26,6 +26,7 @@ 
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/workqueue.h>
+#include "internal.h"
 
 static unsigned int cryptd_max_cpu_qlen = 1000;
 module_param(cryptd_max_cpu_qlen, uint, 0);
@@ -176,6 +177,8 @@  static void cryptd_queue_worker(struct work_struct *work)
 	if (!req)
 		return;
 
+	crypto_cryptd_delay();
+
 	if (backlog)
 		crypto_request_complete(backlog, -EINPROGRESS);
 	crypto_request_complete(req, 0);
diff --git a/crypto/debugfs.c b/crypto/debugfs.c
new file mode 100644
index 000000000000..f34a95f6bbfb
--- /dev/null
+++ b/crypto/debugfs.c
@@ -0,0 +1,38 @@ 
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/debugfs.h>
+#include <linux/delay.h>
+
+static struct dentry *crypto_debugfs_dir;
+static bool simd_force_async;
+static u32 cryptd_delay;
+
+bool crypto_simd_force_async(void)
+{
+	return simd_force_async;
+}
+
+void crypto_cryptd_delay(void)
+{
+	unsigned int d = READ_ONCE(cryptd_delay);
+
+	if (d)
+		msleep(d);
+}
+
+void __init crypto_init_debugfs(void)
+{
+	crypto_debugfs_dir = debugfs_create_dir("crypto", NULL);
+
+#if IS_ENABLED(CONFIG_CRYPTO_SIMD)
+	debugfs_create_bool("simd_force_async", 0644, crypto_debugfs_dir, &simd_force_async);
+#endif
+
+#if IS_ENABLED(CONFIG_CRYPTO_CRYPTD)
+	debugfs_create_u32("cryptd_delay_ms", 0644, crypto_debugfs_dir, &cryptd_delay);
+#endif
+}
+
+void __exit crypto_exit_debugfs(void)
+{
+	debugfs_remove_recursive(crypto_debugfs_dir);
+}
diff --git a/crypto/internal.h b/crypto/internal.h
index 63e59240d5fb..dfe0d859e51c 100644
--- a/crypto/internal.h
+++ b/crypto/internal.h
@@ -96,6 +96,25 @@  static inline void crypto_exit_proc(void)
 { }
 #endif
 
+#if IS_ENABLED(CONFIG_DEBUG_CRYPTO)
+void __init crypto_init_debugfs(void);
+void __exit crypto_exit_debugfs(void);
+
+bool crypto_simd_force_async(void);
+void crypto_cryptd_delay(void);
+#else
+static inline void crypto_init_debugfs(void)
+{ }
+static inline void crypto_exit_debugfs(void)
+{ }
+static inline bool crypto_simd_force_async(void)
+{
+	return false;
+}
+static inline void crypto_cryptd_delay(void)
+{ }
+#endif
+
 static inline unsigned int crypto_cipher_ctxsize(struct crypto_alg *alg)
 {
 	return alg->cra_ctxsize;
diff --git a/crypto/simd.c b/crypto/simd.c
index edaa479a1ec5..1833e9b7a061 100644
--- a/crypto/simd.c
+++ b/crypto/simd.c
@@ -35,6 +35,7 @@ 
 #include <linux/module.h>
 #include <linux/preempt.h>
 #include <asm/simd.h>
+#include "internal.h"
 
 /* skcipher support */
 
@@ -69,7 +70,7 @@  static int simd_skcipher_encrypt(struct skcipher_request *req)
 	subreq = skcipher_request_ctx(req);
 	*subreq = *req;
 
-	if (!crypto_simd_usable() ||
+	if (crypto_simd_force_async() || !crypto_simd_usable() ||
 	    (in_atomic() && cryptd_skcipher_queued(ctx->cryptd_tfm)))
 		child = &ctx->cryptd_tfm->base;
 	else
@@ -90,7 +91,7 @@  static int simd_skcipher_decrypt(struct skcipher_request *req)
 	subreq = skcipher_request_ctx(req);
 	*subreq = *req;
 
-	if (!crypto_simd_usable() ||
+	if (crypto_simd_force_async() || !crypto_simd_usable() ||
 	    (in_atomic() && cryptd_skcipher_queued(ctx->cryptd_tfm)))
 		child = &ctx->cryptd_tfm->base;
 	else
@@ -317,7 +318,7 @@  static int simd_aead_encrypt(struct aead_request *req)
 	subreq = aead_request_ctx(req);
 	*subreq = *req;
 
-	if (!crypto_simd_usable() ||
+	if (crypto_simd_force_async() || !crypto_simd_usable() ||
 	    (in_atomic() && cryptd_aead_queued(ctx->cryptd_tfm)))
 		child = &ctx->cryptd_tfm->base;
 	else
@@ -338,7 +339,7 @@  static int simd_aead_decrypt(struct aead_request *req)
 	subreq = aead_request_ctx(req);
 	*subreq = *req;
 
-	if (!crypto_simd_usable() ||
+	if (crypto_simd_force_async() || !crypto_simd_usable() ||
 	    (in_atomic() && cryptd_aead_queued(ctx->cryptd_tfm)))
 		child = &ctx->cryptd_tfm->base;
 	else
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index fbc89baf7de6..54de2223cbd4 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -679,6 +679,12 @@  source "net/Kconfig.debug"
 
 endmenu # "Networking Debugging"
 
+config DEBUG_CRYPTO
+	bool "Cryptographic API Debugging"
+	depends on DEBUG_KERNEL && CRYPTO && DEBUG_FS
+	help
+	  Enable debugging options in the core Cryptographic API.
+
 menu "Memory Debugging"
 
 source "mm/Kconfig.debug"