Re: [PATCH v3 1/4] s390/crypto: Replace cond_resched() with msleep(1)

[Peter Zijlstra <peterz@infradead.org>]

On Fri, Jul 31, 2026 at 09:44:57AM +0200, Holger Dengler wrote:

> > Yes, guest migration is very likely far more disruptive than most
> > anything else. Perhaps clarify the code comment to include some of this
> > explanation?
> 
> I agree, the comment is not telling all main key points. What about the
> following?
> 
> /*
>  * Protected key expired due to relocation to another
>  * host. The long runnning re-wrap has no asynchronous
>  * completion notification, so polling is required.
>  * Trigger a re-schedule of this request by returning
>  * -ENOSPC ("hardware queue full") to the crypto engine.
>  * To avoid immediately re-invocation of this callback,
>  * tell scheduler to voluntarily give up the CPU here.
>  */
> 
> (I would leave it up to Heiko to merge the comment in his series, or let
> Harald/me do it in a separate patch)

Right, perhaps something like so, avoiding the endless copy/paste ?

---
diff --git a/arch/s390/crypto/paes_s390.c b/arch/s390/crypto/paes_s390.c
index 8cfe6166c193..973436592318 100644
--- a/arch/s390/crypto/paes_s390.c
+++ b/arch/s390/crypto/paes_s390.c
@@ -548,16 +548,7 @@ static int ecb_paes_do_one_request(struct crypto_engine *engine, void *areq)
 
 	rc = ecb_paes_do_crypt(ctx, req_ctx, tested, true);
 	if (rc == -EKEYEXPIRED) {
-		/*
-		 * Protected key expired, conversion is in process.
-		 * Trigger a re-schedule of this request by returning
-		 * -ENOSPC ("hardware queue is full") to the crypto engine.
-		 * To avoid immediately re-invocation of this callback,
-		 * tell the scheduler to voluntarily give up the CPU here.
-		 */
-		cond_resched();
-		pr_debug("rescheduling request\n");
-		return -ENOSPC;
+		return pkey_handle_expired();
 	} else if (rc) {
 		skcipher_walk_done(walk, rc);
 	}
@@ -814,16 +805,7 @@ static int cbc_paes_do_one_request(struct crypto_engine *engine, void *areq)
 
 	rc = cbc_paes_do_crypt(ctx, req_ctx, tested, true);
 	if (rc == -EKEYEXPIRED) {
-		/*
-		 * Protected key expired, conversion is in process.
-		 * Trigger a re-schedule of this request by returning
-		 * -ENOSPC ("hardware queue is full") to the crypto engine.
-		 * To avoid immediately re-invocation of this callback,
-		 * tell the scheduler to voluntarily give up the CPU here.
-		 */
-		cond_resched();
-		pr_debug("rescheduling request\n");
-		return -ENOSPC;
+		return pkey_handle_expired();
 	} else if (rc) {
 		skcipher_walk_done(walk, rc);
 	}
@@ -1122,16 +1104,7 @@ static int ctr_paes_do_one_request(struct crypto_engine *engine, void *areq)
 
 	rc = ctr_paes_do_crypt(ctx, req_ctx, tested, true);
 	if (rc == -EKEYEXPIRED) {
-		/*
-		 * Protected key expired, conversion is in process.
-		 * Trigger a re-schedule of this request by returning
-		 * -ENOSPC ("hardware queue is full") to the crypto engine.
-		 * To avoid immediately re-invocation of this callback,
-		 * tell the scheduler to voluntarily give up the CPU here.
-		 */
-		cond_resched();
-		pr_debug("rescheduling request\n");
-		return -ENOSPC;
+		return pkey_handle_expired();
 	} else if (rc) {
 		skcipher_walk_done(walk, rc);
 	}
@@ -1565,16 +1538,7 @@ static int xts_paes_do_one_request(struct crypto_engine *engine, void *areq)
 
 	rc = xts_paes_do_crypt(ctx, req_ctx, tested, true);
 	if (rc == -EKEYEXPIRED) {
-		/*
-		 * Protected key expired, conversion is in process.
-		 * Trigger a re-schedule of this request by returning
-		 * -ENOSPC ("hardware queue is full") to the crypto engine.
-		 * To avoid immediately re-invocation of this callback,
-		 * tell the scheduler to voluntarily give up the CPU here.
-		 */
-		cond_resched();
-		pr_debug("rescheduling request\n");
-		return -ENOSPC;
+		return pkey_handle_expired();
 	} else if (rc) {
 		skcipher_walk_done(walk, rc);
 	}
diff --git a/arch/s390/crypto/phmac_s390.c b/arch/s390/crypto/phmac_s390.c
index 03ca33ffe6cc..020a1beb2e22 100644
--- a/arch/s390/crypto/phmac_s390.c
+++ b/arch/s390/crypto/phmac_s390.c
@@ -887,16 +887,7 @@ static int phmac_do_one_request(struct crypto_engine *engine, void *areq)
 	case OP_FINUP:
 		rc = phmac_kmac_update(req, true);
 		if (rc == -EKEYEXPIRED) {
-			/*
-			 * Protected key expired, conversion is in process.
-			 * Trigger a re-schedule of this request by returning
-			 * -ENOSPC ("hardware queue full") to the crypto engine.
-			 * To avoid immediately re-invocation of this callback,
-			 * tell scheduler to voluntarily give up the CPU here.
-			 */
-			pr_debug("rescheduling request\n");
-			cond_resched();
-			return -ENOSPC;
+			return pkey_handle_expired();
 		} else if (rc) {
 			hwh_advance(hwh, rc);
 			goto out;
@@ -907,18 +898,8 @@ static int phmac_do_one_request(struct crypto_engine *engine, void *areq)
 		fallthrough;
 	case OP_FINAL:
 		rc = phmac_kmac_final(req, true);
-		if (rc == -EKEYEXPIRED) {
-			/*
-			 * Protected key expired, conversion is in process.
-			 * Trigger a re-schedule of this request by returning
-			 * -ENOSPC ("hardware queue full") to the crypto engine.
-			 * To avoid immediately re-invocation of this callback,
-			 * tell scheduler to voluntarily give up the CPU here.
-			 */
-			pr_debug("rescheduling request\n");
-			cond_resched();
-			return -ENOSPC;
-		}
+		if (rc == -EKEYEXPIRED)
+			return pkey_handle_expired();
 		break;
 	default:
 		/* unknown/unsupported/unimplemented asynch op */
diff --git a/arch/s390/include/asm/pkey.h b/arch/s390/include/asm/pkey.h
index 0af5ac4f646b..9c5f31b50bc8 100644
--- a/arch/s390/include/asm/pkey.h
+++ b/arch/s390/include/asm/pkey.h
@@ -13,6 +13,7 @@
 
 #include <linux/ioctl.h>
 #include <linux/types.h>
+#include <linux/delay.h>
 #include <uapi/asm/pkey.h>
 
 /*
@@ -44,4 +45,20 @@ int pkey_key2protkey(const u8 *key, u32 keylen,
  */
 #define PKEY_XFLAG_NOCLEARKEY 0x0002
 
+static inline int pkey_handle_expired(void)
+{
+	/*
+	 * Protected key expired due to relocation to another
+	 * host. The long runnning re-wrap has no asynchronous
+	 * completion notification, so polling is required.
+	 * Trigger a re-schedule of this request by returning
+	 * -ENOSPC ("hardware queue full") to the crypto engine.
+	 * To avoid immediately re-invocation of this callback,
+	 * tell scheduler to voluntarily give up the CPU here.
+	 */
+	msleep(1);
+	pr_debug("rescheduling request\n");
+	return -ENOSPC;
+}
+
 #endif /* _KAPI_PKEY_H */