crypto: drbg - Align buffers to at least a cache line

None of the ciphers used by the DRBG have an alignment requirement; thus,
they all return 0 from .crypto_init, resulting in inconsistent alignment
across all buffers.

Align all buffers to at least a cache line to improve performance. This is
especially useful when multiple DRBG instances are used, since it prevents
false sharing of cache lines between the different instances.

Signed-off-by: Sultan Alsawaf <[email protected]>

Author: kerneltoast

crypto/drbg.c

@@ -1283,6 +1283,12 @@ static inline int drbg_alloc_state(struct drbg_state *drbg)
 	if (ret < 0)
 		goto err;
 
+	/*
+	 * Align to at least a cache line for better performance. This also
+	 * prevents false sharing of cache lines between different instances.
+	 */
+	ret = max(ret, L1_CACHE_BYTES - 1);
+
 	drbg->Vbuf = kmalloc(drbg_statelen(drbg) + ret, GFP_KERNEL);
 	if (!drbg->Vbuf) {
 		ret = -ENOMEM;