Linux 4.14, 4.19, 5.0+ compat: SIMD save/restore

Contrary to initial testing we cannot rely on these kernels to
invalidate the per-cpu FPU state and restore the FPU registers.
Nor can we guarantee that the kernel won't modify the FPU state
which we saved in the task struck.

Therefore, the kfpu_begin() and kfpu_end() functions have been
updated to save and restore the FPU state using our own dedicated
per-cpu FPU state variables.

This has the additional advantage of allowing us to use the FPU
again in user threads.  So we remove the code which was added to
use task queues to ensure some functions ran in kernel threads.

Reviewed-by: Fabian Grünbichler <[email protected]>
Reviewed-by: Tony Hutter <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Issue #9346
Closes #9403 

1 files changed, 3 insertions, 29 deletions

diff --git a/module/icp/io/aes.c b/module/icp/io/aes.c
index 4b2dbd6e1..788bcef7d 100644
--- a/module/icp/io/aes.c
+++ b/module/icp/io/aes.c
@@ -206,35 +206,9 @@ aes_mod_init(void)
 {
 	int ret;
 
-#if defined(_KERNEL)
-	/*
-	 * Determine the fastest available implementation.  The benchmarks
-	 * are run in dedicated kernel threads to allow Linux 5.0+ kernels
-	 * to use SIMD operations.  If for some reason this isn't possible,
-	 * fallback to the generic implementations.  See the comment in
-	 * linux/simd_x86.h for additional details.  Additionally, this has
-	 * the benefit of allowing them to be run in parallel.
-	 */
-	taskqid_t aes_id = taskq_dispatch(system_taskq, aes_impl_init,
-	    NULL, TQ_SLEEP);
-	taskqid_t gcm_id = taskq_dispatch(system_taskq, gcm_impl_init,
-	    NULL, TQ_SLEEP);
-
-	if (aes_id != TASKQID_INVALID) {
-		taskq_wait_id(system_taskq, aes_id);
-	} else {
-		aes_impl_init(NULL);
-	}
-
-	if (gcm_id != TASKQID_INVALID) {
-		taskq_wait_id(system_taskq, gcm_id);
-	} else {
-		gcm_impl_init(NULL);
-	}
-#else
-	aes_impl_init(NULL);
-	gcm_impl_init(NULL);
-#endif
+	/* Determine the fastest available implementation. */
+	aes_impl_init();
+	gcm_impl_init();
 
 	if ((ret = mod_install(&modlinkage)) != 0)
 		return (ret);