kselftest/arm64: Add stress test for SME ZA context switching

Add a stress test for context switching of the ZA register state based on
the similar tests Dave Martin wrote for FPSIMD and SVE registers. The test
loops indefinitely writing a data pattern to ZA then reading it back and
verifying that it's what was expected.

Unlike the other tests we manually assemble the SME instructions since at
present no released toolchain has SME support integrated.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20220419112247.711548-35-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Author: broonie

tools/testing/selftests/arm64/fp/.gitignore

@@ -8,3 +8,4 @@ sve-test
 ssve-test
 vec-syscfg
 vlset
+za-test

tools/testing/selftests/arm64/fp/Makefile

@@ -6,6 +6,7 @@ TEST_PROGS_EXTENDED := fp-pidbench fpsimd-test fpsimd-stress \
 	rdvl-sme rdvl-sve \
 	sve-test sve-stress \
 	ssve-test ssve-stress \
+	za-test za-stress \
 	vlset
 
 all: $(TEST_GEN_PROGS) $(TEST_PROGS_EXTENDED)
@@ -24,5 +25,7 @@ ssve-test: sve-test.S asm-utils.o
 	$(CC) -DSSVE -nostdlib $^ -o $@
 vec-syscfg: vec-syscfg.o rdvl.o
 vlset: vlset.o
+za-test: za-test.o asm-utils.o
+	$(CC) -nostdlib $^ -o $@
 
 include ../../lib.mk

tools/testing/selftests/arm64/fp/za-stress

@@ -0,0 +1,59 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0-only
+# Copyright (C) 2015-2019 ARM Limited.
+# Original author: Dave Martin <Dave.Martin@arm.com>
+
+set -ue
+
+NR_CPUS=`nproc`
+
+pids=
+logs=
+
+cleanup () {
+	trap - INT TERM CHLD
+	set +e
+
+	if [ -n "$pids" ]; then
+		kill $pids
+		wait $pids
+		pids=
+	fi
+
+	if [ -n "$logs" ]; then
+		cat $logs
+		rm $logs
+		logs=
+	fi
+}
+
+interrupt () {
+	cleanup
+	exit 0
+}
+
+child_died () {
+	cleanup
+	exit 1
+}
+
+trap interrupt INT TERM EXIT
+
+for x in `seq 0 $((NR_CPUS * 4))`; do
+	log=`mktemp`
+	logs=$logs\ $log
+	./za-test >$log &
+	pids=$pids\ $!
+done
+
+# Wait for all child processes to be created:
+sleep 10
+
+while :; do
+	kill -USR1 $pids
+done &
+pids=$pids\ $!
+
+wait
+
+exit 1