[kvm-unit-tests PATCH v8 07/10] arm/locking-tests: add comprehensive locking test
Alex Bennée
alex.bennee at linaro.org
Thu Nov 18 10:46:47 PST 2021
This test has been written mainly to stress multi-threaded TCG behaviour
but will demonstrate failure by default on real hardware. The test takes
the following parameters:
- "lock" use GCC's locking semantics
- "atomic" use GCC's __atomic primitives
- "wfelock" use WaitForEvent sleep
- "excl" use load/store exclusive semantics
Also two more options allow the test to be tweaked
- "noshuffle" disables the memory shuffling
- "count=%ld" set your own per-CPU increment count
Signed-off-by: Alex Bennée <alex.bennee at linaro.org>
---
v2
- Don't use thumb style strexeq stuff
- Add atomic and wfelock tests
- Add count/noshuffle test controls
- Move barrier tests to separate test file
v4
- fix up unitests.cfg to use correct test name
- move into "locking" group, remove barrier tests
- use a table to add tests, mark which are expected to work
- correctly report XFAIL
v5
- max out at -smp 4 in unittest.cfg
v7
- make test control flags bools
- default the count to 100000 (so it doesn't timeout)
v8
- rm spinlock test
- fix checkpatch errors
- fix report usage
---
arm/Makefile.common | 2 +-
arm/locking-test.c | 322 ++++++++++++++++++++++++++++++++++++++++++++
arm/spinlock-test.c | 87 ------------
arm/mttcgtests.cfg | 29 ++++
4 files changed, 352 insertions(+), 88 deletions(-)
create mode 100644 arm/locking-test.c
delete mode 100644 arm/spinlock-test.c
diff --git a/arm/Makefile.common b/arm/Makefile.common
index e3f04f2..f905971 100644
--- a/arm/Makefile.common
+++ b/arm/Makefile.common
@@ -5,7 +5,6 @@
#
tests-common = $(TEST_DIR)/selftest.flat
-tests-common += $(TEST_DIR)/spinlock-test.flat
tests-common += $(TEST_DIR)/pci-test.flat
tests-common += $(TEST_DIR)/pmu.flat
tests-common += $(TEST_DIR)/gic.flat
@@ -13,6 +12,7 @@ tests-common += $(TEST_DIR)/psci.flat
tests-common += $(TEST_DIR)/sieve.flat
tests-common += $(TEST_DIR)/pl031.flat
tests-common += $(TEST_DIR)/tlbflush-code.flat
+tests-common += $(TEST_DIR)/locking-test.flat
tests-all = $(tests-common) $(tests)
all: directories $(tests-all)
diff --git a/arm/locking-test.c b/arm/locking-test.c
new file mode 100644
index 0000000..eab9497
--- /dev/null
+++ b/arm/locking-test.c
@@ -0,0 +1,322 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Locking Test
+ *
+ * This test allows us to stress the various atomic primitives of a VM
+ * guest. A number of methods are available that use various patterns
+ * to implement a lock.
+ *
+ * Copyright (C) 2017 Linaro
+ * Author: Alex Bennée <alex.bennee at linaro.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <libcflat.h>
+#include <asm/smp.h>
+#include <asm/cpumask.h>
+#include <asm/barrier.h>
+#include <asm/mmu.h>
+
+#include <prng.h>
+
+#define MAX_CPUS 8
+
+/* Test definition structure
+ *
+ * A simple structure that describes the test name, expected pass and
+ * increment function.
+ */
+
+/* Function pointers for test */
+typedef void (*inc_fn)(int cpu);
+
+typedef struct {
+ const char *test_name;
+ bool should_pass;
+ inc_fn main_fn;
+} test_descr_t;
+
+/* How many increments to do */
+static int increment_count = 1000000;
+static bool do_shuffle = true;
+
+/* Shared value all the tests attempt to safely increment using
+ * various forms of atomic locking and exclusive behaviour.
+ */
+static unsigned int shared_value;
+
+/* PAGE_SIZE * uint32_t means we span several pages */
+__attribute__((aligned(PAGE_SIZE))) static uint32_t memory_array[PAGE_SIZE];
+
+/* We use the alignment of the following to ensure accesses to locking
+ * and synchronisation primatives don't interfere with the page of the
+ * shared value
+ */
+__attribute__((aligned(PAGE_SIZE))) static unsigned int per_cpu_value[MAX_CPUS];
+__attribute__((aligned(PAGE_SIZE))) static cpumask_t smp_test_complete;
+__attribute__((aligned(PAGE_SIZE))) struct isaac_ctx prng_context[MAX_CPUS];
+
+/* Some of the approaches use a global lock to prevent contention. */
+static int global_lock;
+
+/* In any SMP setting this *should* fail due to cores stepping on
+ * each other updating the shared variable
+ */
+static void increment_shared(int cpu)
+{
+ (void)cpu;
+
+ shared_value++;
+}
+
+/* GCC __sync primitives are deprecated in favour of __atomic */
+static void increment_shared_with_lock(int cpu)
+{
+ (void)cpu;
+
+ while (__sync_lock_test_and_set(&global_lock, 1));
+
+ shared_value++;
+
+ __sync_lock_release(&global_lock);
+}
+
+/*
+ * In practice even __ATOMIC_RELAXED uses ARM's ldxr/stex exclusive
+ * semantics
+ */
+static void increment_shared_with_atomic(int cpu)
+{
+ (void)cpu;
+
+ __atomic_add_fetch(&shared_value, 1, __ATOMIC_SEQ_CST);
+}
+
+
+/*
+ * Load/store exclusive with WFE (wait-for-event)
+ *
+ * See ARMv8 ARM examples:
+ * Use of Wait For Event (WFE) and Send Event (SEV) with locks
+ */
+
+static void increment_shared_with_wfelock(int cpu)
+{
+ (void)cpu;
+
+#if defined(__aarch64__)
+ asm volatile(
+ " mov w1, #1\n"
+ " sevl\n"
+ " prfm PSTL1KEEP, [%[lock]]\n"
+ "1: wfe\n"
+ " ldaxr w0, [%[lock]]\n"
+ " cbnz w0, 1b\n"
+ " stxr w0, w1, [%[lock]]\n"
+ " cbnz w0, 1b\n"
+ /* lock held */
+ " ldr w0, [%[sptr]]\n"
+ " add w0, w0, #0x1\n"
+ " str w0, [%[sptr]]\n"
+ /* now release */
+ " stlr wzr, [%[lock]]\n"
+ : /* out */
+ : [lock] "r" (&global_lock), [sptr] "r" (&shared_value) /* in */
+ : "w0", "w1", "cc");
+#else
+ asm volatile(
+ " mov r1, #1\n"
+ "1: ldrex r0, [%[lock]]\n"
+ " cmp r0, #0\n"
+ " wfene\n"
+ " strexeq r0, r1, [%[lock]]\n"
+ " cmpeq r0, #0\n"
+ " bne 1b\n"
+ " dmb\n"
+ /* lock held */
+ " ldr r0, [%[sptr]]\n"
+ " add r0, r0, #0x1\n"
+ " str r0, [%[sptr]]\n"
+ /* now release */
+ " mov r0, #0\n"
+ " dmb\n"
+ " str r0, [%[lock]]\n"
+ " dsb\n"
+ " sev\n"
+ : /* out */
+ : [lock] "r" (&global_lock), [sptr] "r" (&shared_value) /* in */
+ : "r0", "r1", "cc");
+#endif
+}
+
+
+/*
+ * Hand-written version of the load/store exclusive
+ */
+static void increment_shared_with_excl(int cpu)
+{
+ (void)cpu;
+
+#if defined(__aarch64__)
+ asm volatile(
+ "1: ldxr w0, [%[sptr]]\n"
+ " add w0, w0, #0x1\n"
+ " stxr w1, w0, [%[sptr]]\n"
+ " cbnz w1, 1b\n"
+ : /* out */
+ : [sptr] "r" (&shared_value) /* in */
+ : "w0", "w1", "cc");
+#else
+ asm volatile(
+ "1: ldrex r0, [%[sptr]]\n"
+ " add r0, r0, #0x1\n"
+ " strex r1, r0, [%[sptr]]\n"
+ " cmp r1, #0\n"
+ " bne 1b\n"
+ : /* out */
+ : [sptr] "r" (&shared_value) /* in */
+ : "r0", "r1", "cc");
+#endif
+}
+
+/* Test array */
+static test_descr_t tests[] = {
+ { "none", false, increment_shared },
+ { "lock", true, increment_shared_with_lock },
+ { "atomic", true, increment_shared_with_atomic },
+ { "wfelock", true, increment_shared_with_wfelock },
+ { "excl", true, increment_shared_with_excl }
+};
+
+/* The idea of this is just to generate some random load/store
+ * activity which may or may not race with an un-barried incremented
+ * of the shared counter
+ */
+static void shuffle_memory(int cpu)
+{
+ int i;
+ uint32_t lspat = isaac_next_uint32(&prng_context[cpu]);
+ uint32_t seq = isaac_next_uint32(&prng_context[cpu]);
+ int count = seq & 0x1f;
+ uint32_t val = 0;
+
+ seq >>= 5;
+
+ for (i = 0; i < count; i++) {
+ int index = seq & ~PAGE_MASK;
+
+ if (lspat & 1)
+ val ^= memory_array[index];
+ else
+ memory_array[index] = val;
+
+ seq >>= PAGE_SHIFT;
+ seq ^= lspat;
+ lspat >>= 1;
+ }
+
+}
+
+static inc_fn increment_function;
+
+static void do_increment(void)
+{
+ int i;
+ int cpu = smp_processor_id();
+
+ printf("CPU%d: online and ++ing\n", cpu);
+
+ for (i = 0; i < increment_count; i++) {
+ per_cpu_value[cpu]++;
+ increment_function(cpu);
+
+ if (do_shuffle)
+ shuffle_memory(cpu);
+ }
+
+ printf("CPU%d: Done, %d incs\n", cpu, per_cpu_value[cpu]);
+
+ cpumask_set_cpu(cpu, &smp_test_complete);
+ if (cpu != 0)
+ halt();
+}
+
+static void setup_and_run_test(test_descr_t *test)
+{
+ unsigned int i, sum = 0;
+ int cpu, cpu_cnt = 0;
+
+ increment_function = test->main_fn;
+
+ /* fill our random page */
+ for (i = 0; i < PAGE_SIZE; i++)
+ memory_array[i] = isaac_next_uint32(&prng_context[0]);
+
+ for_each_present_cpu(cpu) {
+ uint32_t seed2 = isaac_next_uint32(&prng_context[0]);
+
+ cpu_cnt++;
+ if (cpu == 0)
+ continue;
+
+ isaac_init(&prng_context[cpu], (unsigned char *) &seed2, sizeof(seed2));
+ smp_boot_secondary(cpu, do_increment);
+ }
+
+ do_increment();
+
+ while (!cpumask_full(&smp_test_complete))
+ cpu_relax();
+
+ /* All CPUs done, do we add up */
+ for_each_present_cpu(cpu) {
+ sum += per_cpu_value[cpu];
+ }
+
+ if (test->should_pass)
+ report(sum == shared_value, "total incs %d", shared_value);
+ else
+ report_xfail(true, sum == shared_value, "total incs %d", shared_value);
+}
+
+int main(int argc, char **argv)
+{
+ static const unsigned char seed[] = "myseed";
+ test_descr_t *test = &tests[0];
+ int i;
+ unsigned int j;
+
+ isaac_init(&prng_context[0], &seed[0], sizeof(seed));
+
+ for (i = 0; i < argc; i++) {
+ char *arg = argv[i];
+
+ /* Check for test name */
+ for (j = 0; j < ARRAY_SIZE(tests); j++) {
+ if (strcmp(arg, tests[j].test_name) == 0)
+ test = &tests[j];
+ }
+
+ /* Test modifiers */
+ if (strcmp(arg, "noshuffle") == 0) {
+ do_shuffle = false;
+ report_prefix_push("noshuffle");
+ } else if (strstr(arg, "count=") != NULL) {
+ char *p = strstr(arg, "=");
+
+ increment_count = atol(p+1);
+ } else {
+ isaac_reseed(&prng_context[0], (unsigned char *) arg, strlen(arg));
+ }
+ }
+
+ if (test)
+ setup_and_run_test(test);
+ else
+ report(false, "Unknown test");
+
+ return report_summary();
+}
diff --git a/arm/spinlock-test.c b/arm/spinlock-test.c
deleted file mode 100644
index 73aea76..0000000
--- a/arm/spinlock-test.c
+++ /dev/null
@@ -1,87 +0,0 @@
-/*
- * Spinlock test
- *
- * This code is based on code from the tcg_baremetal_tests.
- *
- * Copyright (C) 2015 Virtual Open Systems SAS
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- */
-
-#include <libcflat.h>
-#include <asm/smp.h>
-#include <asm/barrier.h>
-
-#define LOOP_SIZE 10000000
-
-struct lock_ops {
- void (*lock)(int *v);
- void (*unlock)(int *v);
-};
-static struct lock_ops lock_ops;
-
-static void gcc_builtin_lock(int *lock_var)
-{
- while (__sync_lock_test_and_set(lock_var, 1));
-}
-static void gcc_builtin_unlock(int *lock_var)
-{
- __sync_lock_release(lock_var);
-}
-static void none_lock(int *lock_var)
-{
- while (*(volatile int *)lock_var != 0);
- *(volatile int *)lock_var = 1;
-}
-static void none_unlock(int *lock_var)
-{
- *(volatile int *)lock_var = 0;
-}
-
-static int global_a, global_b;
-static int global_lock;
-
-static void test_spinlock(void *data __unused)
-{
- int i, errors = 0;
- int cpu = smp_processor_id();
-
- printf("CPU%d online\n", cpu);
-
- for (i = 0; i < LOOP_SIZE; i++) {
-
- lock_ops.lock(&global_lock);
-
- if (global_a == (cpu + 1) % 2) {
- global_a = 1;
- global_b = 0;
- } else {
- global_a = 0;
- global_b = 1;
- }
-
- if (global_a == global_b)
- errors++;
-
- lock_ops.unlock(&global_lock);
- }
- report(errors == 0, "CPU%d: Done - Errors: %d", cpu, errors);
-}
-
-int main(int argc, char **argv)
-{
- report_prefix_push("spinlock");
- if (argc > 1 && strcmp(argv[1], "bad") != 0) {
- lock_ops.lock = gcc_builtin_lock;
- lock_ops.unlock = gcc_builtin_unlock;
- } else {
- lock_ops.lock = none_lock;
- lock_ops.unlock = none_unlock;
- }
-
- on_cpus(test_spinlock, NULL);
-
- return report_summary();
-}
diff --git a/arm/mttcgtests.cfg b/arm/mttcgtests.cfg
index d3ff102..46fcb57 100644
--- a/arm/mttcgtests.cfg
+++ b/arm/mttcgtests.cfg
@@ -28,3 +28,32 @@ file = tlbflush-code.flat
smp = $(($MAX_SMP>4?4:$MAX_SMP))
extra_params = -append 'page self'
+# Locking tests
+[locking::none]
+file = locking-test.flat
+smp = $(($MAX_SMP>4?4:$MAX_SMP))
+groups = locking
+
+[locking::lock]
+file = locking-test.flat
+smp = $(($MAX_SMP>4?4:$MAX_SMP))
+extra_params = -append 'lock'
+groups = locking
+
+[locking::atomic]
+file = locking-test.flat
+smp = $(($MAX_SMP>4?4:$MAX_SMP))
+extra_params = -append 'atomic'
+groups = locking
+
+[locking::wfelock]
+file = locking-test.flat
+smp = $(($MAX_SMP>4?4:$MAX_SMP))
+extra_params = -append 'wfelock'
+groups = locking
+
+[locking::excl]
+file = locking-test.flat
+smp = $(($MAX_SMP>4?4:$MAX_SMP))
+extra_params = -append 'excl'
+groups = locking
--
2.30.2
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