[kvm-unit-tests PATCH v7 07/11] arm/tlbflush-code: Add TLB flush during code execution test

[Alex Bennée]

This adds a fairly brain dead torture test for TLB flushes intended for
stressing the MTTCG QEMU build. It takes the usual -smp option for
multiple CPUs.

By default it CPU0 will do a TLBIALL flush after each cycle. You can
pass options via -append to control additional aspects of the test:

  - "page" flush each page in turn (one per function)
  - "self" do the flush after each computation cycle
  - "verbose" report progress on each computation cycle

Signed-off-by: Alex Bennée <alex.bennee at linaro.org>
CC: Mark Rutland <mark.rutland at arm.com>

---
v2
  - rename to tlbflush-test
  - made makefile changes cleaner
  - added self/other flush mode
  - create specific prefix
  - whitespace fixes
v3
  - using new SMP framework for test runing
v4
  - merge in the unitests.cfg
v5
  - max out at -smp 4
  - printf fmtfix
v7
  - rename to tlbflush-code
  - int -> bool flags
---
 arm/Makefile.common |   2 +
 arm/tlbflush-code.c | 212 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 arm/unittests.cfg   |  24 ++++++
 3 files changed, 238 insertions(+)
 create mode 100644 arm/tlbflush-code.c

diff --git a/arm/Makefile.common b/arm/Makefile.common
index cca0d9c..de99a6e 100644
--- a/arm/Makefile.common
+++ b/arm/Makefile.common
@@ -13,6 +13,7 @@ tests-common  = $(TEST_DIR)/selftest.flat
 tests-common += $(TEST_DIR)/spinlock-test.flat
 tests-common += $(TEST_DIR)/pci-test.flat
 tests-common += $(TEST_DIR)/gic.flat
+tests-common += $(TEST_DIR)/tlbflush-code.flat
 
 all: test_cases
 
@@ -81,3 +82,4 @@ generated_files = $(asm-offsets)
 test_cases: $(generated_files) $(tests-common) $(tests)
 
 $(TEST_DIR)/selftest.o $(cstart.o): $(asm-offsets)
+$(TEST_DIR)/tlbflush-code.elf: $(cstart.o) $(TEST_DIR)/tlbflush-code.o
diff --git a/arm/tlbflush-code.c b/arm/tlbflush-code.c
new file mode 100644
index 0000000..cb5cdc2
--- /dev/null
+++ b/arm/tlbflush-code.c
@@ -0,0 +1,212 @@
+/*
+ * TLB Flush Race Tests
+ *
+ * These tests are designed to test for incorrect TLB flush semantics
+ * under emulation. The initial CPU will set all the others working a
+ * compuation task and will then trigger TLB flushes across the
+ * system. It doesn't actually need to re-map anything but the flushes
+ * themselves will trigger QEMU's TCG self-modifying code detection
+ * which will invalidate any generated  code causing re-translation.
+ * Eventually the code buffer will fill and a general tb_lush() will
+ * be triggered.
+ *
+ * Copyright (C) 2016, Linaro, Alex Bennée <alex.bennee at linaro.org>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2.
+ */
+
+#include <libcflat.h>
+#include <asm/smp.h>
+#include <asm/cpumask.h>
+#include <asm/barrier.h>
+#include <asm/mmu.h>
+
+#define SEQ_LENGTH 10
+#define SEQ_HASH 0x7cd707fe
+
+static cpumask_t smp_test_complete;
+static int flush_count = 1000000;
+static bool flush_self;
+static bool flush_page;
+static bool flush_verbose;
+
+/*
+ * Work functions
+ *
+ * These work functions need to be:
+ *
+ *  - page aligned, so we can flush one function at a time
+ *  - have branches, so QEMU TCG generates multiple basic blocks
+ *  - call across pages, so we exercise the TCG basic block slow path
+ */
+
+/* Adler32 */
+__attribute__((aligned(PAGE_SIZE))) uint32_t hash_array(const void *buf,
+							size_t buflen)
+{
+	const uint8_t *data = (uint8_t *) buf;
+	uint32_t s1 = 1;
+	uint32_t s2 = 0;
+
+	for (size_t n = 0; n < buflen; n++) {
+		s1 = (s1 + data[n]) % 65521;
+		s2 = (s2 + s1) % 65521;
+	}
+	return (s2 << 16) | s1;
+}
+
+__attribute__((aligned(PAGE_SIZE))) void create_fib_sequence(int length,
+							unsigned int *array)
+{
+	int i;
+
+	/* first two values */
+	array[0] = 0;
+	array[1] = 1;
+	for (i=2; i<length; i++) {
+		array[i] = array[i-2] + array[i-1];
+	}
+}
+
+__attribute__((aligned(PAGE_SIZE))) unsigned long long factorial(unsigned int n)
+{
+	unsigned int i;
+	unsigned long long fac = 1;
+	for (i=1; i<=n; i++)
+	{
+		fac = fac * i;
+	}
+	return fac;
+}
+
+__attribute__((aligned(PAGE_SIZE))) void factorial_array
+(unsigned int n, unsigned int *input, unsigned long long *output)
+{
+	unsigned int i;
+	for (i=0; i<n; i++) {
+		output[i] = factorial(input[i]);
+	}
+}
+
+__attribute__((aligned(PAGE_SIZE))) unsigned int do_computation(void)
+{
+	unsigned int fib_array[SEQ_LENGTH];
+	unsigned long long facfib_array[SEQ_LENGTH];
+	uint32_t fib_hash, facfib_hash;
+
+	create_fib_sequence(SEQ_LENGTH, &fib_array[0]);
+	fib_hash = hash_array(&fib_array[0], sizeof(fib_array));
+	factorial_array(SEQ_LENGTH, &fib_array[0], &facfib_array[0]);
+	facfib_hash = hash_array(&facfib_array[0], sizeof(facfib_array));
+
+	return (fib_hash ^ facfib_hash);
+}
+
+/* This provides a table of the work functions so we can flush each
+ * page individually
+ */
+static void * pages[] = {&hash_array, &create_fib_sequence, &factorial,
+			 &factorial_array, &do_computation};
+
+static void do_flush(int i)
+{
+	if (flush_page) {
+		flush_tlb_page((unsigned long)pages[i % ARRAY_SIZE(pages)]);
+	} else {
+		flush_tlb_all();
+	}
+}
+
+
+static void just_compute(void)
+{
+	int i, errors = 0;
+	int cpu = smp_processor_id();
+
+	uint32_t result;
+
+	printf("CPU%d online\n", cpu);
+
+	for (i=0; i < flush_count; i++) {
+		result = do_computation();
+
+		if (result != SEQ_HASH) {
+			errors++;
+			printf("CPU%d: seq%d 0x%"PRIx32"!=0x%x\n",
+				cpu, i, result, SEQ_HASH);
+		}
+
+		if (flush_verbose && (i % 1000) == 0) {
+			printf("CPU%d: seq%d\n", cpu, i);
+		}
+
+		if (flush_self) {
+			do_flush(i);
+		}
+	}
+
+	report("CPU%d: Done - Errors: %d\n", errors == 0, cpu, errors);
+
+	cpumask_set_cpu(cpu, &smp_test_complete);
+	if (cpu != 0)
+		halt();
+}
+
+static void just_flush(void)
+{
+	int cpu = smp_processor_id();
+	int i = 0;
+
+	/* set our CPU as done, keep flushing until everyone else
+	   finished */
+	cpumask_set_cpu(cpu, &smp_test_complete);
+
+	while (!cpumask_full(&smp_test_complete)) {
+		do_flush(i++);
+	}
+
+	report("CPU%d: Done - Triggered %d flushes\n", true, cpu, i);
+}
+
+int main(int argc, char **argv)
+{
+	int cpu, i;
+	char prefix[100];
+
+	for (i=0; i<argc; i++) {
+		char *arg = argv[i];
+
+		if (strcmp(arg, "page") == 0) {
+			flush_page = true;
+                }
+
+                if (strcmp(arg, "self") == 0) {
+			flush_self = true;
+                }
+
+		if (strcmp(arg, "verbose") == 0) {
+			flush_verbose = true;
+                }
+	}
+
+	snprintf(prefix, sizeof(prefix), "tlbflush_%s_%s",
+		flush_page?"page":"all",
+		flush_self?"self":"other");
+	report_prefix_push(prefix);
+
+	for_each_present_cpu(cpu) {
+		if (cpu == 0)
+			continue;
+		smp_boot_secondary(cpu, just_compute);
+	}
+
+	if (flush_self)
+		just_compute();
+	else
+		just_flush();
+
+	while (!cpumask_full(&smp_test_complete))
+		cpu_relax();
+
+	return report_summary();
+}
diff --git a/arm/unittests.cfg b/arm/unittests.cfg
index c7392c7..beaae84 100644
--- a/arm/unittests.cfg
+++ b/arm/unittests.cfg
@@ -72,3 +72,27 @@ file = gic.flat
 smp = $MAX_SMP
 extra_params = -machine gic-version=3 -append 'ipi'
 groups = gic
+
+# TLB Torture Tests
+[tlbflush-code::all_other]
+file = tlbflush-code.flat
+smp = $(($MAX_SMP>4?4:$MAX_SMP))
+groups = tlbflush
+
+[tlbflush-code::page_other]
+file = tlbflush-code.flat
+smp = $(($MAX_SMP>4?4:$MAX_SMP))
+extra_params = -append 'page'
+groups = tlbflush
+
+[tlbflush-code::all_self]
+file = tlbflush-code.flat
+smp = $(($MAX_SMP>4?4:$MAX_SMP))
+extra_params = -append 'self'
+groups = tlbflush
+
+[tlbflush-code::page_self]
+file = tlbflush-code.flat
+smp = $(($MAX_SMP>4?4:$MAX_SMP))
+extra_params = -append 'page self'
+groups = tlbflush
-- 
2.10.1