[Qemu-devel] [RFC 08/11] arm/tlbflush-test: Add TLB torture 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 <address@hidden>

---
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
---
 arm/tlbflush-test.c          | 194 +++++++++++++++++++++++++++++++++++++++++++
 arm/unittests.cfg            |  24 ++++++
 config/config-arm-common.mak |   2 +
 3 files changed, 220 insertions(+)
 create mode 100644 arm/tlbflush-test.c

diff --git a/arm/tlbflush-test.c b/arm/tlbflush-test.c
new file mode 100644
index 0000000..0375ad9
--- /dev/null
+++ b/arm/tlbflush-test.c
@@ -0,0 +1,194 @@
+#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 int flush_self = 0;
+static int flush_page = 0;
+static int flush_verbose = 0;
+
+/* 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%x!=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 = 1;
+                }
+
+                if (strcmp(arg, "self") == 0) {
+                       flush_self = 1;
+                }
+
+               if (strcmp(arg, "verbose") == 0) {
+                       flush_verbose = 1;
+                }
+       }
+
+       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 5e26da1..8aebdba 100644
--- a/arm/unittests.cfg
+++ b/arm/unittests.cfg
@@ -38,3 +38,27 @@ file = selftest.flat
 smp = $MAX_SMP
 extra_params = -append 'smp'
 groups = selftest
+
+# TLB Torture Tests
+[tlbflush::all_other]
+file = tlbflush-test.flat
+smp = $MAX_SMP
+groups = tlbflush
+
+[tlbflush::page_other]
+file = tlbflush-test.flat
+smp = $MAX_SMP
+extra_params = -append 'page'
+groups = tlbflush
+
+[tlbflush::all_self]
+file = tlbflush-test.flat
+smp = $MAX_SMP
+extra_params = -append 'self'
+groups = tlbflush
+
+[tlbflush::page_self]
+file = tlbflush-test.flat
+smp = $MAX_SMP
+extra_params = -append 'page self'
+groups = tlbflush
diff --git a/config/config-arm-common.mak b/config/config-arm-common.mak
index 732c805..e6ad11b 100644
--- a/config/config-arm-common.mak
+++ b/config/config-arm-common.mak
@@ -12,6 +12,7 @@ endif
 tests-common = $(TEST_DIR)/selftest.flat
 tests-common += $(TEST_DIR)/spinlock-test.flat
 tests-common += $(TEST_DIR)/ipi-test.flat
+tests-common += $(TEST_DIR)/tlbflush-test.flat
 
 all: test_cases
 
@@ -72,3 +73,4 @@ test_cases: $(generated_files) $(tests-common) $(tests)
 $(TEST_DIR)/selftest.elf: $(cstart.o) $(TEST_DIR)/selftest.o
 $(TEST_DIR)/spinlock-test.elf: $(cstart.o) $(TEST_DIR)/spinlock-test.o
 $(TEST_DIR)/ipi-test.elf: $(cstart.o) $(TEST_DIR)/ipi-test.o
+$(TEST_DIR)/tlbflush-test.elf: $(cstart.o) $(TEST_DIR)/tlbflush-test.o
-- 
2.7.1