test is to be used for benchmarking/validating HPET main counter reading
how to run:
QEMU=/foo/qemu-system-x86_64 x86/run x86/hpet_read_test.flat -smp X
where X is max number of logical CPUs on host
it will 1st execute concurrent read benchmark
and after that it will run torture test enabling/disabling HPET counter,
while running readers in parallel. Goal is to verify counter that always
goes up.
Signed-off-by: Igor Mammedov <imammedo@xxxxxxxxxx>
---
v3:
* measure lat inside threads so that, threads startup time wouldn't
throw off results
* fix BSP iterrupting itself by running read test and stalling
other cpus as result. (fix it by exiting read test earlier if
it's running on BSP)
v2:
* fix broken timer going backwards check
* report # of fails
* warn if number of vcpus is not sufficient for torture test and skip
it
* style fixups
---
x86/Makefile.common | 2 +
x86/hpet_read_test.c | 96 ++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 98 insertions(+)
create mode 100644 x86/hpet_read_test.c
diff --git a/x86/Makefile.common b/x86/Makefile.common
index 5663a65d..ef0e09a6 100644
--- a/x86/Makefile.common
+++ b/x86/Makefile.common
@@ -101,6 +101,8 @@ tests-common += $(TEST_DIR)/realmode.$(exe) \
realmode_bits := $(if $(call cc-option,-m16,""),16,32)
endif
+tests-common += $(TEST_DIR)/hpet_read_test.$(exe)
+
test_cases: $(tests-common) $(tests)
$(TEST_DIR)/%.o: CFLAGS += -std=gnu99 -ffreestanding -I $(SRCDIR)/lib -I $(SRCDIR)/lib/x86 -I lib
diff --git a/x86/hpet_read_test.c b/x86/hpet_read_test.c
new file mode 100644
index 00000000..a4b007ab
--- /dev/null
+++ b/x86/hpet_read_test.c
@@ -0,0 +1,96 @@
+#include "libcflat.h"
+#include "smp.h"
+#include "apic.h"
+#include "asm/barrier.h"
+#include "x86/atomic.h"
+#include "vmalloc.h"
+#include "alloc.h"
+
+#define HPET_ADDR 0xFED00000L
+#define HPET_COUNTER_ADDR ((uint8_t *)HPET_ADDR + 0xF0UL)
+#define HPET_CONFIG_ADDR ((uint8_t *)HPET_ADDR + 0x10UL)
+#define HPET_ENABLE_BIT 0x01UL
+#define HPET_CLK_PERIOD 10
+
+static atomic_t fail;
+static uint64_t *latency;
+
+static void hpet_reader(void *data)
+{
+ uint64_t old_counter = 0, new_counter;
+ long cycles = (long)data;
+
+ /*
+ * on_cpus() will interrupt to run handler as well,
+ * exit without running bench so that on_cpus() would continue spawning
+ * other threads
+ */
+ if (!apic_id())
+ return;
+
+ latency[apic_id()] = *(volatile uint64_t *)HPET_COUNTER_ADDR;
+ while (cycles--) {
+ new_counter = *(volatile uint64_t *)HPET_COUNTER_ADDR;
+ if (new_counter < old_counter)
+ atomic_inc(&fail);
+ old_counter = new_counter;
+ }
+ /* claculate job latency in ns */
+ latency[apic_id()] = (*(volatile uint64_t *)HPET_COUNTER_ADDR - latency[apic_id()])
+ * HPET_CLK_PERIOD
+ /(long)data;
+}
+
+static void hpet_writer(void *data)
+{
+ int i;
+ long cycles = (long)data;
+
+ for (i = 0; i < cycles; ++i)
+ if (i % 2)
+ *(volatile uint64_t *)HPET_CONFIG_ADDR |= HPET_ENABLE_BIT;
+ else
+ *(volatile uint64_t *)HPET_CONFIG_ADDR &= ~HPET_ENABLE_BIT;
+}
+
+int main(void)
+{
+ long cycles = 100000;
+ int i;
+ int ncpus;
+ uint64_t start, end, time_ns, lat = 0;
+
+ ncpus = cpu_count();
+ latency = malloc(sizeof(*latency) * ncpus);
+ do {
+ printf("* starting concurrent read bench on %d cpus\n", ncpus);
+ *(volatile uint64_t *)HPET_CONFIG_ADDR |= HPET_ENABLE_BIT;
+ start = *(volatile uint64_t *)HPET_COUNTER_ADDR;
+ on_cpus(hpet_reader, (void *)cycles);
+ end = (*(volatile uint64_t *)HPET_COUNTER_ADDR);
+ time_ns = (end - start) * HPET_CLK_PERIOD;
+
+ for (i = 1; i < ncpus; i++)
+ lat += latency[i];
+ lat = lat/ncpus;
+
+ report(time_ns && !atomic_read(&fail),
+ "read test took %lu ms, avg read: %lu ns\n", time_ns/1000000, lat);
+ } while (0);
+
+ do {
+ printf("* starting enable/disable with concurrent readers torture\n");
+ if (ncpus > 2) {
+ for (i = 2; i < ncpus; i++)
+ on_cpu_async(i, hpet_reader, (void *)cycles);
+
+ on_cpu(1, hpet_writer, (void *)cycles);
+ report(!atomic_read(&fail), "torture test, fails: %u\n",
+ atomic_read(&fail));
+ } else {
+ printf("SKIP: torture test: '-smp X' should be greater than 2\n");
+ }
+ } while (0);
+
+ return report_summary();
+}
--
2.47.1
