On 04/05/2024 14.28, Nicholas Piggin wrote:
This has a known failure on QEMU TCG machines where the decrementer
interrupt is not lowered when the DEC wraps from -ve to +ve.
Would it then make sense to mark the test with accel = kvm to avoid the test
failure when running with TCG?
diff --git a/powerpc/timebase.c b/powerpc/timebase.c
new file mode 100644
index 000000000..02a4e33c0
--- /dev/null
+++ b/powerpc/timebase.c
@@ -0,0 +1,331 @@
+/* SPDX-License-Identifier: LGPL-2.0-only */
+/*
+ * Test Timebase
+ *
+ * Copyright 2024 Nicholas Piggin, IBM Corp.
+ *
+ * This contains tests of timebase facility, TB, DEC, etc.
+ */
+#include <libcflat.h>
+#include <util.h>
+#include <migrate.h>
+#include <alloc.h>
+#include <asm/handlers.h>
+#include <devicetree.h>
+#include <asm/hcall.h>
+#include <asm/processor.h>
+#include <asm/time.h>
+#include <asm/barrier.h>
+
+static int dec_bits = 0;
+
+static void cpu_dec_bits(int fdtnode, u64 regval __unused, void *arg __unused)
+{
+ const struct fdt_property *prop;
+ int plen;
+
+ prop = fdt_get_property(dt_fdt(), fdtnode, "ibm,dec-bits", &plen);
+ if (!prop) {
+ dec_bits = 32;
+ return;
+ }
+
+ /* Sanity check for the property layout (first two bytes are header) */
+ assert(plen == 4);
+
+ dec_bits = fdt32_to_cpu(*(uint32_t *)prop->data);
+}
+
+/* Check amount of CPUs nodes that have the TM flag */
+static int find_dec_bits(void)
+{
+ int ret;
+
+ ret = dt_for_each_cpu_node(cpu_dec_bits, NULL);
What sense does it make to run this for each CPU node if the cpu_dec_bits
function always overwrites the global dec_bits variable?
Wouldn't it be sufficient to run this for the first node only? Or should the
cpu_dec_bits function maybe check that all nodes have the same value?
+ if (ret < 0)
+ return ret;
+
+ return dec_bits;
+}
+
+
+static bool do_migrate = false;
+static volatile bool got_interrupt;
+static volatile struct pt_regs recorded_regs;
+
+static uint64_t dec_max;
+static uint64_t dec_min;
+
+static void test_tb(int argc, char **argv)
+{
+ uint64_t tb;
+
+ tb = get_tb();
+ if (do_migrate)
+ migrate();
+ report(get_tb() >= tb, "timebase is incrementing");
If you use >= for testing, it could also mean that the TB stays at the same
value, so "timebase is incrementing" sounds misleading. Maybe rather
"timebase is not decreasing" ? Or wait a little bit, then check with ">" only ?
+}
+
+static void dec_stop_handler(struct pt_regs *regs, void *data)
+{
+ mtspr(SPR_DEC, dec_max);
+}
+
+static void dec_handler(struct pt_regs *regs, void *data)
+{
+ got_interrupt = true;
+ memcpy((void *)&recorded_regs, regs, sizeof(struct pt_regs));
+ regs->msr &= ~MSR_EE;
+}
+
+static void test_dec(int argc, char **argv)
+{
+ uint64_t tb1, tb2, dec;
+ int i;
+
+ handle_exception(0x900, &dec_handler, NULL);
+
+ for (i = 0; i < 100; i++) {
+ tb1 = get_tb();
+ mtspr(SPR_DEC, dec_max);
+ dec = mfspr(SPR_DEC);
+ tb2 = get_tb();
+ if (tb2 - tb1 < dec_max - dec)
+ break;
+ }
+ /* POWER CPUs can have a slight (few ticks) variation here */
+ report_kfail(true, tb2 - tb1 >= dec_max - dec, "decrementer remains within TB after mtDEC");
+
+ tb1 = get_tb();
+ mtspr(SPR_DEC, dec_max);
+ mdelay(1000);
+ dec = mfspr(SPR_DEC);
+ tb2 = get_tb();
+ report(tb2 - tb1 >= dec_max - dec, "decrementer remains within TB after 1s");
+
+ mtspr(SPR_DEC, dec_max);
+ local_irq_enable();
+ local_irq_disable();
+ if (mfspr(SPR_DEC) <= dec_max) {
+ report(!got_interrupt, "no interrupt on decrementer positive");
+ }
+ got_interrupt = false;
+
+ mtspr(SPR_DEC, 1);
+ mdelay(100); /* Give the timer a chance to run */
+ if (do_migrate)
+ migrate();
+ local_irq_enable();
+ local_irq_disable();
+ report(got_interrupt, "interrupt on decrementer underflow");
+ got_interrupt = false;
+
+ if (do_migrate)
+ migrate();
+ local_irq_enable();
+ local_irq_disable();
+ report(got_interrupt, "interrupt on decrementer still underflown");
+ got_interrupt = false;
+
+ mtspr(SPR_DEC, 0);
+ mdelay(100); /* Give the timer a chance to run */
+ if (do_migrate)
+ migrate();
+ local_irq_enable();
+ local_irq_disable();
+ report(got_interrupt, "DEC deal with set to 0");
+ got_interrupt = false;
+
+ /* Test for level-triggered decrementer */
+ mtspr(SPR_DEC, -1ULL);
+ if (do_migrate)
+ migrate();
+ local_irq_enable();
+ local_irq_disable();
+ report(got_interrupt, "interrupt on decrementer write MSB");
+ got_interrupt = false;
+
+ mtspr(SPR_DEC, dec_max);
+ local_irq_enable();
+ if (do_migrate)
+ migrate();
+ mtspr(SPR_DEC, -1);
+ local_irq_disable();
+ report(got_interrupt, "interrupt on decrementer write MSB with irqs on");
+ got_interrupt = false;
+
+ mtspr(SPR_DEC, dec_min + 1);
+ mdelay(100);
+ local_irq_enable();
+ local_irq_disable();
+ /* TCG does not model this correctly */
+ report_kfail(true, !got_interrupt, "no interrupt after wrap to positive");
+ got_interrupt = false;
+
+ handle_exception(0x900, NULL, NULL);
+}
+
+static void test_hdec(int argc, char **argv)
+{
+ uint64_t tb1, tb2, hdec;
+
+ if (!machine_is_powernv()) {
+ report_skip("skipping on !powernv machine");
I'd rather say "not running on powernv machine"
+ return;
+ }
Thomas
