[kvm-unit-tests PATCH 1/2] x86/apic: separate reporting from actual measurements

[Igor Mammedov <imammedo@redhat.com>]

Move report() calls to the end of the function so that serial I/O
does not interfere with timer measurements.

While at it, wrap the test body in a for loop as preparation
for adding retry logic to deal with failures due to large
enough vCPU stalls.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
 x86/apic.c | 109 +++++++++++++++++++++++++++++++----------------------
 1 file changed, 63 insertions(+), 46 deletions(-)

diff --git a/x86/apic.c b/x86/apic.c
index 0a52e9a4..d4eb8e11 100644
--- a/x86/apic.c
+++ b/x86/apic.c
@@ -573,62 +573,79 @@ static inline void apic_change_mode(unsigned long new_mode)
 
 static void test_apic_change_mode(void)
 {
-	uint32_t tmict = 0x999999;
+	const uint32_t tmict_values[] = {
+		0x999999,    /* ~10ms */
+	};
+	int retry, max_retries = ARRAY_SIZE(tmict_values);
+	uint32_t tmict;
+	bool tmict_reset = false, o_nonzero = false, o_reached_zero = false;
+	bool p_nonzero = false, p_not_reset = false, p_after_wrap = false;
+	bool p2o_not_reset = false, p2o_reached_zero = false, p2o_stay_zero = false;
 
 	printf("starting apic change mode\n");
 
-	apic_write(APIC_TMICT, tmict);
+	for (retry = 0; retry < max_retries; retry++) {
+		tmict = tmict_values[retry];
+		apic_write(APIC_TMICT, tmict);
+		apic_change_mode(APIC_LVT_TIMER_PERIODIC);
+		tmict_reset = apic_read(APIC_TMICT) == tmict;
 
-	apic_change_mode(APIC_LVT_TIMER_PERIODIC);
+		/* Testing one-shot */
+		apic_change_mode(APIC_LVT_TIMER_ONESHOT);
+		apic_write(APIC_TMICT, tmict);
+		o_nonzero = apic_read(APIC_TMCCT);
 
-	report(apic_read(APIC_TMICT) == tmict, "TMICT value reset");
+		wait_until_tmcct_is_zero(tmict, false);
+		o_reached_zero = !apic_read(APIC_TMCCT);
 
-	/* Testing one-shot */
-	apic_change_mode(APIC_LVT_TIMER_ONESHOT);
-	apic_write(APIC_TMICT, tmict);
-	report(apic_read(APIC_TMCCT), "TMCCT should have a non-zero value");
+		/*
+		 * Write TMICT before changing mode from one-shot to periodic
+		 * TMCCT should be reset to TMICT periodicly
+		 */
+		apic_write(APIC_TMICT, tmict);
+		wait_until_tmcct_is_zero(tmict, true);
+		apic_change_mode(APIC_LVT_TIMER_PERIODIC);
+		p_nonzero = apic_read(APIC_TMCCT);
 
-	wait_until_tmcct_is_zero(tmict, false);
-	report(!apic_read(APIC_TMCCT), "TMCCT should have reached 0");
+		/*
+		 * After the change of mode, the counter should not be reset
+		 * and continue counting down from where it was
+		 */
+		p_not_reset = apic_read(APIC_TMCCT) < (tmict / 2);
+		/*
+		 * Specifically wait for timer wrap around and skip 0.
+		 * Under KVM lapic there is a possibility that a small amount
+		 * of consecutive TMCCR reads return 0 while hrtimer is reset
+		 * in an async callback
+		 */
+		wait_until_tmcct_wrap_around(tmict, false);
+		p_after_wrap = apic_read(APIC_TMCCT) > (tmict / 2);
 
-	/*
-	 * Write TMICT before changing mode from one-shot to periodic TMCCT should
-	 * be reset to TMICT periodicly
-	 */
-	apic_write(APIC_TMICT, tmict);
-	wait_until_tmcct_is_zero(tmict, true);
-	apic_change_mode(APIC_LVT_TIMER_PERIODIC);
-	report(apic_read(APIC_TMCCT), "TMCCT should have a non-zero value");
+		wait_until_tmcct_is_zero(tmict, true);
+		/*
+		 * Keep the same TMICT and change timer mode to one-shot
+		 * TMCCT should be > 0 and count-down to 0
+		 */
+		apic_change_mode(APIC_LVT_TIMER_ONESHOT);
+		p2o_not_reset = apic_read(APIC_TMCCT) < (tmict / 2);
 
-	/*
-	 * After the change of mode, the counter should not be reset and continue
-	 * counting down from where it was
-	 */
-	report(apic_read(APIC_TMCCT) < (tmict / 2),
-	       "TMCCT should not be reset to TMICT value");
-	/*
-	 * Specifically wait for timer wrap around and skip 0.
-	 * Under KVM lapic there is a possibility that a small amount of consecutive
-	 * TMCCR reads return 0 while hrtimer is reset in an async callback
-	 */
-	wait_until_tmcct_wrap_around(tmict, false);
-	report(apic_read(APIC_TMCCT) > (tmict / 2),
-	       "TMCCT should be reset to the initial-count");
+		wait_until_tmcct_is_zero(tmict, false);
+		p2o_reached_zero = !apic_read(APIC_TMCCT);
 
-	wait_until_tmcct_is_zero(tmict, true);
-	/*
-	 * Keep the same TMICT and change timer mode to one-shot
-	 * TMCCT should be > 0 and count-down to 0
-	 */
-	apic_change_mode(APIC_LVT_TIMER_ONESHOT);
-	report(apic_read(APIC_TMCCT) < (tmict / 2),
-	       "TMCCT should not be reset to init");
-	wait_until_tmcct_is_zero(tmict, false);
-	report(!apic_read(APIC_TMCCT), "TMCCT should have reach zero");
-
-	/* now tmcct == 0 and tmict != 0 */
-	apic_change_mode(APIC_LVT_TIMER_PERIODIC);
-	report(!apic_read(APIC_TMCCT), "TMCCT should stay at zero");
+		/* now tmcct == 0 and tmict != 0 */
+		apic_change_mode(APIC_LVT_TIMER_PERIODIC);
+		p2o_stay_zero = !apic_read(APIC_TMCCT);
+	}
+
+	report(tmict_reset, "TMICT value reset");
+	report(o_nonzero, "one-shot: TMCCT should have a non-zero value");
+	report(o_reached_zero, "one-shot: TMCCT should have reached 0");
+	report(p_nonzero, "periodic: TMCCT should have a non-zero value");
+	report(p_not_reset, "TMCCT should not be reset to TMICT value");
+	report(p_after_wrap, "TMCCT should be reset to the initial-count");
+	report(p2o_not_reset, "TMCCT should not be reset to init");
+	report(p2o_reached_zero, "TMCCT should have reach zero");
+	report(p2o_stay_zero, "TMCCT should stay at zero");
 }
 
 #define KVM_HC_SEND_IPI 10
-- 
2.47.3