libqos: use microseconds instead of iterations for virtio timeout

Some hosts are slow or overloaded so test execution takes a long time.
Test cases use timeouts to protect against an infinite loop stalling the
test forever (especially important in automated test setups).

Commit 6cd14054b67774cc58a51fca6660cfa1d3c08059 ("libqos virtio:
Increase ISR timeout") increased the clock_step() value in an attempt to
lengthen the virtio interrupt wait timeout, but timeout failures are
still occuring on the Travis automated testing platform.

This is because clock_step() only affects the guest's virtual time.
Virtio requests can be bottlenecked on host disk I/O latency - which
cannot be improved by stepping the clock, so the fix was ineffective.

This patch changes the qvirtio_wait_queue_isr() and
qvirtio_wait_config_isr() timeout mechanism from loop iterations to
microseconds.  This way the test case can specify an absolute 30 second
timeout.  Number of loop iterations is not a reliable timeout mechanism
since the speed depends on many factors including host performance.

Tests should no longer timeout on overloaded Travis instances.

Cc: Marc Marí <marc.mari.barcelo@gmail.com>
Reported-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

2 files changed, 20 insertions, 18 deletions

diff --git a/tests/libqos/virtio.c b/tests/libqos/virtio.c
index 009325dd02..a061289249 100644
--- a/tests/libqos/virtio.c
+++ b/tests/libqos/virtio.c
@@ -78,17 +78,18 @@ void qvirtio_set_driver_ok(const QVirtioBus *bus, QVirtioDevice *d)
                 QVIRTIO_DRIVER_OK | QVIRTIO_DRIVER | QVIRTIO_ACKNOWLEDGE);
 }
 
-bool qvirtio_wait_queue_isr(const QVirtioBus *bus, QVirtioDevice *d,
-                                            QVirtQueue *vq, uint64_t timeout)
+void qvirtio_wait_queue_isr(const QVirtioBus *bus, QVirtioDevice *d,
+                            QVirtQueue *vq, gint64 timeout_us)
 {
-    do {
+    gint64 start_time = g_get_monotonic_time();
+
+    for (;;) {
         clock_step(100);
         if (bus->get_queue_isr_status(d, vq)) {
-            break; /* It has ended */
+            return;
         }
-    } while (--timeout);
-
-    return timeout != 0;
+        g_assert(g_get_monotonic_time() - start_time <= timeout_us);
+    }
 }
 
 /* Wait for the status byte at given guest memory address to be set
@@ -113,17 +114,18 @@ uint8_t qvirtio_wait_status_byte_no_isr(const QVirtioBus *bus,
     return val;
 }
 
-bool qvirtio_wait_config_isr(const QVirtioBus *bus, QVirtioDevice *d,
-                                                            uint64_t timeout)
+void qvirtio_wait_config_isr(const QVirtioBus *bus, QVirtioDevice *d,
+                             gint64 timeout_us)
 {
-    do {
+    gint64 start_time = g_get_monotonic_time();
+
+    for (;;) {
         clock_step(100);
         if (bus->get_config_isr_status(d)) {
-            break; /* It has ended */
+            return;
         }
-    } while (--timeout);
-
-    return timeout != 0;
+        g_assert(g_get_monotonic_time() - start_time <= timeout_us);
+    }
 }
 
 void qvring_init(const QGuestAllocator *alloc, QVirtQueue *vq, uint64_t addr)
diff --git a/tests/libqos/virtio.h b/tests/libqos/virtio.h
index bc7518e880..29fbacbc99 100644
--- a/tests/libqos/virtio.h
+++ b/tests/libqos/virtio.h
@@ -160,15 +160,15 @@ void qvirtio_set_acknowledge(const QVirtioBus *bus, QVirtioDevice *d);
 void qvirtio_set_driver(const QVirtioBus *bus, QVirtioDevice *d);
 void qvirtio_set_driver_ok(const QVirtioBus *bus, QVirtioDevice *d);
 
-bool qvirtio_wait_queue_isr(const QVirtioBus *bus, QVirtioDevice *d,
-                                            QVirtQueue *vq, uint64_t timeout);
+void qvirtio_wait_queue_isr(const QVirtioBus *bus, QVirtioDevice *d,
+                            QVirtQueue *vq, gint64 timeout_us);
 uint8_t qvirtio_wait_status_byte_no_isr(const QVirtioBus *bus,
                                         QVirtioDevice *d,
                                         QVirtQueue *vq,
                                         uint64_t addr,
                                         gint64 timeout_us);
-bool qvirtio_wait_config_isr(const QVirtioBus *bus, QVirtioDevice *d,
-                                                            uint64_t timeout);
+void qvirtio_wait_config_isr(const QVirtioBus *bus, QVirtioDevice *d,
+                             gint64 timeout_us);
 QVirtQueue *qvirtqueue_setup(const QVirtioBus *bus, QVirtioDevice *d,
                                         QGuestAllocator *alloc, uint16_t index);