[Qemu-devel] [PATCH 1/2 v2] virtio-rng: Bump up quota value only when guest requests entropy

[Pankaj Gupta <pagupta@redhat.com>]

This patch triggers timer only when guest requests for 
entropy. As soon as first request from guest for entropy 
comes we set the timer. Timer bumps up the quota value 
when it gets triggered.

Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
---
 hw/virtio/virtio-rng.c         | 15 ++++++++-------
 include/hw/virtio/virtio-rng.h |  1 +
 2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/hw/virtio/virtio-rng.c b/hw/virtio/virtio-rng.c
index 22b1d87..8774a0c 100644
--- a/hw/virtio/virtio-rng.c
+++ b/hw/virtio/virtio-rng.c
@@ -78,6 +78,12 @@ static void virtio_rng_process(VirtIORNG *vrng)
         return;
     }
 
+    if (vrng->activate_timer) {
+        timer_mod(vrng->rate_limit_timer,
+                   qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
+        vrng->activate_timer = false;
+    }
+
     if (vrng->quota_remaining < 0) {
         quota = 0;
     } else {
@@ -139,8 +145,7 @@ static void check_rate_limit(void *opaque)
 
     vrng->quota_remaining = vrng->conf.max_bytes;
     virtio_rng_process(vrng);
-    timer_mod(vrng->rate_limit_timer,
-                   qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
+    vrng->activate_timer = true;
 }
 
 static void virtio_rng_device_realize(DeviceState *dev, Error **errp)
@@ -196,13 +201,9 @@ static void virtio_rng_device_realize(DeviceState *dev, Error **errp)
 
     vrng->vq = virtio_add_queue(vdev, 8, handle_input);
     vrng->quota_remaining = vrng->conf.max_bytes;
-
     vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
                                                check_rate_limit, vrng);
-
-    timer_mod(vrng->rate_limit_timer,
-                   qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
-
+    vrng->activate_timer = true;
     register_savevm(dev, "virtio-rng", -1, 1, virtio_rng_save,
                     virtio_rng_load, vrng);
 }
diff --git a/include/hw/virtio/virtio-rng.h b/include/hw/virtio/virtio-rng.h
index 0316488..3f07de7 100644
--- a/include/hw/virtio/virtio-rng.h
+++ b/include/hw/virtio/virtio-rng.h
@@ -44,6 +44,7 @@ typedef struct VirtIORNG {
      */
     QEMUTimer *rate_limit_timer;
     int64_t quota_remaining;
+    bool activate_timer;
 } VirtIORNG;
 
 #endif
-- 
1.9.3