From 9edf80a5eff51ebc6944876018952dc2505160bd Mon Sep 17 00:00:00 2001
From: Laurent Vivier <lvivier@redhat.com>
Date: Mon, 24 Apr 2017 16:45:25 +0200
Subject: [PATCH 15/23] virtio-rng: stop virtqueue while the CPU is stopped

RH-Author: Laurent Vivier <lvivier@redhat.com>
Message-id: <20170424164525.31342-1-lvivier@redhat.com>
Patchwork-id: 74859
O-Subject: [RHV-7.4 qemu-kvm-rhev PATCH] virtio-rng: stop virtqueue while the CPU is stopped
Bugzilla: 1435521
RH-Acked-by: Juan Quintela <quintela@redhat.com>
RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>

If we modify the virtio-rng virqueue while the
vmstate is already migrated we can have some
inconsistencies between the virtqueue state and
the memory content.

To avoid this, stop the virtqueue while the CPU
is stopped.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by:  Amit Shah <amit@kernel.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
(cherry picked from commit a23a6d183986ef38b705e85cabdd2af6cdc95276)
Signed-off-by: Laurent Vivier <lvivier@redhat.com>

BZ: https://bugzilla.redhat.com/show_bug.cgi?id=1435521
BREW: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=13071542
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 hw/virtio/trace-events         |  3 +++
 hw/virtio/virtio-rng.c         | 29 +++++++++++++++++++++++------
 include/hw/virtio/virtio-rng.h |  2 ++
 3 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
index 6926eed..1f7a7c1 100644
--- a/hw/virtio/trace-events
+++ b/hw/virtio/trace-events
@@ -11,8 +11,11 @@ virtio_set_status(void *vdev, uint8_t val) "vdev %p val %u"
 
 # hw/virtio/virtio-rng.c
 virtio_rng_guest_not_ready(void *rng) "rng %p: guest not ready"
+virtio_rng_cpu_is_stopped(void *rng, int size) "rng %p: cpu is stopped, dropping %d bytes"
+virtio_rng_popped(void *rng) "rng %p: elem popped"
 virtio_rng_pushed(void *rng, size_t len) "rng %p: %zd bytes pushed"
 virtio_rng_request(void *rng, size_t size, unsigned quota) "rng %p: %zd bytes requested, %u bytes quota left"
+virtio_rng_vm_state_change(void *rng, int running, int state) "rng %p: state change to running %d state %d"
 
 # hw/virtio/virtio-balloon.c
 #
diff --git a/hw/virtio/virtio-rng.c b/hw/virtio/virtio-rng.c
index 9639f4e..a6ee501 100644
--- a/hw/virtio/virtio-rng.c
+++ b/hw/virtio/virtio-rng.c
@@ -53,6 +53,15 @@ static void chr_read(void *opaque, const void *buf, size_t size)
         return;
     }
 
+    /* we can't modify the virtqueue until
+     * our state is fully synced
+     */
+
+    if (!runstate_check(RUN_STATE_RUNNING)) {
+        trace_virtio_rng_cpu_is_stopped(vrng, size);
+        return;
+    }
+
     vrng->quota_remaining -= size;
 
     offset = 0;
@@ -61,6 +70,7 @@ static void chr_read(void *opaque, const void *buf, size_t size)
         if (!elem) {
             break;
         }
+        trace_virtio_rng_popped(vrng);
         len = iov_from_buf(elem->in_sg, elem->in_num,
                            0, buf + offset, size - offset);
         offset += len;
@@ -120,17 +130,21 @@ static uint64_t get_features(VirtIODevice *vdev, uint64_t f, Error **errp)
     return f;
 }
 
-static int virtio_rng_post_load(void *opaque, int version_id)
+static void virtio_rng_vm_state_change(void *opaque, int running,
+                                       RunState state)
 {
     VirtIORNG *vrng = opaque;
 
+    trace_virtio_rng_vm_state_change(vrng, running, state);
+
     /* We may have an element ready but couldn't process it due to a quota
-     * limit.  Make sure to try again after live migration when the quota may
-     * have been reset.
+     * limit or because CPU was stopped.  Make sure to try again when the
+     * CPU restart.
      */
-    virtio_rng_process(vrng);
 
-    return 0;
+    if (running && is_guest_ready(vrng)) {
+        virtio_rng_process(vrng);
+    }
 }
 
 static void check_rate_limit(void *opaque)
@@ -198,6 +212,9 @@ static void virtio_rng_device_realize(DeviceState *dev, Error **errp)
     vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
                                                check_rate_limit, vrng);
     vrng->activate_timer = true;
+
+    vrng->vmstate = qemu_add_vm_change_state_handler(virtio_rng_vm_state_change,
+                                                     vrng);
 }
 
 static void virtio_rng_device_unrealize(DeviceState *dev, Error **errp)
@@ -205,6 +222,7 @@ static void virtio_rng_device_unrealize(DeviceState *dev, Error **errp)
     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
     VirtIORNG *vrng = VIRTIO_RNG(dev);
 
+    qemu_del_vm_change_state_handler(vrng->vmstate);
     timer_del(vrng->rate_limit_timer);
     timer_free(vrng->rate_limit_timer);
     virtio_cleanup(vdev);
@@ -218,7 +236,6 @@ static const VMStateDescription vmstate_virtio_rng = {
         VMSTATE_VIRTIO_DEVICE,
         VMSTATE_END_OF_LIST()
     },
-    .post_load =  virtio_rng_post_load,
 };
 
 static Property virtio_rng_properties[] = {
diff --git a/include/hw/virtio/virtio-rng.h b/include/hw/virtio/virtio-rng.h
index 2d40abd..922dce7 100644
--- a/include/hw/virtio/virtio-rng.h
+++ b/include/hw/virtio/virtio-rng.h
@@ -45,6 +45,8 @@ typedef struct VirtIORNG {
     QEMUTimer *rate_limit_timer;
     int64_t quota_remaining;
     bool activate_timer;
+
+    VMChangeStateEntry *vmstate;
 } VirtIORNG;
 
 #endif
-- 
1.8.3.1