[PATCH v2] virtio: Use auto rcu_read macros

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Use RCU_READ_LOCK_GUARD and WITH_RCU_READ_LOCK_GUARD
to replace the manual rcu_read_(un)lock calls.

I think the only change is virtio_load which was missing unlocks
in error paths; those end up being fatal errors so it's not
that important anyway.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 hw/virtio/virtio.c | 65 ++++++++++++++++------------------------------
 1 file changed, 23 insertions(+), 42 deletions(-)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 2e91dec567..7cb67702d0 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -387,7 +387,8 @@ static inline void vring_set_avail_event(VirtQueue *vq, uint16_t val)
 
 static void virtio_queue_split_set_notification(VirtQueue *vq, int enable)
 {
-    rcu_read_lock();
+    RCU_READ_LOCK_GUARD();
+
     if (virtio_vdev_has_feature(vq->vdev, VIRTIO_RING_F_EVENT_IDX)) {
         vring_set_avail_event(vq, vring_avail_idx(vq));
     } else if (enable) {
@@ -399,7 +400,6 @@ static void virtio_queue_split_set_notification(VirtQueue *vq, int enable)
         /* Expose avail event/used flags before caller checks the avail idx. */
         smp_mb();
     }
-    rcu_read_unlock();
 }
 
 static void virtio_queue_packed_set_notification(VirtQueue *vq, int enable)
@@ -408,7 +408,7 @@ static void virtio_queue_packed_set_notification(VirtQueue *vq, int enable)
     VRingPackedDescEvent e;
     VRingMemoryRegionCaches *caches;
 
-    rcu_read_lock();
+    RCU_READ_LOCK_GUARD();
     caches  = vring_get_region_caches(vq);
     vring_packed_event_read(vq->vdev, &caches->used, &e);
 
@@ -429,7 +429,6 @@ static void virtio_queue_packed_set_notification(VirtQueue *vq, int enable)
         /* Expose avail event/used flags before caller checks the avail idx. */
         smp_mb();
     }
-    rcu_read_unlock();
 }
 
 void virtio_queue_set_notification(VirtQueue *vq, int enable)
@@ -577,9 +576,8 @@ static int virtio_queue_split_empty(VirtQueue *vq)
         return 0;
     }
 
-    rcu_read_lock();
+    RCU_READ_LOCK_GUARD();
     empty = vring_avail_idx(vq) == vq->last_avail_idx;
-    rcu_read_unlock();
     return empty;
 }
 
@@ -601,12 +599,8 @@ static int virtio_queue_packed_empty_rcu(VirtQueue *vq)
 
 static int virtio_queue_packed_empty(VirtQueue *vq)
 {
-    bool empty;
-
-    rcu_read_lock();
-    empty = virtio_queue_packed_empty_rcu(vq);
-    rcu_read_unlock();
-    return empty;
+    RCU_READ_LOCK_GUARD();
+    return virtio_queue_packed_empty_rcu(vq);
 }
 
 int virtio_queue_empty(VirtQueue *vq)
@@ -859,10 +853,9 @@ void virtqueue_flush(VirtQueue *vq, unsigned int count)
 void virtqueue_push(VirtQueue *vq, const VirtQueueElement *elem,
                     unsigned int len)
 {
-    rcu_read_lock();
+    RCU_READ_LOCK_GUARD();
     virtqueue_fill(vq, elem, len, 0);
     virtqueue_flush(vq, 1);
-    rcu_read_unlock();
 }
 
 /* Called within rcu_read_lock().  */
@@ -943,7 +936,8 @@ static void virtqueue_split_get_avail_bytes(VirtQueue *vq,
     int64_t len = 0;
     int rc;
 
-    rcu_read_lock();
+    RCU_READ_LOCK_GUARD();
+
     idx = vq->last_avail_idx;
     total_bufs = in_total = out_total = 0;
 
@@ -1033,7 +1027,6 @@ done:
     if (out_bytes) {
         *out_bytes = out_total;
     }
-    rcu_read_unlock();
     return;
 
 err:
@@ -1083,7 +1076,7 @@ static void virtqueue_packed_get_avail_bytes(VirtQueue *vq,
     VRingPackedDesc desc;
     bool wrap_counter;
 
-    rcu_read_lock();
+    RCU_READ_LOCK_GUARD();
     idx = vq->last_avail_idx;
     wrap_counter = vq->last_avail_wrap_counter;
     total_bufs = in_total = out_total = 0;
@@ -1176,7 +1169,6 @@ done:
     if (out_bytes) {
         *out_bytes = out_total;
     }
-    rcu_read_unlock();
     return;
 
 err:
@@ -1360,7 +1352,7 @@ static void *virtqueue_split_pop(VirtQueue *vq, size_t sz)
     VRingDesc desc;
     int rc;
 
-    rcu_read_lock();
+    RCU_READ_LOCK_GUARD();
     if (virtio_queue_empty_rcu(vq)) {
         goto done;
     }
@@ -1469,7 +1461,6 @@ static void *virtqueue_split_pop(VirtQueue *vq, size_t sz)
     trace_virtqueue_pop(vq, elem, elem->in_num, elem->out_num);
 done:
     address_space_cache_destroy(&indirect_desc_cache);
-    rcu_read_unlock();
 
     return elem;
 
@@ -1494,7 +1485,7 @@ static void *virtqueue_packed_pop(VirtQueue *vq, size_t sz)
     uint16_t id;
     int rc;
 
-    rcu_read_lock();
+    RCU_READ_LOCK_GUARD();
     if (virtio_queue_packed_empty_rcu(vq)) {
         goto done;
     }
@@ -1600,7 +1591,6 @@ static void *virtqueue_packed_pop(VirtQueue *vq, size_t sz)
     trace_virtqueue_pop(vq, elem, elem->in_num, elem->out_num);
 done:
     address_space_cache_destroy(&indirect_desc_cache);
-    rcu_read_unlock();
 
     return elem;
 
@@ -2437,13 +2427,10 @@ static bool virtio_should_notify(VirtIODevice *vdev, VirtQueue *vq)
 
 void virtio_notify_irqfd(VirtIODevice *vdev, VirtQueue *vq)
 {
-    bool should_notify;
-    rcu_read_lock();
-    should_notify = virtio_should_notify(vdev, vq);
-    rcu_read_unlock();
-
-    if (!should_notify) {
-        return;
+    WITH_RCU_READ_LOCK_GUARD() {
+        if (!virtio_should_notify(vdev, vq)) {
+            return;
+        }
     }
 
     trace_virtio_notify_irqfd(vdev, vq);
@@ -2475,13 +2462,10 @@ static void virtio_irq(VirtQueue *vq)
 
 void virtio_notify(VirtIODevice *vdev, VirtQueue *vq)
 {
-    bool should_notify;
-    rcu_read_lock();
-    should_notify = virtio_should_notify(vdev, vq);
-    rcu_read_unlock();
-
-    if (!should_notify) {
-        return;
+    WITH_RCU_READ_LOCK_GUARD() {
+        if (!virtio_should_notify(vdev, vq)) {
+            return;
+        }
     }
 
     trace_virtio_notify(vdev, vq);
@@ -3032,7 +3016,7 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id)
         vdev->start_on_kick = true;
     }
 
-    rcu_read_lock();
+    RCU_READ_LOCK_GUARD();
     for (i = 0; i < num; i++) {
         if (vdev->vq[i].vring.desc) {
             uint16_t nheads;
@@ -3087,7 +3071,6 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id)
             }
         }
     }
-    rcu_read_unlock();
 
     return 0;
 }
@@ -3290,12 +3273,11 @@ static void virtio_queue_packed_restore_last_avail_idx(VirtIODevice *vdev,
 static void virtio_queue_split_restore_last_avail_idx(VirtIODevice *vdev,
                                                       int n)
 {
-    rcu_read_lock();
+    RCU_READ_LOCK_GUARD();
     if (vdev->vq[n].vring.desc) {
         vdev->vq[n].last_avail_idx = vring_used_idx(&vdev->vq[n]);
         vdev->vq[n].shadow_avail_idx = vdev->vq[n].last_avail_idx;
     }
-    rcu_read_unlock();
 }
 
 void virtio_queue_restore_last_avail_idx(VirtIODevice *vdev, int n)
@@ -3315,11 +3297,10 @@ static void virtio_queue_packed_update_used_idx(VirtIODevice *vdev, int n)
 
 static void virtio_split_packed_update_used_idx(VirtIODevice *vdev, int n)
 {
-    rcu_read_lock();
+    RCU_READ_LOCK_GUARD();
     if (vdev->vq[n].vring.desc) {
         vdev->vq[n].used_idx = vring_used_idx(&vdev->vq[n]);
     }
-    rcu_read_unlock();
 }
 
 void virtio_queue_update_used_idx(VirtIODevice *vdev, int n)
-- 
2.23.0