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[Qemu-devel] [RFC v2 7/8] virtio: event suppression for packed ring
From: |
wexu |
Subject: |
[Qemu-devel] [RFC v2 7/8] virtio: event suppression for packed ring |
Date: |
Tue, 5 Jun 2018 15:08:02 -0400 |
From: Wei Xu <address@hidden>
Signed-off-by: Wei Xu <address@hidden>
Signed-off-by: Wei Xu <address@hidden>
---
hw/virtio/virtio.c | 115 +++++++++++++++++++++++--
include/standard-headers/linux/virtio_config.h | 13 +++
2 files changed, 119 insertions(+), 9 deletions(-)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 6f2da83..4543974 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -226,6 +226,24 @@ static void vring_desc_read(VirtIODevice *vdev, VRingDesc
*desc,
virtio_tswap16s(vdev, &desc->next);
}
+static void vring_packed_event_read(VirtIODevice *vdev,
+ MemoryRegionCache *cache, VRingPackedDescEvent *e)
+{
+ address_space_read_cached(cache, 0, e, sizeof(*e));
+ virtio_tswap16s(vdev, &e->off_wrap);
+ virtio_tswap16s(vdev, &e->flags);
+}
+
+static void vring_packed_event_write(VirtIODevice *vdev,
+ MemoryRegionCache *cache, VRingPackedDescEvent *e)
+{
+ virtio_tswap16s(vdev, &e->off_wrap);
+ virtio_tswap16s(vdev, &e->flags);
+ address_space_write_cached(cache, 0, e, sizeof(*e));
+ address_space_cache_invalidate(cache, 0, sizeof(VRingUsedElem));
+}
+
+
static VRingMemoryRegionCaches *vring_get_region_caches(struct VirtQueue *vq)
{
VRingMemoryRegionCaches *caches = atomic_rcu_read(&vq->vring.caches);
@@ -332,14 +350,8 @@ static inline void vring_set_avail_event(VirtQueue *vq,
uint16_t val)
address_space_cache_invalidate(&caches->used, pa, sizeof(val));
}
-void virtio_queue_set_notification(VirtQueue *vq, int enable)
+static void virtio_queue_set_notification_split(VirtQueue *vq, int enable)
{
- vq->notification = enable;
-
- if (!vq->vring.desc) {
- return;
- }
-
rcu_read_lock();
if (virtio_vdev_has_feature(vq->vdev, VIRTIO_RING_F_EVENT_IDX)) {
vring_set_avail_event(vq, vring_avail_idx(vq));
@@ -355,6 +367,38 @@ void virtio_queue_set_notification(VirtQueue *vq, int
enable)
rcu_read_unlock();
}
+static void virtio_queue_set_notification_packed(VirtQueue *vq, int enable)
+{
+ VRingPackedDescEvent e;
+ VRingMemoryRegionCaches *caches;
+
+ rcu_read_lock();
+ caches = vring_get_region_caches(vq);
+ vring_packed_event_read(vq->vdev, &caches->device, &e);
+ if (enable) {
+ e.flags = RING_EVENT_FLAGS_ENABLE;
+ } else {
+ e.flags = RING_EVENT_FLAGS_DISABLE;
+ }
+ vring_packed_event_write(vq->vdev, &caches->device, &e);
+ rcu_read_unlock();
+}
+
+void virtio_queue_set_notification(VirtQueue *vq, int enable)
+{
+ vq->notification = enable;
+
+ if (!vq->vring.desc) {
+ return;
+ }
+
+ if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) {
+ virtio_queue_set_notification_packed(vq, enable);
+ } else {
+ virtio_queue_set_notification_split(vq, enable);
+ }
+}
+
int virtio_queue_ready(VirtQueue *vq)
{
return vq->vring.avail != 0;
@@ -2059,8 +2103,7 @@ static void virtio_set_isr(VirtIODevice *vdev, int value)
}
}
-/* Called within rcu_read_lock(). */
-static bool virtio_should_notify(VirtIODevice *vdev, VirtQueue *vq)
+static bool virtio_split_should_notify(VirtIODevice *vdev, VirtQueue *vq)
{
uint16_t old, new;
bool v;
@@ -2083,6 +2126,60 @@ static bool virtio_should_notify(VirtIODevice *vdev,
VirtQueue *vq)
return !v || vring_need_event(vring_get_used_event(vq), new, old);
}
+static bool vring_packed_need_event(VirtQueue *vq, uint16_t off_wrap,
+ uint16_t new, uint16_t old)
+{
+ bool wrap = vq->used_wrap_counter;
+ int off = off_wrap & ~(1 << 15);
+
+ if (new < old) {
+ new += vq->vring.num;
+ wrap ^= 1;
+ }
+
+ if (wrap != off_wrap >> 15) {
+ off += vq->vring.num;
+ }
+
+ return vring_need_event(off, new, old);
+}
+
+static bool virtio_packed_should_notify(VirtIODevice *vdev, VirtQueue *vq)
+{
+ VRingPackedDescEvent e;
+ uint16_t old, new;
+ bool v;
+ VRingMemoryRegionCaches *caches;
+
+ caches = vring_get_region_caches(vq);
+ vring_packed_event_read(vdev, &caches->driver, &e);
+
+ /* Make sure we see the updated flags */
+ smp_mb();
+ if (e.flags == RING_EVENT_FLAGS_DISABLE) {
+ return false;
+ } else if (e.flags == RING_EVENT_FLAGS_ENABLE) {
+ return true;
+ }
+
+ v = vq->signalled_used_valid;
+ vq->signalled_used_valid = true;
+ old = vq->signalled_used;
+ new = vq->signalled_used = vq->used_idx;
+
+ return !v || vring_packed_need_event(vq, e.off_wrap, new, old);
+}
+
+/* Called within rcu_read_lock(). */
+static bool virtio_should_notify(VirtIODevice *vdev, VirtQueue *vq)
+{
+ if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
+ return virtio_packed_should_notify(vdev, vq);
+ } else {
+ return virtio_split_should_notify(vdev, vq);
+ }
+}
+
void virtio_notify_irqfd(VirtIODevice *vdev, VirtQueue *vq)
{
bool should_notify;
diff --git a/include/standard-headers/linux/virtio_config.h
b/include/standard-headers/linux/virtio_config.h
index 6ee5529..53e5c83 100644
--- a/include/standard-headers/linux/virtio_config.h
+++ b/include/standard-headers/linux/virtio_config.h
@@ -73,4 +73,17 @@
#define VIRTIO_F_IOMMU_PLATFORM 33
#define VIRTIO_F_RING_PACKED 34
+
+/* Enable events */
+#define RING_EVENT_FLAGS_ENABLE 0x0
+/* Disable events */
+#define RING_EVENT_FLAGS_DISABLE 0x1
+/*
+ * * Enable events for a specific descriptor
+ * * (as specified by Descriptor Ring Change Event Offset/Wrap Counter).
+ * * Only valid if VIRTIO_F_RING_EVENT_IDX has been negotiated.
+ * */
+#define RING_EVENT_FLAGS_DESC 0x2
+/* The value 0x3 is reserved */
+
#endif /* _LINUX_VIRTIO_CONFIG_H */
--
1.8.3.1
- [Qemu-devel] [RFC v2 5/8] virtio: queue pop for packed ring, (continued)
[Qemu-devel] [RFC v2 6/8] virtio: flush/push for packed ring, wexu, 2018/06/05
[Qemu-devel] [RFC v2 8/8] virtio: guest driver reload for vhost-net, wexu, 2018/06/05
[Qemu-devel] [RFC v2 7/8] virtio: event suppression for packed ring,
wexu <=
Re: [Qemu-devel] [RFC v2 0/8] packed ring virtio-net userspace backend support, Jason Wang, 2018/06/05
Re: [Qemu-devel] [RFC v2 0/8] packed ring virtio-net userspace backend support, Jason Wang, 2018/06/05