VIRTIO_F_ORDER_PLATFORM is required to use proper memory barriers
in case of HW vhost implementations like vDPA.
DMA barriers (rte_cio_*) are sufficent for that purpose.
Previously known as VIRTIO_F_IO_BARRIER.
Signed-off-by: Ilya Maximets <i.maxim...@samsung.com>
---
Based on "[RFC] net/virtio: use real barriers for vDPA".
RFC --> PATCH:
* Dropped vendor-specific hack to determine if we need real barriers.
* Added VIRTIO_F_ORDER_PLATFORM feature definition and checking.
Note: Patch to change the name of the feature from VIRTIO_F_IO_BARRIER
to VIRTIO_F_ORDER_PLATFORM is not merged yet:
https://www.mail-archive.com/virtio-dev@lists.oasis-open.org/msg04114.html
drivers/net/virtio/virtio_ethdev.c | 2 ++
drivers/net/virtio/virtio_ethdev.h | 3 ++-
drivers/net/virtio/virtio_pci.h | 7 ++++++
drivers/net/virtio/virtio_rxtx.c | 14 ++++++------
drivers/net/virtio/virtqueue.h | 35 +++++++++++++++++++++++++-----
5 files changed, 48 insertions(+), 13 deletions(-)
diff --git a/drivers/net/virtio/virtio_ethdev.c
b/drivers/net/virtio/virtio_ethdev.c
index cb2b2e0bf..5ae7a9650 100644
--- a/drivers/net/virtio/virtio_ethdev.c
+++ b/drivers/net/virtio/virtio_ethdev.c
@@ -1474,6 +1474,8 @@ virtio_init_device(struct rte_eth_dev *eth_dev, uint64_t
req_features)
if (virtio_negotiate_features(hw, req_features) < 0)
return -1;
+ hw->weak_barriers = !vtpci_with_feature(hw, VIRTIO_F_ORDER_PLATFORM);
+
if (!hw->virtio_user_dev) {
pci_dev = RTE_ETH_DEV_TO_PCI(eth_dev);
rte_eth_copy_pci_info(eth_dev, pci_dev);
diff --git a/drivers/net/virtio/virtio_ethdev.h
b/drivers/net/virtio/virtio_ethdev.h
index e0f80e5a4..c098e5ac0 100644
--- a/drivers/net/virtio/virtio_ethdev.h
+++ b/drivers/net/virtio/virtio_ethdev.h
@@ -34,7 +34,8 @@
1u << VIRTIO_RING_F_INDIRECT_DESC | \
1ULL << VIRTIO_F_VERSION_1 | \
1ULL << VIRTIO_F_IN_ORDER | \
- 1ULL << VIRTIO_F_IOMMU_PLATFORM)
+ 1ULL << VIRTIO_F_IOMMU_PLATFORM | \
+ 1ULL << VIRTIO_F_ORDER_PLATFORM)
#define VIRTIO_PMD_SUPPORTED_GUEST_FEATURES \
(VIRTIO_PMD_DEFAULT_GUEST_FEATURES | \
diff --git a/drivers/net/virtio/virtio_pci.h b/drivers/net/virtio/virtio_pci.h
index e961a58ca..e2f096185 100644
--- a/drivers/net/virtio/virtio_pci.h
+++ b/drivers/net/virtio/virtio_pci.h
@@ -128,6 +128,12 @@ struct virtnet_ctl;
*/
#define VIRTIO_F_IN_ORDER 35
+/*
+ * This feature indicates that memory accesses by the driver and the device
+ * are ordered in a way described by the platform.
+ */
+#define VIRTIO_F_ORDER_PLATFORM 36
+
/* The Guest publishes the used index for which it expects an interrupt
* at the end of the avail ring. Host should ignore the avail->flags field. */
/* The Host publishes the avail index for which it expects a kick
@@ -240,6 +246,7 @@ struct virtio_hw {
uint8_t use_simple_rx;
uint8_t use_inorder_rx;
uint8_t use_inorder_tx;
+ uint8_t weak_barriers;
bool has_tx_offload;
bool has_rx_offload;
uint16_t port_id;
diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
index cb8f89f18..66195bf47 100644
--- a/drivers/net/virtio/virtio_rxtx.c
+++ b/drivers/net/virtio/virtio_rxtx.c
@@ -906,7 +906,7 @@ virtio_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
uint16_t nb_pkts)
nb_used = VIRTQUEUE_NUSED(vq);
- virtio_rmb();
+ virtio_rmb(hw->weak_barriers);
num = likely(nb_used <= nb_pkts) ? nb_used : nb_pkts;
if (unlikely(num > VIRTIO_MBUF_BURST_SZ))
@@ -1017,7 +1017,7 @@ virtio_recv_mergeable_pkts_inorder(void *rx_queue,
nb_used = RTE_MIN(nb_used, nb_pkts);
nb_used = RTE_MIN(nb_used, VIRTIO_MBUF_BURST_SZ);
- virtio_rmb();
+ virtio_rmb(hw->weak_barriers);
PMD_RX_LOG(DEBUG, "used:%d", nb_used);
@@ -1202,7 +1202,7 @@ virtio_recv_mergeable_pkts(void *rx_queue,
nb_used = VIRTQUEUE_NUSED(vq);
- virtio_rmb();
+ virtio_rmb(hw->weak_barriers);
PMD_RX_LOG(DEBUG, "used:%d", nb_used);
@@ -1365,7 +1365,7 @@ virtio_xmit_pkts(void *tx_queue, struct rte_mbuf
**tx_pkts, uint16_t nb_pkts)
PMD_TX_LOG(DEBUG, "%d packets to xmit", nb_pkts);
nb_used = VIRTQUEUE_NUSED(vq);
- virtio_rmb();
+ virtio_rmb(hw->weak_barriers);
if (likely(nb_used > vq->vq_nentries - vq->vq_free_thresh))
virtio_xmit_cleanup(vq, nb_used);
@@ -1407,7 +1407,7 @@ virtio_xmit_pkts(void *tx_queue, struct rte_mbuf
**tx_pkts, uint16_t nb_pkts)
/* Positive value indicates it need free vring descriptors */
if (unlikely(need > 0)) {
nb_used = VIRTQUEUE_NUSED(vq);
- virtio_rmb();
+ virtio_rmb(hw->weak_barriers);
need = RTE_MIN(need, (int)nb_used);
virtio_xmit_cleanup(vq, need);
@@ -1463,7 +1463,7 @@ virtio_xmit_pkts_inorder(void *tx_queue,
PMD_TX_LOG(DEBUG, "%d packets to xmit", nb_pkts);
nb_used = VIRTQUEUE_NUSED(vq);
- virtio_rmb();
+ virtio_rmb(hw->weak_barriers);
if (likely(nb_used > vq->vq_nentries - vq->vq_free_thresh))
virtio_xmit_cleanup_inorder(vq, nb_used);
@@ -1511,7 +1511,7 @@ virtio_xmit_pkts_inorder(void *tx_queue,
need = slots - vq->vq_free_cnt;
if (unlikely(need > 0)) {
nb_used = VIRTQUEUE_NUSED(vq);
- virtio_rmb();
+ virtio_rmb(hw->weak_barriers);
need = RTE_MIN(need, (int)nb_used);
virtio_xmit_cleanup_inorder(vq, need);
diff --git a/drivers/net/virtio/virtqueue.h b/drivers/net/virtio/virtqueue.h
index 26518ed98..6b9055a1f 100644
--- a/drivers/net/virtio/virtqueue.h
+++ b/drivers/net/virtio/virtqueue.h
@@ -19,15 +19,40 @@
struct rte_mbuf;
/*
- * Per virtio_config.h in Linux.
+ * Per virtio_ring.h in Linux.
* For virtio_pci on SMP, we don't need to order with respect to MMIO
* accesses through relaxed memory I/O windows, so smp_mb() et al are
* sufficient.
*
+ * For using virtio to talk to real devices (eg. vDPA) we do need real
+ * barriers.
*/
-#define virtio_mb() rte_smp_mb()
-#define virtio_rmb() rte_smp_rmb()
-#define virtio_wmb() rte_smp_wmb()
+static inline void
+virtio_mb(uint8_t weak_barriers)
+{
+ if (weak_barriers)
+ rte_smp_mb();
+ else
+ rte_mb();
+}
+
+static inline void
+virtio_rmb(uint8_t weak_barriers)
+{
+ if (weak_barriers)
+ rte_smp_rmb();
+ else
+ rte_cio_rmb();
+}
+
+static inline void
+virtio_wmb(uint8_t weak_barriers)
+{
+ if (weak_barriers)
+ rte_smp_wmb();
+ else
+ rte_cio_wmb();
+}
#ifdef RTE_PMD_PACKET_PREFETCH
#define rte_packet_prefetch(p) rte_prefetch1(p)
@@ -312,7 +337,7 @@ void vq_ring_free_inorder(struct virtqueue *vq, uint16_t
desc_idx,
static inline void
vq_update_avail_idx(struct virtqueue *vq)
{
- virtio_wmb();
+ virtio_wmb(vq->hw->weak_barriers);
vq->vq_ring.avail->idx = vq->vq_avail_idx;
}
--
2.17.1
