[dpdk-dev,v5] vhost: support virtqueue interrupt/notification suppression
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Commit Message
The driver can suppress interrupt when VIRTIO_F_EVENT_IDX feature bit is
negotiated. The driver set vring flags to 0, and MAY use used_event in
available ring to advise device interrupt util reach an index specified
by used_event. The device ignore the lower bit of vring flags, and send
an interrupt when index reach used_event.
The device can suppress notification in a manner analogous to the ways
driver suppress interrupt. The device manipulates flags or avail_event in
the used ringin the same way the driver manipulates flags or used_event in
available ring.
This patch is to enable this feature in vhost.
Signed-off-by: Junjie Chen <junjie.j.chen@intel.com>
v5:
Remove updating avail event index in backend.
v2-v4:
Use definition of VIRTIO_F_EVENT_IDX from kernel.
---
lib/librte_vhost/Makefile | 1 +
lib/librte_vhost/vhost.h | 3 +++
lib/librte_vhost/virtio_net.c | 47 +++++++++++++++++++++++++++++--------------
3 files changed, 36 insertions(+), 15 deletions(-)
Comments
Hi,
> -----Original Message-----
> From: Chen, Junjie J
> Sent: Sunday, December 24, 2017 12:56 AM
> To: yliu@fridaylinux.org; maxime.coquelin@redhat.com; Bie, Tiwei
> <tiwei.bie@intel.com>; Wang, Xiao W <xiao.w.wang@intel.com>
> Cc: dev@dpdk.org; Chen, Junjie J <junjie.j.chen@intel.com>
> Subject: [PATCH v5] vhost: support virtqueue interrupt/notification
> suppression
>
> The driver can suppress interrupt when VIRTIO_F_EVENT_IDX feature bit is
> negotiated. The driver set vring flags to 0, and MAY use used_event in
> available ring to advise device interrupt util reach an index specified
> by used_event. The device ignore the lower bit of vring flags, and send
> an interrupt when index reach used_event.
>
> The device can suppress notification in a manner analogous to the ways
> driver suppress interrupt. The device manipulates flags or avail_event in
> the used ringin the same way the driver manipulates flags or used_event in
> available ring.
>
> This patch is to enable this feature in vhost.
>
> Signed-off-by: Junjie Chen <junjie.j.chen@intel.com>
>
[...]
> + /* Last used index we notify to front end. */
> + uint16_t signalled_used;
> #define VIRTIO_INVALID_EVENTFD (-1)
> #define VIRTIO_UNINITIALIZED_EVENTFD (-2)
>
> @@ -211,6 +213,7 @@ struct vhost_msg {
> (1ULL << VIRTIO_NET_F_GUEST_TSO4) | \
> (1ULL << VIRTIO_NET_F_GUEST_TSO6) | \
> (1ULL << VIRTIO_RING_F_INDIRECT_DESC) | \
> + (1ULL << VIRTIO_RING_F_EVENT_IDX) | \
> (1ULL << VIRTIO_NET_F_MTU) | \
> (1ULL << VIRTIO_F_IOMMU_PLATFORM))
>
> diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
> index 6fee16e..2badeda 100644
> --- a/lib/librte_vhost/virtio_net.c
> +++ b/lib/librte_vhost/virtio_net.c
> @@ -52,6 +52,35 @@
>
> #define MAX_BATCH_LEN 256
>
> +#define vhost_used_event(vr) ((vr)->avail->ring[(vr)->size])
> +#define vhost_avail_event(vr) \
> + (*(volatile uint16_t *)&(vr)->used->ring[(vr)->size])
> +
From vhost side, vhost_used_event(vr) is volatile.
BRs,
Xiao
@@ -40,6 +40,7 @@ LIBABIVER := 4
CFLAGS += $(WERROR_FLAGS) -I$(SRCDIR) -O3 -D_FILE_OFFSET_BITS=64
CFLAGS += -I vhost_user
+CFLAGS += -fno-strict-aliasing
LDLIBS += -lpthread
ifeq ($(CONFIG_RTE_LIBRTE_VHOST_NUMA),y)
@@ -103,6 +103,8 @@ struct vhost_virtqueue {
uint16_t last_avail_idx;
uint16_t last_used_idx;
+ /* Last used index we notify to front end. */
+ uint16_t signalled_used;
#define VIRTIO_INVALID_EVENTFD (-1)
#define VIRTIO_UNINITIALIZED_EVENTFD (-2)
@@ -211,6 +213,7 @@ struct vhost_msg {
(1ULL << VIRTIO_NET_F_GUEST_TSO4) | \
(1ULL << VIRTIO_NET_F_GUEST_TSO6) | \
(1ULL << VIRTIO_RING_F_INDIRECT_DESC) | \
+ (1ULL << VIRTIO_RING_F_EVENT_IDX) | \
(1ULL << VIRTIO_NET_F_MTU) | \
(1ULL << VIRTIO_F_IOMMU_PLATFORM))
@@ -52,6 +52,35 @@
#define MAX_BATCH_LEN 256
+#define vhost_used_event(vr) ((vr)->avail->ring[(vr)->size])
+#define vhost_avail_event(vr) \
+ (*(volatile uint16_t *)&(vr)->used->ring[(vr)->size])
+
+static __rte_always_inline void
+vhost_notify(struct virtio_net *dev, struct vhost_virtqueue *vq)
+{
+ /* Don't notify guest if we don't reach index specified by guest. */
+ if (dev->features & (1ULL << VIRTIO_RING_F_EVENT_IDX)) {
+ uint16_t old = vq->signalled_used;
+ uint16_t new = vq->last_used_idx;
+
+ LOG_DEBUG(VHOST_DATA, "%s: used_event_idx=%d, old=%d, new=%d\n",
+ __func__,
+ vhost_used_event(vq),
+ old, new);
+ if (vring_need_event(vhost_used_event(vq), new, old)
+ && (vq->callfd >= 0)) {
+ vq->signalled_used = vq->last_used_idx;
+ eventfd_write(vq->callfd, (eventfd_t) 1);
+ }
+ } else {
+ /* Kick the guest if necessary. */
+ if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
+ && (vq->callfd >= 0))
+ eventfd_write(vq->callfd, (eventfd_t)1);
+ }
+}
+
static bool
is_valid_virt_queue_idx(uint32_t idx, int is_tx, uint32_t nr_vring)
{
@@ -410,11 +439,7 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
/* flush used->idx update before we read avail->flags. */
rte_mb();
-
- /* Kick the guest if necessary. */
- if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
- && (vq->callfd >= 0))
- eventfd_write(vq->callfd, (eventfd_t)1);
+ vhost_notify(dev, vq);
out:
if (dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM))
vhost_user_iotlb_rd_unlock(vq);
@@ -704,11 +729,7 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
/* flush used->idx update before we read avail->flags. */
rte_mb();
-
- /* Kick the guest if necessary. */
- if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
- && (vq->callfd >= 0))
- eventfd_write(vq->callfd, (eventfd_t)1);
+ vhost_notify(dev, vq);
}
out:
@@ -1106,11 +1127,7 @@ update_used_idx(struct virtio_net *dev, struct vhost_virtqueue *vq,
vq->used->idx += count;
vhost_log_used_vring(dev, vq, offsetof(struct vring_used, idx),
sizeof(vq->used->idx));
-
- /* Kick guest if required. */
- if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
- && (vq->callfd >= 0))
- eventfd_write(vq->callfd, (eventfd_t)1);
+ vhost_notify(dev, vq);
}
static __rte_always_inline struct zcopy_mbuf *