If devices always use descriptors in the same order in which they have been made available. These devices can offer the VIRTIO_F_IN_ORDER feature. If negotiated, this knowledge allows devices to notify the use of a batch of buffers to virtio driver by only writing used ring index.
Vhost user device has supported this feature by default. If vhost dequeue zero is enabled, should disable VIRTIO_F_IN_ORDER as vhost can’t assure that descriptors returned from NIC are in order. Signed-off-by: Marvin Liu <yong....@intel.com> Reviewed-by: Maxime Coquelin <maxime.coque...@redhat.com> diff --git a/lib/librte_vhost/socket.c b/lib/librte_vhost/socket.c index 0399c37bc..d63031747 100644 --- a/lib/librte_vhost/socket.c +++ b/lib/librte_vhost/socket.c @@ -853,6 +853,12 @@ rte_vhost_driver_register(const char *path, uint64_t flags) vsocket->supported_features = VIRTIO_NET_SUPPORTED_FEATURES; vsocket->features = VIRTIO_NET_SUPPORTED_FEATURES; + /* Dequeue zero copy can't assure descriptors returned in order */ + if (vsocket->dequeue_zero_copy) { + vsocket->supported_features &= ~(1ULL << VIRTIO_F_IN_ORDER); + vsocket->features &= ~(1ULL << VIRTIO_F_IN_ORDER); + } + if (!(flags & RTE_VHOST_USER_IOMMU_SUPPORT)) { vsocket->supported_features &= ~(1ULL << VIRTIO_F_IOMMU_PLATFORM); vsocket->features &= ~(1ULL << VIRTIO_F_IOMMU_PLATFORM); diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h index 786a74f64..3437b996b 100644 --- a/lib/librte_vhost/vhost.h +++ b/lib/librte_vhost/vhost.h @@ -191,6 +191,13 @@ struct vhost_msg { #define VIRTIO_F_VERSION_1 32 #endif +/* + * Available and used descs are in same order + */ +#ifndef VIRTIO_F_IN_ORDER +#define VIRTIO_F_IN_ORDER 35 +#endif + /* Features supported by this builtin vhost-user net driver. */ #define VIRTIO_NET_SUPPORTED_FEATURES ((1ULL << VIRTIO_NET_F_MRG_RXBUF) | \ (1ULL << VIRTIO_F_ANY_LAYOUT) | \ @@ -214,7 +221,8 @@ struct vhost_msg { (1ULL << VIRTIO_NET_F_GUEST_ECN) | \ (1ULL << VIRTIO_RING_F_INDIRECT_DESC) | \ (1ULL << VIRTIO_RING_F_EVENT_IDX) | \ - (1ULL << VIRTIO_NET_F_MTU) | \ + (1ULL << VIRTIO_NET_F_MTU) | \ + (1ULL << VIRTIO_F_IN_ORDER) | \ (1ULL << VIRTIO_F_IOMMU_PLATFORM)) -- 2.17.0