[dpdk-dev] [PATCH v7 1/8] net/virtio: vring init for packed queues
Maxime Coquelin
maxime.coquelin at redhat.com
Thu Oct 4 13:54:00 CEST 2018
On 10/03/2018 03:11 PM, Jens Freimann wrote:
> Add and initialize descriptor data structures.
>
> To allow out of order processing a .next field was added to
> struct vq_desc_extra because there is none in the packed virtqueue
> descriptor itself. This is used to chain descriptors and process them
> similiar to how it is handled for split virtqueues.
>
> Signed-off-by: Jens Freimann <jfreimann at redhat.com>
> ---
> drivers/net/virtio/virtio_ethdev.c | 28 +++++++++------
> drivers/net/virtio/virtio_pci.h | 8 +++++
> drivers/net/virtio/virtio_ring.h | 55 +++++++++++++++++++++++++++---
> drivers/net/virtio/virtqueue.h | 13 ++++++-
> 4 files changed, 88 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
> index b81df0a99..d6a1613dd 100644
> --- a/drivers/net/virtio/virtio_ethdev.c
> +++ b/drivers/net/virtio/virtio_ethdev.c
> @@ -299,19 +299,27 @@ virtio_init_vring(struct virtqueue *vq)
>
> PMD_INIT_FUNC_TRACE();
>
> - /*
> - * Reinitialise since virtio port might have been stopped and restarted
> - */
> memset(ring_mem, 0, vq->vq_ring_size);
> - vring_init(vr, size, ring_mem, VIRTIO_PCI_VRING_ALIGN);
> + vring_init(vq->hw, vr, size, ring_mem, VIRTIO_PCI_VRING_ALIGN);
> +
> + vq->vq_free_cnt = vq->vq_nentries;
> + memset(vq->vq_descx, 0, sizeof(struct vq_desc_extra) * vq->vq_nentries);
> vq->vq_used_cons_idx = 0;
> + vq->vq_avail_idx = 0;
> vq->vq_desc_head_idx = 0;
> - vq->vq_avail_idx = 0;
> vq->vq_desc_tail_idx = (uint16_t)(vq->vq_nentries - 1);
> - vq->vq_free_cnt = vq->vq_nentries;
> - memset(vq->vq_descx, 0, sizeof(struct vq_desc_extra) * vq->vq_nentries);
> + if (vtpci_packed_queue(vq->hw)) {
> + uint16_t i;
> + for(i = 0; i < size - 1; i++) {
> + vq->vq_descx[i].next = i + 1;
I would move it in a dedicated loop, and do it only if IN_ORDER hasn't
been negotiated. Not for performance reason of course, but just to
highlight that this extra stuff isn't needed with in-order.
> + vq->vq_ring.desc_packed[i].index = i;
I would use the vring_desc_init_packed function declared below instead.
> + }
Trailing space.
> + vq->vq_ring.desc_packed[i].index = i;
> + vq->vq_descx[i].next = VQ_RING_DESC_CHAIN_END;
> + } else {
>
> - vring_desc_init(vr->desc, size);
> + vring_desc_init_split(vr->desc, size);
> + }
>
> /*
> * Disable device(host) interrupting guest
> @@ -386,7 +394,7 @@ virtio_init_queue(struct rte_eth_dev *dev, uint16_t vtpci_queue_idx)
> /*
> * Reserve a memzone for vring elements
> */
> - size = vring_size(vq_size, VIRTIO_PCI_VRING_ALIGN);
> + size = vring_size(hw, vq_size, VIRTIO_PCI_VRING_ALIGN);
> vq->vq_ring_size = RTE_ALIGN_CEIL(size, VIRTIO_PCI_VRING_ALIGN);
> PMD_INIT_LOG(DEBUG, "vring_size: %d, rounded_vring_size: %d",
> size, vq->vq_ring_size);
> @@ -489,7 +497,7 @@ virtio_init_queue(struct rte_eth_dev *dev, uint16_t vtpci_queue_idx)
> for (i = 0; i < vq_size; i++) {
> struct vring_desc *start_dp = txr[i].tx_indir;
>
> - vring_desc_init(start_dp, RTE_DIM(txr[i].tx_indir));
> + vring_desc_init_split(start_dp, RTE_DIM(txr[i].tx_indir));
>
> /* first indirect descriptor is always the tx header */
> start_dp->addr = txvq->virtio_net_hdr_mem
> diff --git a/drivers/net/virtio/virtio_pci.h b/drivers/net/virtio/virtio_pci.h
> index 58fdd3d45..90204d281 100644
> --- a/drivers/net/virtio/virtio_pci.h
> +++ b/drivers/net/virtio/virtio_pci.h
> @@ -113,6 +113,8 @@ struct virtnet_ctl;
>
> #define VIRTIO_F_VERSION_1 32
> #define VIRTIO_F_IOMMU_PLATFORM 33
> +#define VIRTIO_F_RING_PACKED 34
> +#define VIRTIO_F_IN_ORDER 35
Isn't that feature already declared?
>
> /*
> * Some VirtIO feature bits (currently bits 28 through 31) are
> @@ -314,6 +316,12 @@ vtpci_with_feature(struct virtio_hw *hw, uint64_t bit)
> return (hw->guest_features & (1ULL << bit)) != 0;
> }
>
> +static inline int
> +vtpci_packed_queue(struct virtio_hw *hw)
> +{
> + return vtpci_with_feature(hw, VIRTIO_F_RING_PACKED);
> +}
> +
> /*
> * Function declaration from virtio_pci.c
> */
> diff --git a/drivers/net/virtio/virtio_ring.h b/drivers/net/virtio/virtio_ring.h
> index 9e3c2a015..309069fdb 100644
> --- a/drivers/net/virtio/virtio_ring.h
> +++ b/drivers/net/virtio/virtio_ring.h
> @@ -54,11 +54,38 @@ struct vring_used {
> struct vring_used_elem ring[0];
> };
>
> +/* For support of packed virtqueues in Virtio 1.1 the format of descriptors
> + * looks like this.
> + */
> +struct vring_desc_packed {
> + uint64_t addr;
> + uint32_t len;
> + uint16_t index;
> + uint16_t flags;
> +} __attribute__ ((aligned(16)));
> +
> +#define RING_EVENT_FLAGS_ENABLE 0x0
> +#define RING_EVENT_FLAGS_DISABLE 0x1
> +#define RING_EVENT_FLAGS_DESC 0x2
> +struct vring_packed_desc_event {
> + uint16_t desc_event_off_wrap;
> + uint16_t desc_event_flags;
> +};
> +
> struct vring {
> unsigned int num;
> - struct vring_desc *desc;
> - struct vring_avail *avail;
> - struct vring_used *used;
> + union {
> + struct vring_desc_packed *desc_packed;
> + struct vring_desc *desc;
> + };
> + union {
> + struct vring_avail *avail;
> + struct vring_packed_desc_event *driver_event;
> + };
> + union {
> + struct vring_used *used;
> + struct vring_packed_desc_event *device_event;
> + };
> };
>
> /* The standard layout for the ring is a continuous chunk of memory which
> @@ -95,10 +122,18 @@ struct vring {
> #define vring_avail_event(vr) (*(uint16_t *)&(vr)->used->ring[(vr)->num])
>
> static inline size_t
> -vring_size(unsigned int num, unsigned long align)
> +vring_size(struct virtio_hw *hw, unsigned int num, unsigned long align)
> {
> size_t size;
>
> + if (vtpci_packed_queue(hw)) {
> + size = num * sizeof(struct vring_desc_packed);
> + size += sizeof(struct vring_packed_desc_event);
> + size = RTE_ALIGN_CEIL(size, align);
> + size += sizeof(struct vring_packed_desc_event);
> + return size;
> + }
> +
> size = num * sizeof(struct vring_desc);
> size += sizeof(struct vring_avail) + (num * sizeof(uint16_t));
> size = RTE_ALIGN_CEIL(size, align);
> @@ -108,10 +143,20 @@ vring_size(unsigned int num, unsigned long align)
> }
>
> static inline void
> -vring_init(struct vring *vr, unsigned int num, uint8_t *p,
> +vring_init(struct virtio_hw *hw, struct vring *vr, unsigned int num, uint8_t *p,
> unsigned long align)
> {
> vr->num = num;
> + if (vtpci_packed_queue(hw)) {
> + vr->desc_packed = (struct vring_desc_packed *)p;
> + vr->driver_event = (struct vring_packed_desc_event *)(p +
> + num * sizeof(struct vring_desc_packed));
> + vr->device_event = (struct vring_packed_desc_event *)
> + RTE_ALIGN_CEIL((uintptr_t)(vr->driver_event +
> + sizeof(struct vring_packed_desc_event)), align);
> + return;
> + }
> +
As a general comment, I would find it cleaner to have dedicated
functions for split and packed variants, like vring_init_split,
vring_init_packed, etc...
> vr->desc = (struct vring_desc *) p;
> vr->avail = (struct vring_avail *) (p +
> num * sizeof(struct vring_desc));
> diff --git a/drivers/net/virtio/virtqueue.h b/drivers/net/virtio/virtqueue.h
> index 26518ed98..6a4f92b79 100644
> --- a/drivers/net/virtio/virtqueue.h
> +++ b/drivers/net/virtio/virtqueue.h
> @@ -161,6 +161,7 @@ struct virtio_pmd_ctrl {
> struct vq_desc_extra {
> void *cookie;
> uint16_t ndescs;
> + uint16_t next;
> };
>
> struct virtqueue {
> @@ -245,9 +246,19 @@ struct virtio_tx_region {
> __attribute__((__aligned__(16)));
> };
>
> +static inline void
> +vring_desc_init_packed(struct vring *vr, int n)
> +{
> + int i;
> + for (i = 0; i < n; i++) {
> + struct vring_desc_packed *desc = &vr->desc_packed[i];
> + desc->index = i;
> + }
> +}
I see the split variant is also called to init the indirect tables.
Do you confirm this isn't needed in the case of packed ring?
> +
> /* Chain all the descriptors in the ring with an END */
> static inline void
> -vring_desc_init(struct vring_desc *dp, uint16_t n)
> +vring_desc_init_split(struct vring_desc *dp, uint16_t n)
> {
> uint16_t i;
>
>
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