Re: [dpdk-dev] [PATCH v3 02/21] net/virtio: vring init for packed queues

[Jens Freimann <jfreimann@redhat.com>]

On Thu, Apr 05, 2018 at 04:15:56PM +0200, Maxime Coquelin wrote:
>
>
>On 04/05/2018 12:10 PM, Jens Freimann wrote:
>>Add and initialize descriptor data structures.
>>
>>Signed-off-by: Jens Freimann <jfreimann@redhat.com>
>>---
>>  drivers/net/virtio/virtio_ethdev.c | 22 +++++++++-------
>>  drivers/net/virtio/virtio_pci.h    |  8 ++++++
>>  drivers/net/virtio/virtio_ring.h   | 53 ++++++++++++++++++++++++++++++++++----
>>  drivers/net/virtio/virtqueue.h     | 10 +++++++
>>  4 files changed, 78 insertions(+), 15 deletions(-)
>>
>>diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
>>index 06fbf7311..cccefafe9 100644
>>--- a/drivers/net/virtio/virtio_ethdev.c
>>+++ b/drivers/net/virtio/virtio_ethdev.c
>>@@ -298,19 +298,21 @@ 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);
>>-	vq->vq_used_cons_idx = 0;
>>-	vq->vq_desc_head_idx = 0;
>>-	vq->vq_avail_idx = 0;
>>-	vq->vq_desc_tail_idx = (uint16_t)(vq->vq_nentries - 1);
>>+	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;
>>+	if (vtpci_packed_queue(vq->hw)) {
>>+		vring_desc_init_packed(vr, size);
>>+	} else {
>>+		vq->vq_desc_head_idx = 0;
>>+		vq->vq_desc_tail_idx = (uint16_t)(vq->vq_nentries - 1);
>>-	vring_desc_init(vr->desc, size);
>>+		vring_desc_init(vr->desc, size);
>>+	}
>>  	/*
>>  	 * Disable device(host) interrupting guest
>>@@ -385,7 +387,7 @@ 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);
>>diff --git a/drivers/net/virtio/virtio_pci.h b/drivers/net/virtio/virtio_pci.h
>>index a28ba8339..528fb46b9 100644
>>--- a/drivers/net/virtio/virtio_pci.h
>>+++ b/drivers/net/virtio/virtio_pci.h
>>@@ -112,6 +112,8 @@ 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
>>  /*
>>   * Some VirtIO feature bits (currently bits 28 through 31) are
>>@@ -304,6 +306,12 @@ 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..1bd7ba98e 100644
>>--- a/drivers/net/virtio/virtio_ring.h
>>+++ b/drivers/net/virtio/virtio_ring.h
>>@@ -9,6 +9,7 @@
>>  #include <rte_common.h>
>>+
>Remove new line
>
>>  /* This marks a buffer as continuing via the next field. */
>>  #define VRING_DESC_F_NEXT       1
>>  /* This marks a buffer as write-only (otherwise read-only). */
>>@@ -54,11 +55,38 @@ 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;
>>+};
>>+
>>+#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;
>>+	};
>
>Not a must, but I wonder if it wouldn't be cleaner to have a unique
>union of two structs, one for packed rings, and one for the legacy.
>I may be wrong, though.

I'm not sure either but this looked best to me. 

Thanks!

regards,
Jens 
>
>>  };
>>  /* The standard layout for the ring is a continuous chunk of memory which
>>@@ -95,10 +123,16 @@ 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 += 2 * 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 +142,19 @@ 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 *) (vr->driver_event +
>>+			sizeof(struct vring_packed_desc_event));
>>+		return;
>>+	}
>>+
>>  	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 14364f356..cc2e7c0f6 100644
>>--- a/drivers/net/virtio/virtqueue.h
>>+++ b/drivers/net/virtio/virtqueue.h
>>@@ -245,6 +245,16 @@ 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;
>>+	}
>>+}
>>+
>>  /* Chain all the descriptors in the ring with an END */
>>  static inline void
>>  vring_desc_init(struct vring_desc *dp, uint16_t n)
>>