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

[Jens Freimann]

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 <jfreim...@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)