[dpdk-dev] [PATCH v7 0/8] implement packed virtqueues

[dpdk-dev] [PATCH v7 0/8] implement packed virtqueues

[Jens Freimann]

I'm sending this out to get some comments especially on the TX path code. 

I added support for mergeable rx buffers, out of order processing and
indirect. The receive path works well but the TX path sometimes locks up
after a random number of packets transmitted, so please review this
patch extra careful. This is also why I didn't add any new performance
numbers to the cover letter yet.

To support out-of-order processing I used the vq_desc_extra struct to
add a .next field and use it as a list for managing descriptors. This
seemed to add less complexity to the code than adding a new data
structure to use as a list for packed queue descriptors. 

I also took out the patch for supporting virtio-user as it turned out
more complex than expected. I will try to get it working for the next
version, but if I don't can we add it in a later pach set (and then
probably not in 18.11?]

This is a basic implementation of packed virtqueues as specified in the
Virtio 1.1 draft. A compiled version of the current draft is available
at https://github.com/oasis-tcs/virtio-docs.git (or as .pdf at
https://github.com/oasis-tcs/virtio-docs/blob/master/virtio-v1.1-packed-wd10.pdf

A packed virtqueue is different from a split virtqueue in that it
consists of only a single descriptor ring that replaces available and
used ring, index and descriptor pointers.

Each descriptor is readable and writable and has a flags field. These flags
will mark if a descriptor is available or used.  To detect new available descriptors
even after the ring has wrapped, device and driver each have a
single-bit wrap counter that is flipped from 0 to 1 and vice versa every time
the last descriptor in the ring is used/made available.


Jens Freimann (8):
  net/virtio: vring init for packed queues
  net/virtio: add packed virtqueue defines
  net/virtio: add packed virtqueue helpers
  net/virtio: dump packed virtqueue data
  net/virtio: implement transmit path for packed queues
  net/virtio: implement receive path for packed queues
  net/virtio: add virtio send command packed queue support
  net/virtio: enable packed virtqueues by default

 drivers/net/virtio/virtio_ethdev.c | 161 +++++++--
 drivers/net/virtio/virtio_ethdev.h |   5 +
 drivers/net/virtio/virtio_pci.h    |   8 +
 drivers/net/virtio/virtio_ring.h   |  96 ++++-
 drivers/net/virtio/virtio_rxtx.c   | 544 ++++++++++++++++++++++++++++-
 drivers/net/virtio/virtqueue.c     |  23 ++
 drivers/net/virtio/virtqueue.h     |  52 ++-
 7 files changed, 846 insertions(+), 43 deletions(-)

-- 
2.17.1

[dpdk-dev] [PATCH v7 1/8] net/virtio: vring init for packed queues

[Jens Freimann]

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@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;
+			vq->vq_ring.desc_packed[i].index = i;
+		} 
+		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
 
 /*
  * 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;
+	}
+
 	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;
+	}
+}
+
 /* 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;
 
-- 
2.17.1

[dpdk-dev] [PATCH v7 2/8] net/virtio: add packed virtqueue defines

[Jens Freimann]

Signed-off-by: Jens Freimann <jfreimann@redhat.com>
---
 drivers/net/virtio/virtio_ring.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/virtio/virtio_ring.h b/drivers/net/virtio/virtio_ring.h
index 309069fdb..36a65f9b3 100644
--- a/drivers/net/virtio/virtio_ring.h
+++ b/drivers/net/virtio/virtio_ring.h
@@ -15,7 +15,11 @@
 #define VRING_DESC_F_WRITE      2
 /* This means the buffer contains a list of buffer descriptors. */
 #define VRING_DESC_F_INDIRECT   4
+/* This flag means the descriptor was made available by the driver */
 
+#define VRING_DESC_F_AVAIL(b)   ((uint16_t)(b) << 7)
+/* This flag means the descriptor was used by the device */
+#define VRING_DESC_F_USED(b)    ((uint16_t)(b) << 15)
 /* The Host uses this in used->flags to advise the Guest: don't kick me
  * when you add a buffer.  It's unreliable, so it's simply an
  * optimization.  Guest will still kick if it's out of buffers. */
-- 
2.17.1

[dpdk-dev] [PATCH v7 3/8] net/virtio: add packed virtqueue helpers

[Jens Freimann]

Add helper functions to set/clear and check descriptor flags.

Signed-off-by: Jens Freimann <jfreimann@redhat.com>
---
 drivers/net/virtio/virtio_ring.h | 26 ++++++++++++++++++++++++++
 drivers/net/virtio/virtqueue.h   | 11 +++++++++++
 2 files changed, 37 insertions(+)

diff --git a/drivers/net/virtio/virtio_ring.h b/drivers/net/virtio/virtio_ring.h
index 36a65f9b3..b9e63d4d4 100644
--- a/drivers/net/virtio/virtio_ring.h
+++ b/drivers/net/virtio/virtio_ring.h
@@ -78,6 +78,8 @@ struct vring_packed_desc_event {
 
 struct vring {
 	unsigned int num;
+	unsigned int avail_wrap_counter;
+	unsigned int used_wrap_counter;
 	union {
 		struct vring_desc_packed *desc_packed;
 		struct vring_desc *desc;
@@ -92,6 +94,30 @@ struct vring {
 	};
 };
 
+static inline void
+_set_desc_avail(struct vring_desc_packed *desc, int wrap_counter)
+{
+	desc->flags |= VRING_DESC_F_AVAIL(wrap_counter) |
+		       VRING_DESC_F_USED(!wrap_counter);
+}
+
+static inline void
+set_desc_avail(struct vring *vr, struct vring_desc_packed *desc)
+{
+	_set_desc_avail(desc, vr->avail_wrap_counter);
+}
+
+static inline int
+desc_is_used(struct vring_desc_packed *desc, struct vring *vr)
+{
+	uint16_t used, avail;
+
+	used = !!(desc->flags & VRING_DESC_F_USED(1));
+	avail = !!(desc->flags & VRING_DESC_F_AVAIL(1));
+
+	return used == avail && used == vr->used_wrap_counter;
+}
+
 /* The standard layout for the ring is a continuous chunk of memory which
  * looks like this.  We assume num is a power of 2.
  *
diff --git a/drivers/net/virtio/virtqueue.h b/drivers/net/virtio/virtqueue.h
index 6a4f92b79..b55ace958 100644
--- a/drivers/net/virtio/virtqueue.h
+++ b/drivers/net/virtio/virtqueue.h
@@ -246,6 +246,17 @@ struct virtio_tx_region {
 			   __attribute__((__aligned__(16)));
 };
 
+static inline uint16_t
+update_pq_avail_index(struct virtqueue *vq)
+{
+	if (++vq->vq_avail_idx >= vq->vq_nentries) {
+		vq->vq_avail_idx = 0;
+		vq->vq_ring.avail_wrap_counter ^= 1;
+	}
+
+	return vq->vq_avail_idx;
+}
+
 static inline void
 vring_desc_init_packed(struct vring *vr, int n)
 {
-- 
2.17.1

Re: [dpdk-dev] [PATCH v7 0/8] implement packed virtqueues

[Maxime Coquelin]

Hi Jens,

On 10/03/2018 03:11 PM, Jens Freimann wrote:
> To support out-of-order processing I used the vq_desc_extra struct to
> add a .next field and use it as a list for managing descriptors. This
> seemed to add less complexity to the code than adding a new data
> structure to use as a list for packed queue descriptors.

Looking at the series, I don't see a specific path when in-order has
been negotiated. Is it intended?
Wouldn't we save some cache misses when assuming packets are processed
in-order?

Maxime

Re: [dpdk-dev] [PATCH v7 0/8] implement packed virtqueues

[Jens Freimann]

On Wed, Oct 03, 2018 at 03:11:10PM +0200, Jens Freimann wrote:
>I'm sending this out to get some comments especially on the TX path code.

Tested with this QEMU: https://github.com/jensfr/qemu/pull/new/wexu-packed-ring-v1-fixed

[dpdk-dev] [PATCH v7 0/8] implement packed virtqueues

[Jens Freimann]

I'm sending this out to get some comments especially on the TX path code. 

I added support for mergeable rx buffers, out of order processing and
indirect. The receive path works well but the TX path sometimes locks up
after a random number of packets transmitted, so please review this
patch extra careful. This is also why I didn't add any new performance
numbers to the cover letter yet.

To support out-of-order processing I used the vq_desc_extra struct to
add a .next field and use it as a list for managing descriptors. This
seemed to add less complexity to the code than adding a new data
structure to use as a list for packed queue descriptors. 

I also took out the patch for supporting virtio-user as it turned out
more complex than expected. I will try to get it working for the next
version, but if I don't can we add it in a later pach set (and then
probably not in 18.11?]

This is a basic implementation of packed virtqueues as specified in the
Virtio 1.1 draft. A compiled version of the current draft is available
at https://github.com/oasis-tcs/virtio-docs.git (or as .pdf at
https://github.com/oasis-tcs/virtio-docs/blob/master/virtio-v1.1-packed-wd10.pdf

A packed virtqueue is different from a split virtqueue in that it
consists of only a single descriptor ring that replaces available and
used ring, index and descriptor pointers.

Each descriptor is readable and writable and has a flags field. These flags
will mark if a descriptor is available or used.  To detect new available descriptors
even after the ring has wrapped, device and driver each have a
single-bit wrap counter that is flipped from 0 to 1 and vice versa every time
the last descriptor in the ring is used/made available.


Jens Freimann (8):
  net/virtio: vring init for packed queues
  net/virtio: add packed virtqueue defines
  net/virtio: add packed virtqueue helpers
  net/virtio: dump packed virtqueue data
  net/virtio: implement transmit path for packed queues
  net/virtio: implement receive path for packed queues
  net/virtio: add virtio send command packed queue support
  net/virtio: enable packed virtqueues by default

 drivers/net/virtio/virtio_ethdev.c | 161 +++++++--
 drivers/net/virtio/virtio_ethdev.h |   5 +
 drivers/net/virtio/virtio_pci.h    |   8 +
 drivers/net/virtio/virtio_ring.h   |  96 ++++-
 drivers/net/virtio/virtio_rxtx.c   | 544 ++++++++++++++++++++++++++++-
 drivers/net/virtio/virtqueue.c     |  23 ++
 drivers/net/virtio/virtqueue.h     |  52 ++-
 7 files changed, 846 insertions(+), 43 deletions(-)

-- 
2.17.1

[dpdk-dev] [PATCH v7 0/8] implement packed virtqueues

[Jens Freimann]

I'm sending this out to get some comments especially on the TX path code. 

I added support for mergeable rx buffers, out of order processing and
indirect. The receive path works well but the TX path sometimes locks up
after a random number of packets transmitted, so please review this
patch extra careful. This is also why I didn't add any new performance
numbers to the cover letter yet.

To support out-of-order processing I used the vq_desc_extra struct to
add a .next field and use it as a list for managing descriptors. This
seemed to add less complexity to the code than adding a new data
structure to use as a list for packed queue descriptors. 

I also took out the patch for supporting virtio-user as it turned out
more complex than expected. I will try to get it working for the next
version, but if I don't can we add it in a later pach set (and then
probably not in 18.11?]

This is a basic implementation of packed virtqueues as specified in the
Virtio 1.1 draft. A compiled version of the current draft is available
at https://github.com/oasis-tcs/virtio-docs.git (or as .pdf at
https://github.com/oasis-tcs/virtio-docs/blob/master/virtio-v1.1-packed-wd10.pdf

A packed virtqueue is different from a split virtqueue in that it
consists of only a single descriptor ring that replaces available and
used ring, index and descriptor pointers.

Each descriptor is readable and writable and has a flags field. These flags
will mark if a descriptor is available or used.  To detect new available descriptors
even after the ring has wrapped, device and driver each have a
single-bit wrap counter that is flipped from 0 to 1 and vice versa every time
the last descriptor in the ring is used/made available.


Jens Freimann (8):
  net/virtio: vring init for packed queues
  net/virtio: add packed virtqueue defines
  net/virtio: add packed virtqueue helpers
  net/virtio: dump packed virtqueue data
  net/virtio: implement transmit path for packed queues
  net/virtio: implement receive path for packed queues
  net/virtio: add virtio send command packed queue support
  net/virtio: enable packed virtqueues by default

 drivers/net/virtio/virtio_ethdev.c | 161 +++++++--
 drivers/net/virtio/virtio_ethdev.h |   5 +
 drivers/net/virtio/virtio_pci.h    |   8 +
 drivers/net/virtio/virtio_ring.h   |  96 ++++-
 drivers/net/virtio/virtio_rxtx.c   | 544 ++++++++++++++++++++++++++++-
 drivers/net/virtio/virtqueue.c     |  23 ++
 drivers/net/virtio/virtqueue.h     |  52 ++-
 7 files changed, 846 insertions(+), 43 deletions(-)

-- 
2.17.1