virtio: support virtio 1.1 packed ring in vhost

virtio 1.1 defines a number of new features. Packed ring is among the most
notable and important one. It combines used, available, and descripptor rings
into one.

This patch provides experimental support for packed ring. To avoid
regression, when packed ring is configured for the interface, it is branched
to a separate RX and TX driver. Non packed ring should continue to perform
as it was before.

Packed ring is tested using qemu4.2 and ubuntu focal fossa (kernel 5.4.0-12)
on the guess VM which supports packed ring.

To configure VPP with packed ring, just add the optional keyword "packed"
when creating the vhost interface. To bring up the guest VM with packed ring,
add "packed=on" in the qemu launch command.

To facilitate troubleshooting, also added "verbose" option in
show vhost desc CLI to include displaying the indirect descriptors.

Known qemu reconnect issue -
If VPP is restarted, guest VMs also need to be restarted. The problem
is kernel virtio-net-pci keeps track of the previous available and used
indices. For virtio 1.0, these indices are in shared memory and qemu can
easily copy them to pass to the backend for reconnect. For virio 1.1, these
indices are no longer in shared memory. Qemu needs a new mechanism to retrieve
them and it is not currently implemented. So when the protocol reconnects,
qemu does not have the correct available and used indices to pass to the
backend. As a result, after the reconnect, virtio-net-pci is reading the TX
ring from the wrong position in the ring, not the same position which the
backend is writing. Similar problem exists also in the RX.

Type: feature

Signed-off-by: Steven Luong <sluong@cisco.com>
Change-Id: I5afc50b0bafab5a1de7a6dd10f399db3fafd144c

1 files changed, 55 insertions, 8 deletions

diff --git a/src/vnet/devices/virtio/vhost_user.h b/src/vnet/devices/virtio/vhost_user.h
index f14f26a71e4..b86f42e70e8 100644
--- a/src/vnet/devices/virtio/vhost_user.h
+++ b/src/vnet/devices/virtio/vhost_user.h
@@ -25,8 +25,15 @@
 
 #define VHOST_USER_VRING_NOFD_MASK      0x100
 #define VIRTQ_DESC_F_NEXT               1
+#define VIRTQ_DESC_F_WRITE              2
 #define VIRTQ_DESC_F_INDIRECT           4
-#define VHOST_USER_REPLY_MASK       (0x1 << 2)
+
+#define VIRTQ_DESC_F_AVAIL	        (1 << 7)
+#define VIRTQ_DESC_F_USED	        (1 << 15)
+
+#define VRING_EVENT_F_ENABLE            0x0
+#define VRING_EVENT_F_DISABLE           0x1
+#define VRING_EVENT_F_DESC              0x2
 
 #define VHOST_USER_PROTOCOL_F_MQ   0
 #define VHOST_USER_PROTOCOL_F_LOG_SHMFD	1
@@ -100,8 +107,11 @@ typedef enum
  _ (VHOST_F_LOG_ALL, 26)                \
  _ (VIRTIO_F_ANY_LAYOUT, 27)            \
  _ (VIRTIO_F_INDIRECT_DESC, 28)         \
+ _ (VIRTIO_F_EVENT_IDX, 29)		\
  _ (VHOST_USER_F_PROTOCOL_FEATURES, 30) \
- _ (VIRTIO_F_VERSION_1, 32)
+ _ (VIRTIO_F_VERSION_1, 32)             \
+ _ (VIRTIO_F_RING_PACKED, 34)           \
+ _ (VIRTIO_F_IN_ORDER, 35)
 
 typedef enum
 {
@@ -130,12 +140,12 @@ int vhost_user_create_if (vnet_main_t * vnm, vlib_main_t * vm,
 			  const char *sock_filename, u8 is_server,
 			  u32 * sw_if_index, u64 feature_mask,
 			  u8 renumber, u32 custom_dev_instance, u8 * hwaddr,
-			  u8 enable_gso);
+			  u8 enable_gso, u8 enable_packed);
 int vhost_user_modify_if (vnet_main_t * vnm, vlib_main_t * vm,
 			  const char *sock_filename, u8 is_server,
 			  u32 sw_if_index, u64 feature_mask,
 			  u8 renumber, u32 custom_dev_instance,
-			  u8 enable_gso);
+			  u8 enable_gso, u8 enable_packed);
 int vhost_user_delete_if (vnet_main_t * vnm, vlib_main_t * vm,
 			  u32 sw_if_index);
 
@@ -223,6 +233,22 @@ typedef struct
     } ring[VHOST_VRING_MAX_SIZE];
 } __attribute ((packed)) vring_used_t;
 
+typedef CLIB_PACKED (struct
+{
+  u64 addr;			// packet data buffer address
+  u32 len;			// packet data buffer size
+  u16 id;			// buffer id
+  u16 flags;			// flags
+}) vring_packed_desc_t;
+
+STATIC_ASSERT_SIZEOF (vring_packed_desc_t, 16);
+
+typedef CLIB_PACKED (struct
+{
+  u16 off_wrap;
+  u16 flags;
+}) vring_desc_event_t;
+
 typedef struct
 {
   u8 flags;
@@ -260,9 +286,21 @@ typedef struct
   u16 last_avail_idx;
   u16 last_used_idx;
   u16 n_since_last_int;
-  vring_desc_t *desc;
-  vring_avail_t *avail;
-  vring_used_t *used;
+  union
+  {
+    vring_desc_t *desc;
+    vring_packed_desc_t *packed_desc;
+  };
+  union
+  {
+    vring_avail_t *avail;
+    vring_desc_event_t *avail_event;
+  };
+  union
+  {
+    vring_used_t *used;
+    vring_desc_event_t *used_event;
+  };
   uword desc_user_addr;
   uword used_user_addr;
   uword avail_user_addr;
@@ -287,6 +325,9 @@ typedef struct
    * the interface even if it is disconnected and reconnected.
    */
   i16 qid;
+
+  u16 used_wrap_counter;
+  u16 avail_wrap_counter;
 } vhost_user_vring_t;
 
 #define VHOST_USER_EVENT_START_TIMER 1
@@ -332,6 +373,10 @@ typedef struct
   u16 *per_cpu_tx_qid;
 
   u8 enable_gso;
+
+  /* Packed ring configured */
+  u8 enable_packed;
+
 } vhost_user_intf_t;
 
 typedef struct
@@ -350,7 +395,6 @@ typedef struct
   virtio_net_hdr_mrg_rxbuf_t hdr; /** Virtio header **/
 } vhost_trace_t;
 
-
 #define VHOST_USER_RX_BUFFERS_N (2 * VLIB_FRAME_SIZE + 2)
 #define VHOST_USER_COPY_ARRAY_N (4 * VLIB_FRAME_SIZE)
 
@@ -365,6 +409,9 @@ typedef struct
   /* This is here so it doesn't end-up
    * using stack or registers. */
   vhost_trace_t *current_trace;
+
+  u32 *to_next_list;
+  vlib_buffer_t **rx_buffers_pdesc;
 } vhost_cpu_t;
 
 typedef struct