[PATCH 1/2] virtio.txt: add MQ support

converted to tex in the next patch  Signed-off-by: Michael S. Tsirkin <> ---  virtio-v1.0-wd01-part1-specification.txt
86 +++++++++++++++++++++++++++++---  1 file changed, 78 insertions(+), 8 deletions(-)  diff --git a/virtio-v1.0-wd01-part1-specification.txt b/virtio-v1.0-wd01-part1-specification.txt index ba3ecae..b63bda6 100644 --- a/virtio-v1.0-wd01-part1-specification.txt +++ b/virtio-v1.0-wd01-part1-specification.txt @@ -2309,9 +2309,12 @@ features.  2.4.1.2. Virtqueues

------------------

- 0:receiveq. 1:transmitq. 2:controlq + 0:receiveq0. 1:transmitq0. .... 2N:receivqN. 2N+1: transmitqN. 2N+2:controlq
- Virtqueue 2 only exists if VIRTIO_NET_F_CTRL_VQ set. + N=0 if VIRTIO_NET_F_MQ is not negotiated, otherwise N is derived + from max_virtqueue_pairs control field. + + controlq only exists if VIRTIO_NET_F_CTRL_VQ set.
2.4.1.3. Feature bits

--------------------

@@ -2355,6 +2358,9 @@ features.
VIRTIO_NET_F_GUEST_ANNOUNCE(21) Guest can send gratuitous
packets.
+  VIRTIO_NET_F_MQ(22) Device supports multiqueue with automatic +
receive steering. +  2.4.1.3.1. Legacy Interface: Feature bits

--------------------

VIRTIO_NET_F_GSO (6) Device handles packets with any GSO type. @@ -2366,7 +2372,7 @@ were required.  100.4.1.4. Device configuration layout

---------------------

-Two configuration fields are currently defined. The mac address field +Three configuration fields are currently defined. The mac address field  always exists (though is only valid if VIRTIO_NET_F_MAC is set), and  the status field only exists if VIRTIO_NET_F_STATUS is set. Two  read-only bits are currently defined for the status field: @@ -2375,9 +2381,17 @@ VIRTIO_NET_S_LINK_UP and VIRTIO_NET_S_ANNOUNCE.  	#define VIRTIO_NET_S_LINK_UP	1  	#define VIRTIO_NET_S_ANNOUNCE	2
+The following read-only field, max_virtqueue_pairs only exists if +VIRTIO_NET_F_MQ is set. This field specifies the maximum number +of each of transmit and receive virtqueues (receiveq0..receiveqN +and transmitq0..transmitqN respectively; + N=max_virtqueue_pairs - 1) that can be configured once VIRTIO_NET_F_MQ +is negotiated.  Legal values for this field are 1 to 0x8000. +  	struct virtio_net_config {  		u8 mac[6];  		le16 status; +		u16 max_virtqueue_pairs;  	};
100.4.1.4.1. Legacy Interface: Device configuration layout @@ -2390,7 +2404,9 @@ native endian of the guest rather than (necessarily) little-endian.

-----------------------------

1. The initialization routine should identify the receive and -  transmission virtqueues. +  transmission virtqueues, up to N+1 of each kind. If +  VIRTIO_NET_F_MQ feature bit is negotiated, +  N=max_virtqueue_pairs-1, otherwise identify N=0.
2. If the VIRTIO_NET_F_MAC feature bit is set, the configuration
space “mac” entry indicates the “physical” address of the the @@ -2405,7 +2421,15 @@ native endian of the guest rather than (necessarily) little-endian.
status can be read from the bottom bit of the “status” config
field. Otherwise, the link should be assumed active.
-5. The receive virtqueue should be filled with receive buffers. +5. Only receiveq0, transmitq0 and controlq are used by default. +  To use more queues driver must negotiate the VIRTIO_NET_F_MQ +  feature; initialize up to max_virtqueue_pairs of each of +  transmit and receive queues; +  execute_VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET command specifying the +  number of the transmit and receive queues that is going to be +  used and wait until the device consumes the controlq buffer and +  acks this command. +  The receive virtqueue should be filled with receive buffers.
This is described in detail below in “Setting Up Receive
Buffers”.
@@ -2433,9 +2457,10 @@ native endian of the guest rather than (necessarily) little-endian.  2.4.1.5. Device Operation

------------------------

-Packets are transmitted by placing them in the transmitq, and -buffers for incoming packets are placed in the receiveq. In each -case, the packet itself is preceeded by a header: +Packets are transmitted by placing them in the +transmitq0..transmitqN, and buffers for incoming packets are +placed in the receiveq0..receiveqN. In each case, the packet +itself is preceeded by a header:
	struct virtio_net_hdr {  	#define VIRTIO_NET_HDR_F_NEEDS_CSUM
1 @@ -2538,6 +2563,9 @@ buffer in the receive queue needs to be at least this length [20]  If VIRTIO_NET_F_MRG_RXBUF is negotiated, each buffer must be at  least the size of the struct virtio_net_hdr.
+If VIRTIO_NET_F_MQ is negotiated, each of receiveq0...receiveqN +that will be used should be populated with receive buffers. +  2.4.1.5.2.1. Packet Receive Interrupt

------------------------------------

@@ -2692,6 +2720,48 @@ Processing this notification involves:  2. Sending VIRTIO_NET_CTRL_ANNOUNCE_ACK command through control
vq.
+2.4.1.5.3.100. Automatic receive steering in multiqueue mode +

--------------------------

+ +If the driver negotiates the VIRTIO_NET_F_MQ feature bit (depends +on VIRTIO_NET_F_CTRL_VQ), it can transmit outgoing packets on one +of the multiple transmitq0..transmitqN and ask the device to +queue incoming packets into one the multiple receiveq0..receiveqN +depending on the packet flow. + +	struct virtio_net_ctrl_mq { +		u16 virtqueue_pairs; +	}; + +	#define VIRTIO_NET_CTRL_MQ
1 +	 #define VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET
0 +	 #define VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MIN
1 +	 #define VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MAX
0x8000 + +Multiqueue is disabled by default. Driver enables multiqueue by +executing the VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET command, specifying +the number of the transmit and receive queues that will be used; +thus transmitq0..transmitqn and receiveq0..receiveqn where +n=virtqueue_pairs-1 will be used. All these virtqueues must have +been pre-configured in advance. The range of legal values for the +virtqueue_pairs field is between 1 and max_virtqueue_pairs. + +When multiqueue is enabled, device uses automatic receive steering +based on packet flow.Programming of the receive steering +classificator is implicit. Transmitting a packet of a specific +flow on transmitqX will cause incoming packets for this flow to +be steered to receiveqX. For uni-directional protocols, or where +no packets have been transmitted yet, device will steer a packet +to a random queue out of the specified receiveq0..receiveqn. + +Multiqueue is disabled by setting virtqueue_pairs = 1 (this is +the default). After the command is consumed by the device, the +device will not steer new packets on virtqueues +receveq1..receiveqN (i.e. other than receiveq0) nor read from +transmitq1..transmitqN (i.e. other than transmitq0); accordingly, +driver should not transmit new packets on virtqueues other than +transmitq0. +  2.4.1.5.3.5. Offloads State Configuration

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MST