Control messaging in multislot link layer flit
A link layer control message is generated and included in a flit that is to be sent over a serial data link to a device. The flits sent over the data link are to include a plurality of slots. Control messages can include, in some aspects, a viral alert message, a poison alert message, a credit return message, and acknowledgements.
1. An apparatus comprising:
I/O logic, implemented at least in part in hardware, to:
generate a link layer control message to be included in a flit that is to be sent over a serial data link to a device, wherein flits sent over the data link are to include a plurality of slots, and the plurality of slots enable encoding of a plurality of distinct headers in the flit; and
send the flit with the link layer control message.
2. The apparatus of claim 1 , wherein the I/O logic comprises a layered stack comprising physical layer logic, link layer logic, and protocol layer logic.
3. The apparatus of claim 1 , wherein the control message is to be encoded in a particular one of the slots and no other messages are to be included in the flit.
4. The apparatus of claim 3 , wherein the other slots are to be encoded as null slots.
5. The apparatus of claim 3 , wherein the control message is identifiable, at least in part, from an encoding of an opcode of the flit.
6. The apparatus of claim 3 , wherein the control message comprises a viral alert message.
7. The apparatus of claim 3 , wherein the control message comprises a poison alert message.
8. The apparatus of claim 1 , wherein the control message is to include at least one of credit returns and acknowledgements.
9. The apparatus of claim 8 , wherein the control message is to be encoded in a particular one of the plurality of slots, wherein the particular slot is the smallest of the plurality of slots.
10. The apparatus of claim 9 , wherein the plurality of slots consist of three defined slots.
11. The apparatus of claim 10 , wherein the particular slot is the third of the three slots, the first of the three slots comprises 72 bits, the second of the three slots comprises 70 bits, and the third slot comprises 18 bits.
12. The apparatus of claim 8 , wherein the control message includes dedicated bits for virtual network credit returns and dedicated bits for acknowledgement returns.
13. The apparatus of claim 12 , wherein the dedicated bits for credit returns comprise three bits adapted to be encoded with a credit return value between 0 and 7.
14. The apparatus of claim 12 , wherein the dedicated bits for credit returns comprise seven bits adapted to be encoded with a credit return value between 0 and 255.
15. The apparatus of claim 14 , wherein the credit returns comprises credit returns to a shared adaptive virtual network (VNA) credit pool.
16. An apparatus comprising:
I/O logic, implemented at least in part in hardware, to:
receive a flit over a serial data network, wherein the flit comprises a plurality of slots according to a defined flit format; and
identify a link layer control message from data encoded in a particular one of the plurality of slots of the flit, wherein the particular slot is the smallest of the plurality of slots, and the link layer control message is to include at least one of a credit return and an acknowledgement return.
17. The apparatus of claim 16 , wherein the control message is of a format including dedicated bits for virtual network credit returns and dedicated bits for acknowledgement returns.
18. A method comprising:
identifying a link layer control message to be sent to another device;
generating a flit to include the link layer control message, wherein the flit has a defined format defining a plurality of slots included in the flit, the plurality of slots enable encoding of a plurality of distinct headers in the flit, and the control message is to be encoded in at least one of the plurality of slots in the flit; and
sending the flit to the other device over a serial data link during a link transmitting state.
19. A system comprising:
a first device; and
a second device communicatively coupled to the first device using a serial data link, the second device including a link layer module executed by at least one processor to:
identify a link layer control message to be sent to the first device;
generate a flit to include the link layer control message, wherein the flit is to include a plurality of slots, the plurality of slots enable encoding of a plurality of distinct headers in the flit, and the control message is to be encoded in at least one of the plurality of slots in the flit; and
send the flit to the other device over a serial data link during a link transmitting state.
20. The system of claim 19 , wherein the first device comprises a microprocessor.
21. The system of claim 20 , wherein the second device comprises a second microprocessor.
22. The system of claim 20 , wherein the second device comprises a graphics accelerator.
23. The system of claim 19 , wherein the first device includes link layer logic to:
receive the flit over the data link;
identify the control message from the flit; and
process the control message.
24. An apparatus comprising:
I/O logic, implemented at least in part in hardware, to:
receive a flit over a serial data network, wherein the flit comprises a plurality of slots according to a defined flit format, and the plurality of slots enable encoding of a plurality of distinct headers in the flit; and
identify a link layer control message from data encoded in the flit.
25. The apparatus of claim 24 , wherein the control message comprises a viral alert message.
26. The apparatus of claim 24 , wherein the control message comprises a poison alert message.