9.22. RX queue map register block

The RX queue map register block has a header with type 0x0000C090, version 0x00000200, and is used to control the mapping of packets into RX queues.

Address	Field	31..24	23..16	15..8	7..0	Reset value
RBB+0x00	Type	Vendor ID		Type		RO 0x0000C090
RBB+0x04	Version	Major	Minor	Patch	Meta	RO 0x00000200
RBB+0x08	Next pointer	Pointer to next register block				RO -
RBB+0x0C	Config			Tbl sz	Ports	RO -
RBB+0x10+16n	Port offset	Port indirection table offset				RO -
RBB+0x14+16n	Port RSS mask	Port RSS mask				RW 0x00000000
RBB+0x18+16n	Port app mask	Port app mask				RW 0x00000000

See Register blocks for definitions of the standard register block header fields.

There is one set of registers per port, with the source port for each packet determined by the tid field, which is set in the RX FIFO subsystem to identify the source port when data is aggregated from multiple ports. For each packet, the tdest field (provided by custom logic in the application section) and flow hash (computed in rx_hash in mqnic_ingress) are combined according to:

if (app_direct_enable[tid] && tdest[DEST_WIDTH-1]) begin
    queue_index = tdest;
end else begin
    queue_index = indir_table[tid][(tdest & app_mask[tid]) + (rss_hash & rss_mask[tid])];
end

The goal of this setup is to enable any combination of flow hashing and custom application logic to influence queue selection, under the direction of host software.

Config

The port count field contains information about the queue mapping configuration. The ports field contains the number of ports, while the table size field contains the log of the number of entries in the indirection table.

Address	31..24	23..16	15..8	7..0	Reset value
RBB+0x0C			Tbl sz	Ports	RO -

Port indirection table offset

The port indirection table offset field contains the offset to the start of the indirection table region, relative to the start of the current region. The indirection table itself is an array of 32-bit words, which should be loaded with the

Address	31..24	23..16	15..8	7..0	Reset value
RBB+0x10+16n	Port indirection table offset				RO -

Port RSS mask

The port RSS mask field contains a mask value to select a portion of the RSS flow hash.

Address	31..24	23..16	15..8	7..0	Reset value
RBB+0x14+16n	Port RSS mask				RW 0x00000000

Port app mask

The port app mask field contains a mask value to select a portion of the application-provided tdest value. Bit 31 of this register controls the application section’s ability to directly select a destination queue. If bit 31 is set, the application section can set the MSB of tdest to pass through the rest of tdest without modification.

Address	31..24	23..16	15..8	7..0	Reset value
RBB+0x18+16n	Port app mask				RW 0x00000000