From: Jonathan Matthew <jonathan@d14n.org>
Subject: mcx: remove MCX_MAX_QUEUES
To: tech@openbsd.org
Cc: bluhm@openbsd.org
Date: Tue, 18 Nov 2025 17:02:49 +1000

Now that we have IF_MAX_VECTORS as a limit on the number of queues an
interface will set up, MCX_MAX_QUEUES is kind of pointless - the
relevant limits are the size of the msi-x table and the maximum number of
event queues the nic will let us create.

This diff removes MCX_MAX_QUEUES, using IF_MAX_VECTORS instead where
appropriate, and adds the EQ limit to the calculation.  The EQ limit
might not ever be the limiting factor as generally the msi-x table is
smaller, but it's easy to account for it here.

ok?

Index: if_mcx.c
===================================================================
RCS file: /cvs/src/sys/dev/pci/if_mcx.c,v
diff -u -p -r1.120 if_mcx.c
--- if_mcx.c	11 Nov 2025 17:43:18 -0000	1.120
+++ if_mcx.c	18 Nov 2025 06:20:34 -0000
@@ -90,8 +90,6 @@ enum mcx_cmdq_slot {
 #define MCX_LOG_RQ_SIZE			10
 #define MCX_LOG_SQ_SIZE			11
 
-#define MCX_MAX_QUEUES			16
-
 /* completion event moderation - about 10khz, or 90% of the cq */
 #define MCX_CQ_MOD_PERIOD		50
 #define MCX_CQ_MOD_COUNTER		\
@@ -121,8 +119,8 @@ CTASSERT(ETHER_HDR_LEN + ETHER_VLAN_ENCA
 #define MCX_WQ_DOORBELL_BASE		MCX_PAGE_SIZE/2
 #define MCX_WQ_DOORBELL_STRIDE		64
 /* make sure the doorbells fit */
-CTASSERT(MCX_MAX_QUEUES * MCX_CQ_DOORBELL_STRIDE < MCX_WQ_DOORBELL_BASE);
-CTASSERT(MCX_MAX_QUEUES * MCX_WQ_DOORBELL_STRIDE <
+CTASSERT(IF_MAX_VECTORS * MCX_CQ_DOORBELL_STRIDE < MCX_WQ_DOORBELL_BASE);
+CTASSERT(IF_MAX_VECTORS * MCX_WQ_DOORBELL_STRIDE <
     MCX_DOORBELL_AREA_SIZE - MCX_WQ_DOORBELL_BASE);
 
 #define MCX_WQ_DOORBELL_MASK		0xffff
@@ -2482,6 +2480,7 @@ struct mcx_softc {
 
 	struct mcx_dmamem	 sc_doorbell_mem;
 
+	int			 sc_max_eqs;
 	struct mcx_eq		 sc_admin_eq;
 	struct mcx_eq		 sc_queue_eq;
 
@@ -2934,7 +2933,7 @@ mcx_attach(struct device *parent, struct
 
 	msix--; /* admin ops took one */
 	sc->sc_intrmap = intrmap_create(&sc->sc_dev, msix,
-	    MIN(MCX_MAX_QUEUES, IF_MAX_VECTORS), INTRMAP_POWEROF2);
+	    MIN(sc->sc_max_eqs, IF_MAX_VECTORS), INTRMAP_POWEROF2);
 	if (sc->sc_intrmap == NULL) {
 		printf(": unable to create interrupt map\n");
 		goto teardown;
@@ -4046,6 +4045,8 @@ mcx_hca_max_caps(struct mcx_softc *sc)
 	sc->sc_mhz = bemtoh32(&hca->device_frequency_mhz);
 	sc->sc_khz = bemtoh32(&hca->device_frequency_khz);
 
+	sc->sc_max_eqs = 1 << (hca->log_max_eq & MCX_CAP_DEVICE_LOG_MAX_EQ);
+
 free:
 	mcx_dmamem_free(sc, &mxm);
 
@@ -7303,7 +7304,7 @@ mcx_up(struct mcx_softc *sc)
 	struct mcx_flow_match match_crit;
 	struct mcx_rss_rule *rss;
 	uint32_t dest;
-	int rqns[MCX_MAX_QUEUES];
+	int rqns[IF_MAX_VECTORS];
 
 	if (mcx_create_tis(sc, &sc->sc_tis) != 0)
 		goto down;