ice: Fix MSI-X vector fallback logic

The current MSI-X enablement logic tries to enable best-case MSI-X
vectors and if that fails we only support a bare-minimum set. This
includes a single MSI-X for 1 Tx and 1 Rx queue and a single MSI-X
for the OICR interrupt. Unfortunately, the driver fails to load when we
don't get as many MSI-X as requested for a couple reasons.

First, the code to allocate MSI-X in the driver tries to allocate
num_online_cpus() MSI-X for LAN traffic without caring about the number
of MSI-X actually enabled/requested from the kernel for LAN traffic.
So, when calling ice_get_res() for the PF VSI, it returns failure
because the number of available vectors is less than requested. Fix
this by not allowing the PF VSI to allocation  more than
pf->num_lan_msix MSI-X vectors and pf->num_lan_msix Rx/Tx queues.
Limiting the number of queues is done because we don't want more than
1 Tx/Rx queue per interrupt due to performance conerns.

Second, the driver assigns pf->num_lan_msix = 2, to account for LAN
traffic and the OICR. However, pf->num_lan_msix is only meant for LAN
MSI-X. This is causing a failure when the PF VSI tries to
allocate/reserve the minimum pf->num_lan_msix because the OICR MSI-X has
already been reserved, so there may not be enough MSI-X vectors left.
Fix this by setting pf->num_lan_msix = 1 for the failure case. Then the
ICE_MIN_MSIX accounts for the LAN MSI-X and the OICR MSI-X needed for
the failure case.

Update the related defines used in ice_ena_msix_range() to align with
the above behavior and remove the unused RDMA defines because RDMA is
currently not supported. Also, remove the now incorrect comment.

Fixes: 152b978a ("ice: Rework ice_ena_msix_range")
Signed-off-by: Brett Creeley <brett.creeley@intel.com>
Tested-by: Tony Brelinski <tonyx.brelinski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/ice/ice.h

@@ -68,7 +68,9 @@
 #define ICE_INT_NAME_STR_LEN	(IFNAMSIZ + 16)
 #define ICE_AQ_LEN		64
 #define ICE_MBXSQ_LEN		64
-#define ICE_MIN_MSIX		2
+#define ICE_MIN_LAN_TXRX_MSIX	1
+#define ICE_MIN_LAN_OICR_MSIX	1
+#define ICE_MIN_MSIX		(ICE_MIN_LAN_TXRX_MSIX + ICE_MIN_LAN_OICR_MSIX)
 #define ICE_FDIR_MSIX		1
 #define ICE_NO_VSI		0xffff
 #define ICE_VSI_MAP_CONTIG	0

drivers/net/ethernet/intel/ice/ice_lib.c

@@ -161,8 +161,9 @@ static void ice_vsi_set_num_qs(struct ice_vsi *vsi, u16 vf_id)
 
 	switch (vsi->type) {
 	case ICE_VSI_PF:
-		vsi->alloc_txq = min_t(int, ice_get_avail_txq_count(pf),
-				       num_online_cpus());
+		vsi->alloc_txq = min3(pf->num_lan_msix,
+				      ice_get_avail_txq_count(pf),
+				      (u16)num_online_cpus());
 		if (vsi->req_txq) {
 			vsi->alloc_txq = vsi->req_txq;
 			vsi->num_txq = vsi->req_txq;
@@ -174,8 +175,9 @@ static void ice_vsi_set_num_qs(struct ice_vsi *vsi, u16 vf_id)
 		if (!test_bit(ICE_FLAG_RSS_ENA, pf->flags)) {
 			vsi->alloc_rxq = 1;
 		} else {
-			vsi->alloc_rxq = min_t(int, ice_get_avail_rxq_count(pf),
-					       num_online_cpus());
+			vsi->alloc_rxq = min3(pf->num_lan_msix,
+					      ice_get_avail_rxq_count(pf),
+					      (u16)num_online_cpus());
 			if (vsi->req_rxq) {
 				vsi->alloc_rxq = vsi->req_rxq;
 				vsi->num_rxq = vsi->req_rxq;
@@ -184,7 +186,9 @@ static void ice_vsi_set_num_qs(struct ice_vsi *vsi, u16 vf_id)
 
 		pf->num_lan_rx = vsi->alloc_rxq;
 
-		vsi->num_q_vectors = max_t(int, vsi->alloc_rxq, vsi->alloc_txq);
+		vsi->num_q_vectors = min_t(int, pf->num_lan_msix,
+					   max_t(int, vsi->alloc_rxq,
+						 vsi->alloc_txq));
 		break;
 	case ICE_VSI_VF:
 		vf = &pf->vf[vsi->vf_id];

drivers/net/ethernet/intel/ice/ice_main.c

@@ -3430,18 +3430,14 @@ static int ice_ena_msix_range(struct ice_pf *pf)
 	if (v_actual < v_budget) {
 		dev_warn(dev, "not enough OS MSI-X vectors. requested = %d, obtained = %d\n",
 			 v_budget, v_actual);
-/* 2 vectors each for LAN and RDMA (traffic + OICR), one for flow director */
-#define ICE_MIN_LAN_VECS 2
-#define ICE_MIN_RDMA_VECS 2
-#define ICE_MIN_VECS (ICE_MIN_LAN_VECS + ICE_MIN_RDMA_VECS + 1)
 
-		if (v_actual < ICE_MIN_LAN_VECS) {
+		if (v_actual < ICE_MIN_MSIX) {
 			/* error if we can't get minimum vectors */
 			pci_disable_msix(pf->pdev);
 			err = -ERANGE;
 			goto msix_err;
 		} else {
-			pf->num_lan_msix = ICE_MIN_LAN_VECS;
+			pf->num_lan_msix = ICE_MIN_LAN_TXRX_MSIX;
 		}
 	}