i40e: Fix interface init with MSI interrupts (no MSI-X)

[ Upstream commit 5fcbb71 ]

Fix the inability to bring an interface up on a setup with
only MSI interrupts enabled (no MSI-X).
Solution is to add a default number of QPs = 1. This is enough,
since without MSI-X support driver enables only a basic feature set.

Fixes: bc6d33c ("i40e: Fix the number of queues available to be mapped for use")
Signed-off-by: Dawid Lukwinski <dawid.lukwinski@intel.com>
Signed-off-by: Michal Maloszewski <michal.maloszewski@intel.com>
Tested-by: Dave Switzer <david.switzer@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Link: https://lore.kernel.org/r/20220722175401.112572-1-anthony.l.nguyen@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/net/ethernet/intel/i40e/i40e_main.c

@@ -1920,11 +1920,15 @@ static void i40e_vsi_setup_queue_map(struct i40e_vsi *vsi,
 		 * non-zero req_queue_pairs says that user requested a new
 		 * queue count via ethtool's set_channels, so use this
 		 * value for queues distribution across traffic classes
+		 * We need at least one queue pair for the interface
+		 * to be usable as we see in else statement.
 		 */
 		if (vsi->req_queue_pairs > 0)
 			vsi->num_queue_pairs = vsi->req_queue_pairs;
 		else if (pf->flags & I40E_FLAG_MSIX_ENABLED)
 			vsi->num_queue_pairs = pf->num_lan_msix;
+		else
+			vsi->num_queue_pairs = 1;
 	}
 
 	/* Number of queues per enabled TC */