i40e: avoid divide by zero

In some weird circumstances with DCB enabled, the firmware can fail to
configure the VSI, leaving us with zero traffic classes. Check for this
state when we configure RSS to avoid a panic.

Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c
index e29d42c67fa913708c5a06a76b81915af0eb6a6c..db7dd812c1dfceadf066a3af39c1216949afc8c7 100644 (file)
--- a/drivers/net/ethernet/intel/i40e/i40e_main.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_main.c
@@ -10783,8 +10783,13 @@ static int i40e_pf_config_rss(struct i40e_pf *pf)
        /* Determine the RSS size of the VSI */
        if (!vsi->rss_size) {
                u16 qcount;
-
-               qcount = vsi->num_queue_pairs / vsi->tc_config.numtc;
+               /* If the firmware does something weird during VSI init, we
+                * could end up with zero TCs. Check for that to avoid
+                * divide-by-zero. It probably won't pass traffic, but it also
+                * won't panic.
+                */
+               qcount = vsi->num_queue_pairs /
+                        (vsi->tc_config.numtc ? vsi->tc_config.numtc : 1);
                vsi->rss_size = min_t(int, pf->alloc_rss_size, qcount);
        }
        if (!vsi->rss_size)