[PATCH net v3 1/2] bnge: cap RSS contexts and RX rings to the RSS table size

[Vikas Gupta <vikas.gupta@broadcom.com>]

From: Dharmender Garg <dharmender.garg@broadcom.com>

The hardware supports at most BNGE_RSS_TABLE_MAX_TBL (8) RSS contexts.
They are stored in vnic->fw_rss_cos_lb_ctx[8] and back a 512-entry
(BNGE_MAX_RSS_TABLE_ENTRIES) indirection table and DMA buffer, so at
most 512 RX rings can be served by RSS.

bnge_cal_nr_rss_ctxs() has no upper bound, so with more RX rings it
returns more than 8 contexts: bnge_setup_vnic() writes past
fw_rss_cos_lb_ctx[], bnge_set_dflt_rss_indir_tbl() and
bnge_fill_hw_rss_tbl() write past the indirection table and its DMA
buffer, and the pad computation in bnge_set_dflt_rss_indir_tbl()
underflows into a huge memset().

Cap the number of contexts at BNGE_RSS_TABLE_MAX_TBL and the number
of RX rings at BNGE_MAX_RSS_TABLE_ENTRIES, so the sizes derived from
the ring count always fit the arrays.

Fixes: 627c67f038d2 ("bng_en: Add resource management support")
Signed-off-by: Dharmender Garg <dharmender.garg@broadcom.com>
Reviewed-by: Vikas Gupta <vikas.gupta@broadcom.com>
---
 drivers/net/ethernet/broadcom/bnge/bnge_resc.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bnge/bnge_resc.c b/drivers/net/ethernet/broadcom/bnge/bnge_resc.c
index 4711dd4945ff..b540eed12fc6 100644
--- a/drivers/net/ethernet/broadcom/bnge/bnge_resc.c
+++ b/drivers/net/ethernet/broadcom/bnge/bnge_resc.c
@@ -182,8 +182,9 @@ int bnge_cal_nr_rss_ctxs(u16 rx_rings)
 	if (!rx_rings)
 		return 0;
 
-	return bnge_adjust_pow_two(rx_rings - 1,
-				   BNGE_RSS_TABLE_ENTRIES);
+	return min_t(int, bnge_adjust_pow_two(rx_rings - 1,
+					      BNGE_RSS_TABLE_ENTRIES),
+		     BNGE_RSS_TABLE_MAX_TBL);
 }
 
 static u16 bnge_rss_ctxs_in_use(struct bnge_dev *bd,
@@ -459,6 +460,7 @@ static void _bnge_get_max_rings(struct bnge_dev *bd, u16 *max_rx,
 	}
 
 	*max_rx = min_t(int, *max_rx, max_ring_grps);
+	*max_rx = min_t(int, *max_rx, BNGE_MAX_RSS_TABLE_ENTRIES);
 }
 
 static int bnge_get_max_rings(struct bnge_dev *bd, u16 *max_rx,
-- 
2.52.0