netdev - [net-next PATCH 09/11] octeontx2-af: Allocate low priority entries for PF

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Date:   Tue, 17 Aug 2021 10:14:51 +0530
From:   Subbaraya Sundeep <sbhatta@...vell.com>
To:     <davem@...emloft.net>, <kuba@...nel.org>, <netdev@...r.kernel.org>
CC:     <sgoutham@...vell.com>, <hkelam@...vell.com>, <gakula@...vell.com>,
        Subbaraya Sundeep <sbhatta@...vell.com>
Subject: [net-next PATCH 09/11] octeontx2-af: Allocate low priority entries for PF

If the mcam entry allocation request is from PF
and NOT a priority allocation request then allocate
low priority entries so that PF entries always have
lower priority than its VFs. This is required so
that entries with (base) MCAM match criteria have lower
priority compared to entries with (base + additional)
match criteria. This patch considers only best case
scenario where PF entries are allocated from low
priority zone if low priority zone has free space.
There are worst case scenarios like:
1. VFs allocating hundreds of MCAM entries leading to VFs
using all mid priority zone and low priority zone entries
hence no entries free from low priority zone for PF.
2. All the PFs and VFs in the system allocating and freeing
entries causing fragmentation in MCAM space and all the
entries requested by PF could not fit in low priority
zone for allocation.
This patch do not handle worst case scenarios.

Signed-off-by: Subbaraya Sundeep <sbhatta@...vell.com>
Signed-off-by: Sunil Goutham <sgoutham@...vell.com>
---
 drivers/net/ethernet/marvell/octeontx2/af/rvu_npc.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/net/ethernet/marvell/octeontx2/af/rvu_npc.c b/drivers/net/ethernet/marvell/octeontx2/af/rvu_npc.c
index 52b2554..20a562c 100644
--- a/drivers/net/ethernet/marvell/octeontx2/af/rvu_npc.c
+++ b/drivers/net/ethernet/marvell/octeontx2/af/rvu_npc.c
@@ -2414,6 +2414,17 @@ static int npc_mcam_alloc_entries(struct npc_mcam *mcam, u16 pcifunc,
 		goto alloc;
 	}

+	/* For a VF base MCAM match rule is set by its PF. And all the
+	 * further MCAM rules installed by VF on its own are
+	 * concatenated with the base rule set by its PF. Hence PF entries
+	 * should be at lower priority compared to VF entries. Otherwise
+	 * base rule is hit always and rules installed by VF will be of
+	 * no use. Hence if the request is from PF and NOT a priority
+	 * allocation request then allocate low priority entries.
+	 */
+	if (!(pcifunc & RVU_PFVF_FUNC_MASK))
+		goto lprio_alloc;
+
 	/* Find out the search range for non-priority allocation request
 	 *
 	 * Get MCAM free entry count in middle zone.
@@ -2439,6 +2450,7 @@ static int npc_mcam_alloc_entries(struct npc_mcam *mcam, u16 pcifunc,
 		/* Not enough free entries, search all entries in reverse,
 		 * so that low priority ones will get used up.
 		 */
+lprio_alloc:
 		reverse = true;
 		start = 0;
 		end = mcam->bmap_entries;
-- 
2.7.4