linux-kernel - [PATCH net-next 2/7] net: ipa: zero unused portions of filter table memory

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Message-Id: <20211124202511.862588-3-elder@linaro.org>
Date:   Wed, 24 Nov 2021 14:25:06 -0600
From:   Alex Elder <elder@...aro.org>
To:     davem@...emloft.net, kuba@...nel.org
Cc:     pkurapat@...eaurora.org, avuyyuru@...eaurora.org,
        bjorn.andersson@...aro.org, cpratapa@...eaurora.org,
        subashab@...eaurora.org, evgreen@...omium.org, elder@...nel.org,
        netdev@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH net-next 2/7] net: ipa: zero unused portions of filter table memory

Not all filter table entries are used.  Only certain endpoints
support filtering, and the table begins with a bitmap indicating
which endpoints use the "slots" that follow for filter rules.

Currently, unused filter table entries are not initialized.
Instead, zero-fill the entire unused portion of the filter table
memory regions, to make it more obvious that memory is unused (and
not subsequently modified).

This is not strictly necessary, but the result is reassuring when
looking at filter table memory.

Signed-off-by: Alex Elder <elder@...aro.org>
---
 drivers/net/ipa/ipa_table.c | 48 +++++++++++++++++++++++++++++++------
 1 file changed, 41 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ipa/ipa_table.c b/drivers/net/ipa/ipa_table.c
index 1da334f54944a..2f5a58bfc529a 100644
--- a/drivers/net/ipa/ipa_table.c
+++ b/drivers/net/ipa/ipa_table.c
@@ -419,21 +419,26 @@ static void ipa_table_init_add(struct gsi_trans *trans, bool filter,
 	const struct ipa_mem *mem = ipa_mem_find(ipa, mem_id);
 	dma_addr_t hash_addr;
 	dma_addr_t addr;
+	u32 zero_offset;
 	u16 hash_count;
+	u32 zero_size;
 	u16 hash_size;
 	u16 count;
 	u16 size;
 
-	/* The number of filtering endpoints determines number of entries
-	 * in the filter table.  The hashed and non-hashed filter table
-	 * will have the same number of entries.  The size of the route
-	 * table region determines the number of entries it has.
-	 */
+	/* Compute the number of table entries to initialize */
 	if (filter) {
-		/* Include one extra "slot" to hold the filter map itself */
+		/* The number of filtering endpoints determines number of
+		 * entries in the filter table; we also add one more "slot"
+		 * to hold the bitmap itself.  The size of the hashed filter
+		 * table is either the same as the non-hashed one, or zero.
+		 */
 		count = 1 + hweight32(ipa->filter_map);
 		hash_count = hash_mem->size ? count : 0;
 	} else {
+		/* The size of a route table region determines the number
+		 * of entries it has.
+		 */
 		count = mem->size / sizeof(__le64);
 		hash_count = hash_mem->size / sizeof(__le64);
 	}
@@ -445,13 +450,42 @@ static void ipa_table_init_add(struct gsi_trans *trans, bool filter,
 
 	ipa_cmd_table_init_add(trans, opcode, size, mem->offset, addr,
 			       hash_size, hash_mem->offset, hash_addr);
+	if (!filter)
+		return;
+
+	/* Zero the unused space in the filter table */
+	zero_offset = mem->offset + size;
+	zero_size = mem->size - size;
+	ipa_cmd_dma_shared_mem_add(trans, zero_offset, zero_size,
+				   ipa->zero_addr, true);
+	if (!hash_size)
+		return;
+
+	/* Zero the unused space in the hashed filter table */
+	zero_offset = hash_mem->offset + hash_size;
+	zero_size = hash_mem->size - hash_size;
+	ipa_cmd_dma_shared_mem_add(trans, zero_offset, zero_size,
+				   ipa->zero_addr, true);
 }
 
 int ipa_table_setup(struct ipa *ipa)
 {
 	struct gsi_trans *trans;
 
-	trans = ipa_cmd_trans_alloc(ipa, 4);
+	/* We will need at most 8 TREs:
+	 * - IPv4:
+	 *     - One for route table initialization (non-hashed and hashed)
+	 *     - One for filter table initialization (non-hashed and hashed)
+	 *     - One to zero unused entries in the non-hashed filter table
+	 *     - One to zero unused entries in the hashed filter table
+	 * - IPv6:
+	 *     - One for route table initialization (non-hashed and hashed)
+	 *     - One for filter table initialization (non-hashed and hashed)
+	 *     - One to zero unused entries in the non-hashed filter table
+	 *     - One to zero unused entries in the hashed filter table
+	 * All platforms support at least 8 TREs in a transaction.
+	 */
+	trans = ipa_cmd_trans_alloc(ipa, 8);
 	if (!trans) {
 		dev_err(&ipa->pdev->dev, "no transaction for table setup\n");
 		return -EBUSY;
-- 
2.32.0