linux-kernel - [PATCH 5.10 094/141] net: ipa: fix table alignment requirement

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Date:   Mon, 26 Sep 2022 12:12:00 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Alex Elder <elder@...aro.org>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 094/141] net: ipa: fix table alignment requirement

From: Alex Elder <elder@...aro.org>

[ Upstream commit e5d4e96b44cf20330c970c3e30ea0a8c3a23feca ]

We currently have a build-time check to ensure that the minimum DMA
allocation alignment satisfies the constraint that IPA filter and
route tables must point to rules that are 128-byte aligned.

But what's really important is that the actual allocated DMA memory
has that alignment, even if the minimum is smaller than that.

Remove the BUILD_BUG_ON() call checking against minimim DMA alignment
and instead verify at rutime that the allocated memory is properly
aligned.

Signed-off-by: Alex Elder <elder@...aro.org>
Signed-off-by: David S. Miller <davem@...emloft.net>
Stable-dep-of: cf412ec33325 ("net: ipa: properly limit modem routing table use")
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/ipa/ipa_table.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ipa/ipa_table.c b/drivers/net/ipa/ipa_table.c
index f26cb9d706da..45e1d68b4694 100644
--- a/drivers/net/ipa/ipa_table.c
+++ b/drivers/net/ipa/ipa_table.c
@@ -118,14 +118,6 @@
 /* Check things that can be validated at build time. */
 static void ipa_table_validate_build(void)
 {
-	/* IPA hardware accesses memory 128 bytes at a time.  Addresses
-	 * referred to by entries in filter and route tables must be
-	 * aligned on 128-byte byte boundaries.  The only rule address
-	 * ever use is the "zero rule", and it's aligned at the base
-	 * of a coherent DMA allocation.
-	 */
-	BUILD_BUG_ON(ARCH_DMA_MINALIGN % IPA_TABLE_ALIGN);
-
 	/* Filter and route tables contain DMA addresses that refer
 	 * to filter or route rules.  But the size of a table entry
 	 * is 64 bits regardless of what the size of an AP DMA address
@@ -669,6 +661,18 @@ int ipa_table_init(struct ipa *ipa)
 	if (!virt)
 		return -ENOMEM;
 
+	/* We put the "zero rule" at the base of our table area.  The IPA
+	 * hardware requires rules to be aligned on a 128-byte boundary.
+	 * Make sure the allocation satisfies this constraint.
+	 */
+	if (addr % IPA_TABLE_ALIGN) {
+		dev_err(dev, "table address %pad not %u-byte aligned\n",
+			&addr, IPA_TABLE_ALIGN);
+		dma_free_coherent(dev, size, virt, addr);
+
+		return -ERANGE;
+	}
+
 	ipa->table_virt = virt;
 	ipa->table_addr = addr;
 
-- 
2.35.1