patch 'dmadev: fix structure alignment' has been queued to stable release 21.11.8

[Kevin Traynor]

Hi,

FYI, your patch has been queued to stable release 21.11.8

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 08/28/24. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the
patch applied to the branch. This will indicate if there was any rebasing
needed to apply to the stable branch. If there were code changes for rebasing
(ie: not only metadata diffs), please double check that the rebase was
correctly done.

Queued patches are on a temporary branch at:
https://github.com/kevintraynor/dpdk-stable

This queued commit can be viewed at:
https://github.com/kevintraynor/dpdk-stable/commit/2c3f6129d9d7aea65dc0c0e0c24cf3436af0abf3

Thanks.

Kevin

---
>From 2c3f6129d9d7aea65dc0c0e0c24cf3436af0abf3 Mon Sep 17 00:00:00 2001
From: Wenwu Ma <wenwux.ma at intel.com>
Date: Wed, 20 Mar 2024 15:23:32 +0800
Subject: [PATCH] dmadev: fix structure alignment

[ upstream commit c15902587b538ff02cfb0fbb4dd481f1503d936b ]

The structure rte_dma_dev needs to be aligned to the cache line, but
the return value of malloc may not be aligned to the cache line. When
we use memset to clear the rte_dma_dev object, it may cause a segmentation
fault in clang-x86-platform.

This is because clang uses the "vmovaps" assembly instruction for
memset, which requires that the operands (rte_dma_dev objects) must
aligned on a 16-byte boundary or a general-protection exception (#GP)
is generated.

Therefore, either additional memory is applied for re-alignment, or the
rte_dma_dev object does not require cache line alignment. The patch
chooses the former option to fix the issue.

Fixes: b36970f2e13e ("dmadev: introduce DMA device library")

Signed-off-by: Wenwu Ma <wenwux.ma at intel.com>
Reviewed-by: Chengwen Feng <fengchengwen at huawei.com>
---
 lib/dmadev/rte_dmadev.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/lib/dmadev/rte_dmadev.c b/lib/dmadev/rte_dmadev.c
index d4b32b2971..4e2057d301 100644
--- a/lib/dmadev/rte_dmadev.c
+++ b/lib/dmadev/rte_dmadev.c
@@ -155,13 +155,22 @@ dma_dev_data_prepare(void)
 {
 	size_t size;
+	void *ptr;
 
 	if (rte_dma_devices != NULL)
 		return 0;
 
-	size = dma_devices_max * sizeof(struct rte_dma_dev);
-	rte_dma_devices = malloc(size);
-	if (rte_dma_devices == NULL)
+	/* The DMA device object is expected to align cacheline,
+	 * but the return value of malloc may not be aligned to the cache line.
+	 * Therefore, extra memory is applied for realignment.
+	 * Note: posix_memalign/aligned_alloc are not used
+	 * because not always available, depending on libc.
+	 */
+	size = dma_devices_max * sizeof(struct rte_dma_dev) + RTE_CACHE_LINE_SIZE;
+	ptr = malloc(size);
+	if (ptr == NULL)
 		return -ENOMEM;
-	memset(rte_dma_devices, 0, size);
+	memset(ptr, 0, size);
+
+	rte_dma_devices = RTE_PTR_ALIGN(ptr, RTE_CACHE_LINE_SIZE);
 
 	return 0;
-- 
2.46.0

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2024-08-23 17:18:11.532781881 +0100
+++ 0055-dmadev-fix-structure-alignment.patch	2024-08-23 17:18:09.719430102 +0100
@@ -1 +1 @@
-From c15902587b538ff02cfb0fbb4dd481f1503d936b Mon Sep 17 00:00:00 2001
+From 2c3f6129d9d7aea65dc0c0e0c24cf3436af0abf3 Mon Sep 17 00:00:00 2001
@@ -5,0 +6,2 @@
+[ upstream commit c15902587b538ff02cfb0fbb4dd481f1503d936b ]
+
@@ -21 +22,0 @@
-Cc: stable at dpdk.org
@@ -30 +31 @@
-index e64b279bac..845727210f 100644
+index d4b32b2971..4e2057d301 100644
@@ -33 +34 @@
-@@ -160,13 +160,22 @@ dma_dev_data_prepare(void)
+@@ -155,13 +155,22 @@ dma_dev_data_prepare(void)