patches for DPDK stable branches
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From: Wenwu Ma <wenwux.ma@intel.com>
To: dev@dpdk.org, fengchengwen@huawei.com
Cc: songx.jiale@intel.com, Wenwu Ma <wenwux.ma@intel.com>, stable@dpdk.org
Subject: [PATCH v3] dmadev: fix structure alignment
Date: Wed, 20 Mar 2024 15:23:32 +0800	[thread overview]
Message-ID: <20240320072332.1433526-1-wenwux.ma@intel.com> (raw)
In-Reply-To: <20240308053711.1260154-1-wenwux.ma@intel.com>

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")
Cc: stable@dpdk.org

Signed-off-by: Wenwu Ma <wenwux.ma@intel.com>
---
v2:
 - Because of performance drop, adjust the code to
   no longer demand cache line alignment
v3:
 - back to v1 patch

---
 lib/dmadev/rte_dmadev.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/lib/dmadev/rte_dmadev.c b/lib/dmadev/rte_dmadev.c
index 5953a77bd6..61e106d574 100644
--- a/lib/dmadev/rte_dmadev.c
+++ b/lib/dmadev/rte_dmadev.c
@@ -160,15 +160,25 @@ static int
 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: We do not call posix_memalign/aligned_alloc because it is
+	 * version dependent 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;
 }
-- 
2.25.1


  parent reply	other threads:[~2024-03-20  7:36 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-03-08  5:37 [PATCH] " Wenwu Ma
2024-03-08  7:01 ` fengchengwen
2024-03-15  1:43 ` [PATCH v2] " Wenwu Ma
2024-03-15  6:02   ` Tyler Retzlaff
2024-03-15  6:06   ` fengchengwen
2024-03-15  6:25     ` Ma, WenwuX
2024-03-15  7:44       ` Ma, WenwuX
2024-03-15  8:31         ` fengchengwen
2024-03-15  9:27           ` Ma, WenwuX
2024-03-20  4:11             ` fengchengwen
2024-03-20  7:34               ` Ma, WenwuX
2024-03-19  9:48   ` Jiale, SongX
2024-03-20  7:23 ` Wenwu Ma [this message]
2024-03-20  9:31   ` [PATCH v3] " fengchengwen
2024-06-27 12:46     ` Thomas Monjalon
2024-03-20 11:37   ` Thomas Monjalon
2024-03-21  1:25     ` Ma, WenwuX
2024-03-21  8:30       ` Thomas Monjalon
2024-03-21  8:57         ` Ma, WenwuX
2024-03-21  9:18         ` Ma, WenwuX
2024-03-21 10:06           ` Thomas Monjalon
2024-03-21 16:05             ` Tyler Retzlaff

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