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From: Thomas Monjalon <thomas@monjalon.net>
To: fengchengwen@huawei.com, Wenwu Ma <wenwux.ma@intel.com>
Cc: dev@dpdk.org, songx.jiale@intel.com, stable@dpdk.org
Subject: Re: [PATCH v3] dmadev: fix structure alignment
Date: Wed, 20 Mar 2024 12:37:16 +0100	[thread overview]
Message-ID: <3047329.687JKscXgg@thomas> (raw)
In-Reply-To: <20240320072332.1433526-1-wenwux.ma@intel.com>

20/03/2024 08:23, Wenwu Ma:
> 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>
[..]
> -	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);

Why not using aligned_alloc()?
https://en.cppreference.com/w/c/memory/aligned_alloc




  parent reply	other threads:[~2024-03-20 11:37 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 ` [PATCH v3] " Wenwu Ma
2024-03-20  9:31   ` fengchengwen
2024-06-27 12:46     ` Thomas Monjalon
2024-03-20 11:37   ` Thomas Monjalon [this message]
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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