[PATCH v3] dmadev: fix structure alignment
fengchengwen
fengchengwen at huawei.com
Wed Mar 20 10:31:14 CET 2024
Reviewed-by: Chengwen Feng <fengchengwen at huawei.com>
On 2024/3/20 15:23, Wenwu Ma wrote:
> 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 at dpdk.org
>
> Signed-off-by: Wenwu Ma <wenwux.ma at 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;
> }
>
More information about the stable
mailing list