21/03/2024 02:25, Ma, WenwuX:
> Hi, Thomas
>
> From: Thomas Monjalon <tho...@monjalon.net>
> > 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: sta...@dpdk.org
> > >
> > > Signed-off-by: Wenwu Ma <wenwux...@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
> >
> >
> because it is version dependent on libc.
Which libc is required?
