On Sun, Feb 07, 2021 at 10:20:15AM +0100, Pavel Machek wrote: > Hi! > > > commit db2805150a0f27c00ad286a29109397a7723adad upstream. > > > > The octeontx2 hardware needs the buffer to be 128 byte aligned. > > But in the current implementation of napi_alloc_frag(), it can't > > guarantee the return address is 128 byte aligned even the request size > > is a multiple of 128 bytes, so we have to request an extra 128 bytes and > > use the PTR_ALIGN() to make sure that the buffer is aligned correctly. > > > > +++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c > > @@ -473,10 +473,11 @@ dma_addr_t __otx2_alloc_rbuf(struct otx2 > > dma_addr_t iova; > > u8 *buf; > > > > - buf = napi_alloc_frag(pool->rbsize); > > + buf = napi_alloc_frag(pool->rbsize + OTX2_ALIGN); > > if (unlikely(!buf)) > > return -ENOMEM; > > > > + buf = PTR_ALIGN(buf, OTX2_ALIGN); > > So we allocate a buffer, then change it, and then pass modified > pointer to the page_frag_free(buf); in the error path. That... can't > be right, right?
It doesn't matter. It will work as far as the address we passed to
page_frag_free()
is in the range of buf ~ (buf + rbsize).
>
> > iova = dma_map_single_attrs(pfvf->dev, buf, pool->rbsize,
> > DMA_FROM_DEVICE, DMA_ATTR_SKIP_CPU_SYNC);
> > if (unlikely(dma_mapping_error(pfvf->dev, iova))) {
>
> BTW otx2_alloc_rbuf and __otx2_alloc_rbuf should probably return s64,
> as they return negative error code...
It does seem buggy to return dma_addr_t for these two functions, I will cook up
a patch to fix this issue.
Thanks,
Kevin
>
> Best regards,
> Pavel
>
> --
> http://www.livejournal.com/~pavelmachek
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