On Thu, Jan 21, 2021 at 09:53:08AM +0000, David Laight wrote:
> From: Kevin Hao
> > Sent: 21 January 2021 07:09
> > 
> > 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.
> > 
> > Fixes: 7a36e4918e30 ("octeontx2-pf: Use the napi_alloc_frag() to alloc the pool buffers")
> > Reported-by: Subbaraya Sundeep <sbhatta@marvell.com>
> > Signed-off-by: Kevin Hao <haokexin@gmail.com>
> > ---
> >  drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
> > b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
> > index bdfa2e293531..5ddedc3b754d 100644
> > --- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
> > +++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
> > @@ -488,10 +488,11 @@ dma_addr_t __otx2_alloc_rbuf(struct otx2_nic *pfvf, struct otx2_pool *pool)
> >  	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);
> >  	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))) {
> > --
> > 2.29.2
> 
> Doesn't that break the 'free' code ?
> Surely it needs the original pointer.

Why do we care about the original pointer? The free code should work with
the mangling poiner. Did I miss something?

> 
> It isn't obvious that page_frag_free() it correct when the
> allocator is napi_alloc_frag() either.
> I'd have thought it ought to be returned to the pool.

Sorry, I didn't get what you mean. Could you elaborate a bit more?

Thanks,
Kevin

> 
> 	David
> 
> -
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