net: octeontx2: Make sure the buffer is 128 byte aligned

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(-)

Hi Kevin,

Tested at my end and works fine. Thanks for the patch.

Tested-by: Subbaraya Sundeep <sbhatta@marvell.com>

Sundeep

On Thu, Jan 21, 2021 at 12:51 PM Kevin Hao <haokexin@gmail.com> wrote:
>
> 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
>

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
> 
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)
>

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Thu, 21 Jan 2021 15:09:06 +0800 you wrote:
> 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>

> 

> [...]


Here is the summary with links:
  - net: octeontx2: Make sure the buffer is 128 byte aligned
    https://git.kernel.org/netdev/net/c/db2805150a0f

You are awesome, thank you!
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