On Thu, Jun 11, 2020 at 02:11:51PM +0000, Bernard Metzler wrote:
>
> >To: "Bernard Metzler" <BMT@xxxxxxxxxxxxxx>
> >From: "Jason Gunthorpe" <jgg@xxxxxxxx>
> >Date: 06/11/2020 01:35PM
> >Cc: "Tom Seewald" <tseewald@xxxxxxxxx>, linux-rdma@xxxxxxxxxxxxxxx,
> >"Doug Ledford" <dledford@xxxxxxxxxx>
> >Subject: [EXTERNAL] Re: Re: [PATCH next] siw: Fix pointer-to-int-cast
> >warning in siw_rx_pbl()
> >
> >On Thu, Jun 11, 2020 at 10:21:49AM +0000, Bernard Metzler wrote:
> >>
> >> >To: "Tom Seewald" <tseewald@xxxxxxxxx>
> >> >From: "Jason Gunthorpe" <jgg@xxxxxxxx>
> >> >Date: 06/10/2020 07:50PM
> >> >Cc: linux-rdma@xxxxxxxxxxxxxxx, "Bernard Metzler"
> >> ><bmt@xxxxxxxxxxxxxx>, "Doug Ledford" <dledford@xxxxxxxxxx>
> >> >Subject: [EXTERNAL] Re: [PATCH next] siw: Fix pointer-to-int-cast
> >> >warning in siw_rx_pbl()
> >> >
> >> >On Wed, Jun 10, 2020 at 12:47:17PM -0500, Tom Seewald wrote:
> >> >> The variable buf_addr is type dma_addr_t, which may not be the
> >same
> >> >size
> >> >> as a pointer. To ensure it is the correct size, cast to a
> >> >uintptr_t.
> >> >>
> >> >> Signed-off-by: Tom Seewald <tseewald@xxxxxxxxx>
> >> >> drivers/infiniband/sw/siw/siw_qp_rx.c | 3 ++-
> >> >> 1 file changed, 2 insertions(+), 1 deletion(-)
> >> >>
> >> >> diff --git a/drivers/infiniband/sw/siw/siw_qp_rx.c
> >> >b/drivers/infiniband/sw/siw/siw_qp_rx.c
> >> >> index 650520244ed0..7271d705f4b0 100644
> >> >> +++ b/drivers/infiniband/sw/siw/siw_qp_rx.c
> >> >> @@ -139,7 +139,8 @@ static int siw_rx_pbl(struct siw_rx_stream
> >> >*srx, int *pbl_idx,
> >> >> break;
> >> >>
> >> >> bytes = min(bytes, len);
> >> >> - if (siw_rx_kva(srx, (void *)buf_addr, bytes) == bytes) {
> >> >> + if (siw_rx_kva(srx, (void *)(uintptr_t)buf_addr, bytes) ==
> >> >> + bytes) {
> >> >
> >> >How is a dma_addr_t being cast to a void *? That can't be right?
> >> >Bernard??
> >> >
> >> >Jason
> >> >
> >> Hi Tom, Hi Jason,
> >>
> >> Thanks for looking into that.
> >>
> >> siw_rx_kva() calls skb_copy_bits() to move data to its
> >> kernel clients destination. It expects a void * target
> >> address. This is why I chose it for siw_rx_kva() as well.
> >> One could say siw_rx_kva() should better get an uintptr_t
> >> as target argument, which would probably make it look
> >> more clean. And we rename it to siw_rx_kbuf(), and we
> >> cast from uintptr_t to (void *) just for
> >> skb_copy_bits(skb *, off, (void *)dest, len)
> >>
> >> This would avoid all those nasty (void *) casting at all (!)
> >> the places we are calling siw_rx_kva().
> >
> >But where did the dma_addr_t come from?
> >
> It initially comes from the scatterlist provided by the
> kernel user via drivers .map_mr_sg() method. There we get a
> dma_addr_t describing the users buffer.
For the SW dma maps you have to convert the dma_addr_t to a kva using
kmap, it cannot just be casted.
Jason
