-----"Jason Gunthorpe" <jgg@xxxxxxxx> 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.
Thanks,
Bernard.
