Re: Re: Re: Re: Re: [PATCH] RDMA/siw: Fix compiler warnings on 32-bit due to u64/pointer abuse

From: Bernard Metzler
Date: Mon Aug 19 2019 - 12:29:22 EST

-----"Jason Gunthorpe" <jgg@xxxxxxxx> wrote: -----

>To: "Bernard Metzler" <BMT@xxxxxxxxxxxxxx>
>From: "Jason Gunthorpe" <jgg@xxxxxxxx>
>Date: 08/19/2019 06:05PM
>Cc: "Geert Uytterhoeven" <geert@xxxxxxxxxxxxxx>, "Doug Ledford"
><dledford@xxxxxxxxxx>, linux-rdma@xxxxxxxxxxxxxxx,
>Subject: [EXTERNAL] Re: Re: Re: Re: [PATCH] RDMA/siw: Fix compiler
>warnings on 32-bit due to u64/pointer abuse
>On Mon, Aug 19, 2019 at 03:54:56PM +0000, Bernard Metzler wrote:
>> Absolutely. But these addresses are conveyed through the
>> API as unsigned 64 during post_send(), and land in the siw
>> send queue as is. During send queue processing, these addresses
>> must be interpreted according to its context and transformed
>> (casted) back to the callers intention. I frankly do not
>> know what we can do differently... The representation of
>> all addresses as unsigned 64 is given. Sorry for the confusion.
>send work does not have pointers in it, so I'm confused what this is
>about. Does siw allow userspace to stick an ordinary pointer for the
>SG list?

Right a user references a buffer by address and local key it
got during reservation of that buffer. The user can provide any
VA between start of that buffer and registered length.

>The code paths here must be totally different, so there should be
>different types and functions for each case.

Yes, there is a function to process application memory (siw_rx_umem),
to process a kernel PBL (siw_rx_pbl), and one to process kernel
addresses (siw_rx_kva). Before running that function, the API
representation of the current SGE gets translated into target
buffer representation.

Thanks and best regards,