On Mon, Aug 19, 2019 at 05:39:04PM +0000, Bernard Metzler wrote: > > >To: "Bernard Metzler" <BMT@xxxxxxxxxxxxxx> > >From: "Jason Gunthorpe" <jgg@xxxxxxxx> > >Date: 08/19/2019 06:35PM > >Cc: "Geert Uytterhoeven" <geert@xxxxxxxxxxxxxx>, "Doug Ledford" > ><dledford@xxxxxxxxxx>, linux-rdma@xxxxxxxxxxxxxxx, > >linux-kernel@xxxxxxxxxxxxxxx > >Subject: [EXTERNAL] Re: Re: Re: Re: Re: [PATCH] RDMA/siw: Fix > >compiler warnings on 32-bit due to u64/pointer abuse > > > >On Mon, Aug 19, 2019 at 04:29:11PM +0000, Bernard Metzler 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, > >> >linux-kernel@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. > > > >Oh gross, it overloads the IOVA in the WR with a kernel void * ?? > > Oh no. The user library writes the buffer address into > the 64bit address field of the WR. This is nothing siw > has invented. No HW provider sticks pointers into the WR ring. It is either an iova & lkey pair, or SGE information is inlined into the WR ring. Never, ever, a user or kernel pointer. The closest we get to a kernel pointer is with the local dma lkey & iova == physical memory address. > >Why does siw_pbl_get_buffer not return a void *?? > > > I think, in fact, it should be dma_addr_t, since this is > what PBL's are described with. Makes sense? You mean because siw uses dma_virt_ops and can translate a dma_addr_t back to a pfn? Yes, that would make alot more sense. If all conversions went explicitly from a iova & lkey -> dma_addr_t -> void * in the kmap then I'd be a lot happier Jason
