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Date:   Mon, 30 Oct 2023 09:40:41 -0300
From:   Jason Gunthorpe <jgg@ziepe.ca>
To:     "Zhijian Li (Fujitsu)" <lizhijian@fujitsu.com>
Cc:     "zyjzyj2000@gmail.com" <zyjzyj2000@gmail.com>,
        "leon@kernel.org" <leon@kernel.org>,
        "linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "rpearsonhpe@gmail.com" <rpearsonhpe@gmail.com>,
        "Daisuke Matsuda (Fujitsu)" <matsuda-daisuke@fujitsu.com>,
        "bvanassche@acm.org" <bvanassche@acm.org>
Subject: Re: [PATCH RFC 1/2] RDMA/rxe: don't allow registering !PAGE_SIZE mr
Message-ID: <20231030124041.GE691768@ziepe.ca>
References: <20231027054154.2935054-1-lizhijian@fujitsu.com>
 <4da48f85-a72f-4f6b-900f-fc293d63b5ae@fujitsu.com>
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On Mon, Oct 30, 2023 at 07:51:41AM +0000, Zhijian Li (Fujitsu) wrote:
> 
> 
> On 27/10/2023 13:41, Li Zhijian wrote:
> > mr->page_list only encodes *page without page offset, when
> > page_size != PAGE_SIZE, we cannot restore the address with a wrong
> > page_offset.
> > 
> > Note that this patch will break some ULPs that try to register 4K
> > MR when PAGE_SIZE is not 4K.
> > SRP and nvme over RXE is known to be impacted.
> > 
> > Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
> > ---
> >   drivers/infiniband/sw/rxe/rxe_mr.c | 6 ++++++
> >   1 file changed, 6 insertions(+)
> > 
> > diff --git a/drivers/infiniband/sw/rxe/rxe_mr.c b/drivers/infiniband/sw/rxe/rxe_mr.c
> > index f54042e9aeb2..61a136ea1d91 100644
> > --- a/drivers/infiniband/sw/rxe/rxe_mr.c
> > +++ b/drivers/infiniband/sw/rxe/rxe_mr.c
> > @@ -234,6 +234,12 @@ int rxe_map_mr_sg(struct ib_mr *ibmr, struct scatterlist *sgl,
> >   	struct rxe_mr *mr = to_rmr(ibmr);
> >   	unsigned int page_size = mr_page_size(mr);
> >   
> > +	if (page_size != PAGE_SIZE) {
> 
> It seems this condition is too strict, it should be:
> 	if (!IS_ALIGNED(page_size, PAGE_SIZE))
> 
> So that, page_size with (N * PAGE_SIZE) can work as previously.
> Because the offset(mr.iova & page_mask) will get lost only when !IS_ALIGNED(page_size, PAGE_SIZE)

That makes sense

Jason