linux-kernel - Re: [PATCH RFC 1/2] RDMA/rxe: don't allow registering !PAGE

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Date:   Mon, 30 Oct 2023 08:13:27 +0000
From:   "Zhijian Li (Fujitsu)" <lizhijian@...itsu.com>
To:     Zhu Yanjun <yanjun.zhu@...ux.dev>,
        "zyjzyj2000@...il.com" <zyjzyj2000@...il.com>,
        "jgg@...pe.ca" <jgg@...pe.ca>, "leon@...nel.org" <leon@...nel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "rpearsonhpe@...il.com" <rpearsonhpe@...il.com>,
        "Daisuke Matsuda (Fujitsu)" <matsuda-daisuke@...itsu.com>,
        "bvanassche@....org" <bvanassche@....org>
Subject: Re: [PATCH RFC 1/2] RDMA/rxe: don't allow registering !PAGE_SIZE mr



On 27/10/2023 16:17, Zhu Yanjun wrote:
> 在 2023/10/27 13:41, Li Zhijian 写道:
>> 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.
> 
> When ULP uses folio or compound page, ULP can not work well with RXE after this commit is applied.
> 
> Perhaps removing page_size set in RXE is a good solution because page_size is set twice, firstly page_size is set in infiniband/core, secondly it is set in RXE.

Does The RXE one mean rxe_mr_init(), I think rxe_reg_user_mr() requires this.

  48 static void rxe_mr_init(int access, struct rxe_mr *mr)
  49 {
  50         u32 key = mr->elem.index << 8 | rxe_get_next_key(-1);
  51
  52         /* set ibmr->l/rkey and also copy into private l/rkey
  53          * for user MRs these will always be the same
  54          * for cases where caller 'owns' the key portion
  55          * they may be different until REG_MR WQE is executed.
  56          */
  57         mr->lkey = mr->ibmr.lkey = key;
  58         mr->rkey = mr->ibmr.rkey = key;
  59
  60         mr->access = access;
  61         mr->ibmr.page_size = PAGE_SIZE;
  62         mr->page_mask = PAGE_MASK;
  63         mr->page_shift = PAGE_SHIFT;
  64         mr->state = RXE_MR_STATE_INVALID;
  65 }


Thanks
Zhijian

> 
> When folio or compound page is used in ULP, it is very possible that page_size in infiniband/core is different from the page_size in RXE
> 
> Not sure what problem this difference will cause.
> 
> Zhu Yanjun
> 
>>
>> Signed-off-by: Li Zhijian <lizhijian@...itsu.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) {
>> +        rxe_info_mr(mr, "Unsupported MR with page_size %u, expect %lu\n",
>> +               page_size, PAGE_SIZE);
>> +        return -EOPNOTSUPP;
>> +    }
>> +
>>       mr->nbuf = 0;
>>       mr->page_shift = ilog2(page_size);
>>       mr->page_mask = ~((u64)page_size - 1);
>