linux-kernel - Re: [PATCH] RDMA/mlx5: return the EFAULT per ibv_advise

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Date:   Tue, 3 Aug 2021 20:56:54 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     Li Zhijian <lizhijian@...fujitsu.com>, dledford@...hat.com,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] RDMA/mlx5: return the EFAULT per ibv_advise_mr(3)

On Tue, Aug 03, 2021 at 01:25:07PM -0300, Jason Gunthorpe wrote:
> On Sun, Aug 01, 2021 at 05:20:50PM +0800, Li Zhijian wrote:
> > ibv_advise_mr(3) says:
> > EFAULT In one of the following: o When the range requested is out of the  MR  bounds,
> >        or  when  parts of it are not part of the process address space. o One of the
> >        lkeys provided in the scatter gather list is invalid or with wrong write access
> > 
> > Actually get_prefetchable_mr() will return NULL if it see above conditions
> 
> No, get_prefetchable_mr() returns NULL if the mkey is invalid

And what is this?
  1701 static struct mlx5_ib_mr *                         
  1702 get_prefetchable_mr(struct ib_pd *pd, enum ib_uverbs_advise_mr_advice advice,
  1703                     u32 lkey)

...

  1721         /* prefetch with write-access must be supported by the MR */
  1722         if (advice == IB_UVERBS_ADVISE_MR_ADVICE_PREFETCH_WRITE &&
  1723             !mr->umem->writable) {
  1724                 mr = NULL;
  1725                 goto end;
  1726         }


> 
> The above is talking about the address, which is checked inside
> pagefault_mr() and does return EFAULT for all the cases I can see?
> 
> Jason