linux-kernel - Re: [RFC PATCH v2 1/1] Providers/rxe: Add dma-buf support

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Date:   Thu, 30 Sep 2021 20:24:46 +0900
From:   Shunsuke Mie <mie@...l.co.jp>
To:     Zhu Yanjun <zyjzyj2000@...il.com>
Cc:     Christian König <christian.koenig@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Jianxin Xiong <jianxin.xiong@...el.com>,
        Leon Romanovsky <leon@...nel.org>,
        Maor Gottlieb <maorg@...dia.com>,
        Sean Hefty <sean.hefty@...el.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
        linux-media@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        RDMA mailing list <linux-rdma@...r.kernel.org>,
        Damian Hobson-Garcia <dhobsong@...l.co.jp>,
        Takanari Hayama <taki@...l.co.jp>,
        Tomohito Esaki <etom@...l.co.jp>
Subject: Re: [RFC PATCH v2 1/1] Providers/rxe: Add dma-buf support

2021年9月30日(木) 20:18 Zhu Yanjun <zyjzyj2000@...il.com>:
>
> On Thu, Sep 30, 2021 at 7:06 PM Shunsuke Mie <mie@...l.co.jp> wrote:
> >
> > 2021年9月30日(木) 16:23 Zhu Yanjun <zyjzyj2000@...il.com>:
> > >
> > > On Thu, Sep 30, 2021 at 2:58 PM Shunsuke Mie <mie@...l.co.jp> wrote:
> > > >
> > > > 2021年9月30日(木) 15:37 Zhu Yanjun <zyjzyj2000@...il.com>:
> > > > >
> > > > > On Thu, Sep 30, 2021 at 2:20 PM Shunsuke Mie <mie@...l.co.jp> wrote:
> > > > > >
> > > > > > Implement a new provider method for dma-buf base memory registration.
> > > > > >
> > > > > > Signed-off-by: Shunsuke Mie <mie@...l.co.jp>
> > > > > > ---
> > > > > >  providers/rxe/rxe.c | 21 +++++++++++++++++++++
> > > > > >  1 file changed, 21 insertions(+)
> > > > > >
> > > > > > diff --git a/providers/rxe/rxe.c b/providers/rxe/rxe.c
> > > > > > index 3c3ea8bb..84e00e60 100644
> > > > > > --- a/providers/rxe/rxe.c
> > > > > > +++ b/providers/rxe/rxe.c
> > > > > > @@ -239,6 +239,26 @@ static struct ibv_mr *rxe_reg_mr(struct ibv_pd *pd, void *addr, size_t length,
> > > > > >         return &vmr->ibv_mr;
> > > > > >  }
> > > > > >
> > > > > > +static struct ibv_mr *rxe_reg_dmabuf_mr(struct ibv_pd *pd, uint64_t offset,
> > > > > > +                                       size_t length, uint64_t iova, int fd,
> > > > > > +                                       int access)
> > > > > > +{
> > > > > > +       struct verbs_mr *vmr;
> > > > > > +       int ret;
> > > > > > +
> > > > > > +       vmr = malloc(sizeof(*vmr));
> > > > > > +       if (!vmr)
> > > > > > +               return NULL;
> > > > > > +
> > > > >
> > > > > Do we need to set vmr to zero like the following?
> > > > >
> > > > > memset(vmr, 0, sizeof(*vmr));
> > > > >
> > > > > Zhu Yanjun
> > > > Thank you for your quick response.
> > > >
> > > > I think it is better to clear the vmr. Actually the mlx5 driver allocates
> > > > the vmr using calloc().
> > > >
> > > > In addition, rxe_reg_mr() (not rxe_reg_dmabuf_mr()) is used the malloc
> > > > and not clear the vmr. I think It has to be fixed too. Should I make
> > > > another patch to fix this problem?
> > >
> > > Yes. Please.
> > >
> > > Zhu Yanjun
> > >
> > > >
> > > > Thanks a lot.
> > > > Shunsuke
> > > >
> > > > ~
> >
> > I looked into the vmr more, but there was no need to clear it. Moreover,
> > some implementations also use malloc without memory clear.
> >
>
> I confronted a lot of problems with memory not initialization.
> And a latest bug is https://www.spinics.net/lists/linux-rdma/msg105001.html
>
> So it is a good habit to clear a newly allocated memory.
>
> Zhu Yanjun
>
> > Thanks,
> > Shunsuke
Ok, I understand that thought. I'll send a patch.

Shunsuke.