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From:   Shunsuke Mie <mie@igel.co.jp>
Date:   Thu, 30 Sep 2021 20:24:46 +0900
Message-ID: <CANXvt5qAesicr6m=YE0ZT4DMqo=MihfWfgdasXRJOhpnaKWbUA@mail.gmail.com>
Subject: Re: [RFC PATCH v2 1/1] Providers/rxe: Add dma-buf support
To:     Zhu Yanjun <zyjzyj2000@gmail.com>
Cc:     =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,
        Alex Deucher <alexander.deucher@amd.com>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        Doug Ledford <dledford@redhat.com>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        Jianxin Xiong <jianxin.xiong@intel.com>,
        Leon Romanovsky <leon@kernel.org>,
        Maor Gottlieb <maorg@nvidia.com>,
        Sean Hefty <sean.hefty@intel.com>,
        Sumit Semwal <sumit.semwal@linaro.org>,
        dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org,
        linux-media@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        RDMA mailing list <linux-rdma@vger.kernel.org>,
        Damian Hobson-Garcia <dhobsong@igel.co.jp>,
        Takanari Hayama <taki@igel.co.jp>,
        Tomohito Esaki <etom@igel.co.jp>
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2021=E5=B9=B49=E6=9C=8830=E6=97=A5(=E6=9C=A8) 20:18 Zhu Yanjun <zyjzyj2000@=
gmail.com>:
>
> On Thu, Sep 30, 2021 at 7:06 PM Shunsuke Mie <mie@igel.co.jp> wrote:
> >
> > 2021=E5=B9=B49=E6=9C=8830=E6=97=A5(=E6=9C=A8) 16:23 Zhu Yanjun <zyjzyj2=
000@gmail.com>:
> > >
> > > On Thu, Sep 30, 2021 at 2:58 PM Shunsuke Mie <mie@igel.co.jp> wrote:
> > > >
> > > > 2021=E5=B9=B49=E6=9C=8830=E6=97=A5(=E6=9C=A8) 15:37 Zhu Yanjun <zyj=
zyj2000@gmail.com>:
> > > > >
> > > > > On Thu, Sep 30, 2021 at 2:20 PM Shunsuke Mie <mie@igel.co.jp> wro=
te:
> > > > > >
> > > > > > Implement a new provider method for dma-buf base memory registr=
ation.
> > > > > >
> > > > > > Signed-off-by: Shunsuke Mie <mie@igel.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 ib=
v_pd *pd, void *addr, size_t length,
> > > > > >         return &vmr->ibv_mr;
> > > > > >  }
> > > > > >
> > > > > > +static struct ibv_mr *rxe_reg_dmabuf_mr(struct ibv_pd *pd, uin=
t64_t offset,
> > > > > > +                                       size_t length, uint64_t=
 iova, int fd,
> > > > > > +                                       int access)
> > > > > > +{
> > > > > > +       struct verbs_mr *vmr;
> > > > > > +       int ret;
> > > > > > +
> > > > > > +       vmr =3D 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 all=
ocates
> > > > the vmr using calloc().
> > > >
> > > > In addition, rxe_reg_mr() (not rxe_reg_dmabuf_mr()) is used the mal=
loc
> > > > and not clear the vmr. I think It has to be fixed too. Should I mak=
e
> > > > 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.ht=
ml
>
> 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.