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

[Zhu Yanjun]

On Thu, Sep 30, 2021 at 7:06 PM Shunsuke Mie <mie@xxxxxxxxxx> wrote:
>
> 2021年9月30日(木) 16:23 Zhu Yanjun <zyjzyj2000@xxxxxxxxx>:
> >
> > On Thu, Sep 30, 2021 at 2:58 PM Shunsuke Mie <mie@xxxxxxxxxx> wrote:
> > >
> > > 2021年9月30日(木) 15:37 Zhu Yanjun <zyjzyj2000@xxxxxxxxx>:
> > > >
> > > > On Thu, Sep 30, 2021 at 2:20 PM Shunsuke Mie <mie@xxxxxxxxxx> wrote:
> > > > >
> > > > > Implement a new provider method for dma-buf base memory registration.
> > > > >
> > > > > Signed-off-by: Shunsuke Mie <mie@xxxxxxxxxx>
> > > > > ---
> > > > >  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