Re: [RFC PATCH v2 2/2] RDMA/rxe: Add dma-buf support

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Oct 01, 2021 at 12:56:48PM +0900, Shunsuke Mie wrote:
> 2021年9月30日(木) 23:41 Daniel Vetter <daniel@ffwll.ch>:
> >
> > On Wed, Sep 29, 2021 at 01:19:05PM +0900, Shunsuke Mie wrote:
> > > Implement a ib device operation ‘reg_user_mr_dmabuf’. Generate a
> > > rxe_map from the memory space linked the passed dma-buf.
> > >
> > > Signed-off-by: Shunsuke Mie <mie@igel.co.jp>
> > > ---
> > >  drivers/infiniband/sw/rxe/rxe_loc.h   |   2 +
> > >  drivers/infiniband/sw/rxe/rxe_mr.c    | 118 ++++++++++++++++++++++++++
> > >  drivers/infiniband/sw/rxe/rxe_verbs.c |  34 ++++++++
> > >  drivers/infiniband/sw/rxe/rxe_verbs.h |   2 +
> > >  4 files changed, 156 insertions(+)
> > >
> > > diff --git a/drivers/infiniband/sw/rxe/rxe_loc.h b/drivers/infiniband/sw/rxe/rxe_loc.h
> > > index 1ca43b859d80..8bc19ea1a376 100644
> > > --- a/drivers/infiniband/sw/rxe/rxe_loc.h
> > > +++ b/drivers/infiniband/sw/rxe/rxe_loc.h
> > > @@ -75,6 +75,8 @@ u8 rxe_get_next_key(u32 last_key);
> > >  void rxe_mr_init_dma(struct rxe_pd *pd, int access, struct rxe_mr *mr);
> > >  int rxe_mr_init_user(struct rxe_pd *pd, u64 start, u64 length, u64 iova,
> > >                    int access, struct rxe_mr *mr);
> > > +int rxe_mr_dmabuf_init_user(struct rxe_pd *pd, int fd, u64 start, u64 length,
> > > +                         u64 iova, int access, struct rxe_mr *mr);
> > >  int rxe_mr_init_fast(struct rxe_pd *pd, int max_pages, struct rxe_mr *mr);
> > >  int rxe_mr_copy(struct rxe_mr *mr, u64 iova, void *addr, int length,
> > >               enum rxe_mr_copy_dir dir);
> > > diff --git a/drivers/infiniband/sw/rxe/rxe_mr.c b/drivers/infiniband/sw/rxe/rxe_mr.c
> > > index 53271df10e47..af6ef671c3a5 100644
> > > --- a/drivers/infiniband/sw/rxe/rxe_mr.c
> > > +++ b/drivers/infiniband/sw/rxe/rxe_mr.c
> > > @@ -4,6 +4,7 @@
> > >   * Copyright (c) 2015 System Fabric Works, Inc. All rights reserved.
> > >   */
> > >
> > > +#include <linux/dma-buf.h>
> > >  #include "rxe.h"
> > >  #include "rxe_loc.h"
> > >
> > > @@ -245,6 +246,120 @@ int rxe_mr_init_user(struct rxe_pd *pd, u64 start, u64 length, u64 iova,
> > >       return err;
> > >  }
> > >
> > > +static int rxe_map_dmabuf_mr(struct rxe_mr *mr,
> > > +                          struct ib_umem_dmabuf *umem_dmabuf)
> > > +{
> > > +     struct rxe_map_set *set;
> > > +     struct rxe_phys_buf *buf = NULL;
> > > +     struct rxe_map **map;
> > > +     void *vaddr, *vaddr_end;
> > > +     int num_buf = 0;
> > > +     int err;
> > > +     size_t remain;
> > > +
> > > +     mr->dmabuf_map = kzalloc(sizeof &mr->dmabuf_map, GFP_KERNEL);
> >
> > dmabuf_maps are just tagged pointers (and we could shrink them to actually
> > just a tagged pointer if anyone cares about the overhead of the separate
> > bool), allocating them seperately is overkill.
> 
> I agree with you. However, I think it is needed to unmap by
> dma_buf_vunmap(). If there is another simple way to unmap it. It is not
> needed I think. What do you think about it?

dma_buf_vunmap does not kfree the dma_buf_map argument, so that's no
reason to allocate it separately. Or I'm confused.

Also apologies, I'm way behind on mails.
-Daniel

> 
> > > +     if (!mr->dmabuf_map) {
> > > +             err = -ENOMEM;
> > > +             goto err_out;
> > > +     }
> > > +
> > > +     err = dma_buf_vmap(umem_dmabuf->dmabuf, mr->dmabuf_map);
> > > +     if (err)
> > > +             goto err_free_dmabuf_map;
> > > +
> > > +     set = mr->cur_map_set;
> > > +     set->page_shift = PAGE_SHIFT;
> > > +     set->page_mask = PAGE_SIZE - 1;
> > > +
> > > +     map = set->map;
> > > +     buf = map[0]->buf;
> > > +
> > > +     vaddr = mr->dmabuf_map->vaddr;
> >
> > dma_buf_map can be an __iomem too, you shouldn't dig around in this, but
> > use the dma-buf-map.h helpers instead. On x86 (and I think also on most
> > arm) it doesn't matter, but it's kinda not very nice in a pure software
> > driver.
> >
> > If anything is missing in dma-buf-map.h wrappers just add more.
> >
> > Or alternatively you need to fail the import if you can't handle __iomem.
> >
> > Aside from these I think the dma-buf side here for cpu access looks
> > reasonable now.
> > -Daniel
> I'll see the dma-buf-map.h and consider the error handling that you suggested.
> I appreciate your support.
> 
> Thanks a lot,
> Shunsuke.
> 
> > > +     vaddr_end = vaddr + umem_dmabuf->dmabuf->size;
> > > +     remain = umem_dmabuf->dmabuf->size;
> > > +
> > > +     for (; remain; vaddr += PAGE_SIZE) {
> > > +             if (num_buf >= RXE_BUF_PER_MAP) {
> > > +                     map++;
> > > +                     buf = map[0]->buf;
> > > +                     num_buf = 0;
> > > +             }
> > > +
> > > +             buf->addr = (uintptr_t)vaddr;
> > > +             if (remain >= PAGE_SIZE)
> > > +                     buf->size = PAGE_SIZE;
> > > +             else
> > > +                     buf->size = remain;
> > > +             remain -= buf->size;
> > > +
> > > +             num_buf++;
> > > +             buf++;
> > > +     }
> > > +
> > > +     return 0;
> > > +
> > > +err_free_dmabuf_map:
> > > +     kfree(mr->dmabuf_map);
> > > +err_out:
> > > +     return err;
> > > +}
> > > +
> > > +static void rxe_unmap_dmabuf_mr(struct rxe_mr *mr)
> > > +{
> > > +     struct ib_umem_dmabuf *umem_dmabuf = to_ib_umem_dmabuf(mr->umem);
> > > +
> > > +     dma_buf_vunmap(umem_dmabuf->dmabuf, mr->dmabuf_map);
> > > +     kfree(mr->dmabuf_map);
> > > +}
> > > +
> > > +int rxe_mr_dmabuf_init_user(struct rxe_pd *pd, int fd, u64 start, u64 length,
> > > +                         u64 iova, int access, struct rxe_mr *mr)
> > > +{
> > > +     struct ib_umem_dmabuf *umem_dmabuf;
> > > +     struct rxe_map_set *set;
> > > +     int err;
> > > +
> > > +     umem_dmabuf = ib_umem_dmabuf_get(pd->ibpd.device, start, length, fd,
> > > +                                      access, NULL);
> > > +     if (IS_ERR(umem_dmabuf)) {
> > > +             err = PTR_ERR(umem_dmabuf);
> > > +             goto err_out;
> > > +     }
> > > +
> > > +     rxe_mr_init(access, mr);
> > > +
> > > +     err = rxe_mr_alloc(mr, ib_umem_num_pages(&umem_dmabuf->umem), 0);
> > > +     if (err) {
> > > +             pr_warn("%s: Unable to allocate memory for map\n", __func__);
> > > +             goto err_release_umem;
> > > +     }
> > > +
> > > +     mr->ibmr.pd = &pd->ibpd;
> > > +     mr->umem = &umem_dmabuf->umem;
> > > +     mr->access = access;
> > > +     mr->state = RXE_MR_STATE_VALID;
> > > +     mr->type = IB_MR_TYPE_USER;
> > > +
> > > +     set = mr->cur_map_set;
> > > +     set->length = length;
> > > +     set->iova = iova;
> > > +     set->va = start;
> > > +     set->offset = ib_umem_offset(mr->umem);
> > > +
> > > +     err = rxe_map_dmabuf_mr(mr, umem_dmabuf);
> > > +     if (err)
> > > +             goto err_free_map_set;
> > > +
> > > +     return 0;
> > > +
> > > +err_free_map_set:
> > > +     rxe_mr_free_map_set(mr->num_map, mr->cur_map_set);
> > > +err_release_umem:
> > > +     ib_umem_release(&umem_dmabuf->umem);
> > > +err_out:
> > > +     return err;
> > > +}
> > > +
> > >  int rxe_mr_init_fast(struct rxe_pd *pd, int max_pages, struct rxe_mr *mr)
> > >  {
> > >       int err;
> > > @@ -703,6 +818,9 @@ void rxe_mr_cleanup(struct rxe_pool_entry *arg)
> > >  {
> > >       struct rxe_mr *mr = container_of(arg, typeof(*mr), pelem);
> > >
> > > +     if (mr->umem && mr->umem->is_dmabuf)
> > > +             rxe_unmap_dmabuf_mr(mr);
> > > +
> > >       ib_umem_release(mr->umem);
> > >
> > >       if (mr->cur_map_set)
> > > diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.c b/drivers/infiniband/sw/rxe/rxe_verbs.c
> > > index 9d0bb9aa7514..6191bb4f434d 100644
> > > --- a/drivers/infiniband/sw/rxe/rxe_verbs.c
> > > +++ b/drivers/infiniband/sw/rxe/rxe_verbs.c
> > > @@ -916,6 +916,39 @@ static struct ib_mr *rxe_reg_user_mr(struct ib_pd *ibpd,
> > >       return ERR_PTR(err);
> > >  }
> > >
> > > +static struct ib_mr *rxe_reg_user_mr_dmabuf(struct ib_pd *ibpd, u64 start,
> > > +                                         u64 length, u64 iova, int fd,
> > > +                                         int access, struct ib_udata *udata)
> > > +{
> > > +     int err;
> > > +     struct rxe_dev *rxe = to_rdev(ibpd->device);
> > > +     struct rxe_pd *pd = to_rpd(ibpd);
> > > +     struct rxe_mr *mr;
> > > +
> > > +     mr = rxe_alloc(&rxe->mr_pool);
> > > +     if (!mr) {
> > > +             err = -ENOMEM;
> > > +             goto err2;
> > > +     }
> > > +
> > > +     rxe_add_index(mr);
> > > +
> > > +     rxe_add_ref(pd);
> > > +
> > > +     err = rxe_mr_dmabuf_init_user(pd, fd, start, length, iova, access, mr);
> > > +     if (err)
> > > +             goto err3;
> > > +
> > > +     return &mr->ibmr;
> > > +
> > > +err3:
> > > +     rxe_drop_ref(pd);
> > > +     rxe_drop_index(mr);
> > > +     rxe_drop_ref(mr);
> > > +err2:
> > > +     return ERR_PTR(err);
> > > +}
> > > +
> > >  static struct ib_mr *rxe_alloc_mr(struct ib_pd *ibpd, enum ib_mr_type mr_type,
> > >                                 u32 max_num_sg)
> > >  {
> > > @@ -1081,6 +1114,7 @@ static const struct ib_device_ops rxe_dev_ops = {
> > >       .query_qp = rxe_query_qp,
> > >       .query_srq = rxe_query_srq,
> > >       .reg_user_mr = rxe_reg_user_mr,
> > > +     .reg_user_mr_dmabuf = rxe_reg_user_mr_dmabuf,
> > >       .req_notify_cq = rxe_req_notify_cq,
> > >       .resize_cq = rxe_resize_cq,
> > >
> > > diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.h b/drivers/infiniband/sw/rxe/rxe_verbs.h
> > > index c807639435eb..0aa95ab06b6e 100644
> > > --- a/drivers/infiniband/sw/rxe/rxe_verbs.h
> > > +++ b/drivers/infiniband/sw/rxe/rxe_verbs.h
> > > @@ -334,6 +334,8 @@ struct rxe_mr {
> > >
> > >       struct rxe_map_set      *cur_map_set;
> > >       struct rxe_map_set      *next_map_set;
> > > +
> > > +     struct dma_buf_map *dmabuf_map;
> > >  };
> > >
> > >  enum rxe_mw_state {
> > > --
> > > 2.17.1
> > >
> >
> > --
> > Daniel Vetter
> > Software Engineer, Intel Corporation
> > http://blog.ffwll.ch

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch