Re: [PATCH v2 1/2] migration/rdma: Try to register On-Demand Paging memory region

[Marcel Apfelbaum]

Hi Zhijian,

On Mon, Aug 23, 2021 at 11:42 AM lizhijian@fujitsu.com
<lizhijian@fujitsu.com> wrote:
>
> CCing  Marcel
>
>
> On 23/08/2021 11:33, Li Zhijian wrote:
> > Previously, for the fsdax mem-backend-file, it will register failed with
> > Operation not supported. In this case, we can try to register it with
> > On-Demand Paging[1] like what rpma_mr_reg() does on rpma[2].
> >
> > [1]: 
> > https://community.mellanox.com/s/article/understanding-on-demand-paging--odp-x
> > [2]: http://pmem.io/rpma/manpages/v0.9.0/rpma_mr_reg.3
> >
> > CC: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
> > Signed-off-by: Li Zhijian <lizhijian@cn.fujitsu.com>
> >
> > ---
> > V2: add ODP sanity check and remove goto
> > ---
> >   migration/rdma.c       | 73 ++++++++++++++++++++++++++++++------------
> >   migration/trace-events |  1 +
> >   2 files changed, 54 insertions(+), 20 deletions(-)
> >
> > diff --git a/migration/rdma.c b/migration/rdma.c
> > index 5c2d113aa94..eb80431aae2 100644
> > --- a/migration/rdma.c
> > +++ b/migration/rdma.c
> > @@ -1117,19 +1117,47 @@ static int qemu_rdma_alloc_qp(RDMAContext *rdma)
> >       return 0;
> >   }
> >
> > +/* Check whether On-Demand Paging is supported by RDAM device */
> > +static bool rdma_support_odp(struct ibv_context *dev)
> > +{
> > +    struct ibv_device_attr_ex attr = {0};
> > +    int ret = ibv_query_device_ex(dev, NULL, &attr);
> > +    if (ret) {
> > +        return false;
> > +    }
> > +
> > +    if (attr.odp_caps.general_caps & IBV_ODP_SUPPORT) {
> > +        return true;
> > +    }
> > +
> > +    return false;
> > +}
> > +
> >   static int qemu_rdma_reg_whole_ram_blocks(RDMAContext *rdma)
> >   {
> >       int i;
> >       RDMALocalBlocks *local = &rdma->local_ram_blocks;
> >
> >       for (i = 0; i < local->nb_blocks; i++) {
> > +        int access = IBV_ACCESS_LOCAL_WRITE | IBV_ACCESS_REMOTE_WRITE;
> > +
> >           local->block[i].mr =
> >               ibv_reg_mr(rdma->pd,
> >                       local->block[i].local_host_addr,
> > -                    local->block[i].length,
> > -                    IBV_ACCESS_LOCAL_WRITE |
> > -                    IBV_ACCESS_REMOTE_WRITE
> > +                    local->block[i].length, access
> >                       );
> > +
> > +        if (!local->block[i].mr &&
> > +            errno == ENOTSUP && rdma_support_odp(rdma->verbs)) {
> > +                access |= IBV_ACCESS_ON_DEMAND;
> > +                /* register ODP mr */
> > +                local->block[i].mr =
> > +                    ibv_reg_mr(rdma->pd,
> > +                               local->block[i].local_host_addr,
> > +                               local->block[i].length, access);
> > +                
> > trace_qemu_rdma_register_odp_mr(local->block[i].block_name);
> > +        }
> > +
> >           if (!local->block[i].mr) {
> >               perror("Failed to register local dest ram block!");
> >               break;
> > @@ -1215,28 +1243,33 @@ static int 
> > qemu_rdma_register_and_get_keys(RDMAContext *rdma,
> >        */
> >       if (!block->pmr[chunk]) {
> >           uint64_t len = chunk_end - chunk_start;
> > +        int access = rkey ? IBV_ACCESS_LOCAL_WRITE | 
> > IBV_ACCESS_REMOTE_WRITE :
> > +                     0;
> >
> >           trace_qemu_rdma_register_and_get_keys(len, chunk_start);
> >
> > -        block->pmr[chunk] = ibv_reg_mr(rdma->pd,
> > -                chunk_start, len,
> > -                (rkey ? (IBV_ACCESS_LOCAL_WRITE |
> > -                        IBV_ACCESS_REMOTE_WRITE) : 0));
> > -
> > -        if (!block->pmr[chunk]) {
> > -            perror("Failed to register chunk!");
> > -            fprintf(stderr, "Chunk details: block: %d chunk index %d"
> > -                            " start %" PRIuPTR " end %" PRIuPTR
> > -                            " host %" PRIuPTR
> > -                            " local %" PRIuPTR " registrations: %d\n",
> > -                            block->index, chunk, (uintptr_t)chunk_start,
> > -                            (uintptr_t)chunk_end, host_addr,
> > -                            (uintptr_t)block->local_host_addr,
> > -                            rdma->total_registrations);
> > -            return -1;
> > +        block->pmr[chunk] = ibv_reg_mr(rdma->pd, chunk_start, len, access);
> > +        if (!block->pmr[chunk] &&
> > +            errno == ENOTSUP && rdma_support_odp(rdma->verbs)) {
> > +            access |= IBV_ACCESS_ON_DEMAND;
> > +            /* register ODP mr */
> > +            block->pmr[chunk] = ibv_reg_mr(rdma->pd, chunk_start, len, 
> > access);
> > +            trace_qemu_rdma_register_odp_mr(block->block_name);
> >           }
> > -        rdma->total_registrations++;
> >       }
> > +    if (!block->pmr[chunk]) {
> > +        perror("Failed to register chunk!");
> > +        fprintf(stderr, "Chunk details: block: %d chunk index %d"
> > +                        " start %" PRIuPTR " end %" PRIuPTR
> > +                        " host %" PRIuPTR
> > +                        " local %" PRIuPTR " registrations: %d\n",
> > +                        block->index, chunk, (uintptr_t)chunk_start,
> > +                        (uintptr_t)chunk_end, host_addr,
> > +                        (uintptr_t)block->local_host_addr,
> > +                        rdma->total_registrations);
> > +        return -1;
> > +    }
> > +    rdma->total_registrations++;
> >
> >       if (lkey) {
> >           *lkey = block->pmr[chunk]->lkey;
> > diff --git a/migration/trace-events b/migration/trace-events
> > index a1c0f034ab8..5f6aa580def 100644
> > --- a/migration/trace-events
> > +++ b/migration/trace-events
> > @@ -212,6 +212,7 @@ qemu_rdma_poll_write(const char *compstr, int64_t comp, 
> > int left, uint64_t block
> >   qemu_rdma_poll_other(const char *compstr, int64_t comp, int left) "other 
> > completion %s (%" PRId64 ") received left %d"
> >   qemu_rdma_post_send_control(const char *desc) "CONTROL: sending %s.."
> >   qemu_rdma_register_and_get_keys(uint64_t len, void *start) "Registering 
> > %" PRIu64 " bytes @ %p"
> > +qemu_rdma_register_odp_mr(const char *name) "Try to register On-Demand 
> > Paging memory region: %s"
> >   qemu_rdma_registration_handle_compress(int64_t length, int index, int64_t 
> > offset) "Zapping zero chunk: %" PRId64 " bytes, index %d, offset %" PRId64
> >   qemu_rdma_registration_handle_finished(void) ""
> >   qemu_rdma_registration_handle_ram_blocks(void) ""

Reviewed-by: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>

Thanks,
Marcel