net/sunrpc/xprtrdma/physical_ops.c

   1 /*
   2  * Copyright (c) 2015 Oracle.  All rights reserved.
   3  * Copyright (c) 2003-2007 Network Appliance, Inc. All rights reserved.
   4  */
   5
   6 /* No-op chunk preparation. All client memory is pre-registered.
   7  * Sometimes referred to as ALLPHYSICAL mode.
   8  *
   9  * Physical registration is simple because all client memory is
  10  * pre-registered and never deregistered. This mode is good for
  11  * adapter bring up, but is considered not safe: the server is
  12  * trusted not to abuse its access to client memory not involved
  13  * in RDMA I/O.
  14  */
  15
  16 #include "xprt_rdma.h"
  17
  18 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
  19 # define RPCDBG_FACILITY        RPCDBG_TRANS
  20 #endif
  21
  22 static int
  23 physical_op_open(struct rpcrdma_ia *ia, struct rpcrdma_ep *ep,
  24                  struct rpcrdma_create_data_internal *cdata)
  25 {
  26         struct ib_mr *mr;
  27
  28         /* Obtain an rkey to use for RPC data payloads.
  29          */
  30         mr = ib_get_dma_mr(ia->ri_pd,
  31                            IB_ACCESS_LOCAL_WRITE |
  32                            IB_ACCESS_REMOTE_WRITE |
  33                            IB_ACCESS_REMOTE_READ);
  34         if (IS_ERR(mr)) {
  35                 pr_err("%s: ib_get_dma_mr for failed with %lX\n",
  36                        __func__, PTR_ERR(mr));
  37                 return -ENOMEM;
  38         }
  39         ia->ri_dma_mr = mr;
  40
  41         rpcrdma_set_max_header_sizes(ia, cdata, min_t(unsigned int,
  42                                                       RPCRDMA_MAX_DATA_SEGS,
  43                                                       RPCRDMA_MAX_HDR_SEGS));
  44         return 0;
  45 }
  46
  47 /* PHYSICAL memory registration conveys one page per chunk segment.
  48  */
  49 static size_t
  50 physical_op_maxpages(struct rpcrdma_xprt *r_xprt)
  51 {
  52         return min_t(unsigned int, RPCRDMA_MAX_DATA_SEGS,
  53                      RPCRDMA_MAX_HDR_SEGS);
  54 }
  55
  56 static int
  57 physical_op_init(struct rpcrdma_xprt *r_xprt)
  58 {
  59         return 0;
  60 }
  61
  62 /* The client's physical memory is already exposed for
  63  * remote access via RDMA READ or RDMA WRITE.
  64  */
  65 static int
  66 physical_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
  67                 int nsegs, bool writing)
  68 {
  69         struct rpcrdma_ia *ia = &r_xprt->rx_ia;
  70
  71         rpcrdma_map_one(ia->ri_device, seg, rpcrdma_data_dir(writing));
  72         seg->mr_rkey = ia->ri_dma_mr->rkey;
  73         seg->mr_base = seg->mr_dma;
  74         return 1;
  75 }
  76
  77 /* DMA unmap all memory regions that were mapped for "req".
  78  */
  79 static void
  80 physical_op_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
  81 {
  82         struct ib_device *device = r_xprt->rx_ia.ri_device;
  83         unsigned int i;
  84
  85         for (i = 0; req->rl_nchunks; --req->rl_nchunks)
  86                 rpcrdma_unmap_one(device, &req->rl_segments[i++]);
  87 }
  88
  89 /* Use a slow, safe mechanism to invalidate all memory regions
  90  * that were registered for "req".
  91  *
  92  * For physical memory registration, there is no good way to
  93  * fence a single MR that has been advertised to the server. The
  94  * client has already handed the server an R_key that cannot be
  95  * invalidated and is shared by all MRs on this connection.
  96  * Tearing down the PD might be the only safe choice, but it's
  97  * not clear that a freshly acquired DMA R_key would be different
  98  * than the one used by the PD that was just destroyed.
  99  * FIXME.
 100  */
 101 static void
 102 physical_op_unmap_safe(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
 103                        bool sync)
 104 {
 105         physical_op_unmap_sync(r_xprt, req);
 106 }
 107
 108 static void
 109 physical_op_destroy(struct rpcrdma_buffer *buf)
 110 {
 111 }
 112
 113 const struct rpcrdma_memreg_ops rpcrdma_physical_memreg_ops = {
 114         .ro_map                         = physical_op_map,
 115         .ro_unmap_sync                  = physical_op_unmap_sync,
 116         .ro_unmap_safe                  = physical_op_unmap_safe,
 117         .ro_open                        = physical_op_open,
 118         .ro_maxpages                    = physical_op_maxpages,
 119         .ro_init                        = physical_op_init,
 120         .ro_destroy                     = physical_op_destroy,
 121         .ro_displayname                 = "physical",
 122 };