pyverbs: Add support for implicit ODP MR

The implicit ODP MR covers the entire memory space of a process.
Applications using implicit ODP can use the entire address range
when writing to the MR, instead of being limited to the address
space registered to the MR.
This also saves actual pages registration so that application
control path is faster.

Signed-off-by: Itay Aveksis <itayav@mellanox.com>
Signed-off-by: Edward Srouji <edwards@mellanox.com>

pyverbs/mr.pyx

@@ -7,11 +7,11 @@ import logging
 from posix.mman cimport mmap, munmap, MAP_PRIVATE, PROT_READ, PROT_WRITE, \
     MAP_ANONYMOUS, MAP_HUGETLB
 from pyverbs.pyverbs_error import PyverbsError, PyverbsRDMAError
+from libc.stdint cimport uintptr_t, SIZE_MAX
 from pyverbs.base import PyverbsRDMAErrno
 from posix.stdlib cimport posix_memalign
 from libc.string cimport memcpy, memset
 cimport pyverbs.libibverbs_enums as e
-from libc.stdint cimport uintptr_t
 from pyverbs.device cimport DM
 from libc.stdlib cimport free
 from .pd cimport PD
@@ -27,16 +27,18 @@ cdef class MR(PyverbsCM):
     MR class represents ibv_mr. Buffer allocation in done in the c'tor. Freeing
     it is done in close().
     """
-    def __init__(self, PD pd not None, length=0, access=0, address=None, **kwargs):
+    def __init__(self, PD pd not None, length=0, access=0, address=None,
+                 implicit=False, **kwargs):
         """
         Allocate a user-level buffer of length <length> and register a Memory
         Region of the given length and access flags.
         :param pd: A PD object
-        :param length: Length in bytes
+        :param length: Length (in bytes) of MR's buffer.
         :param access: Access flags, see ibv_access_flags enum
         :param address: Memory address to register (Optional). If it's not
                         provided, a memory will be allocated in the class
                         initialization.
+        :param implicit: Implicit the MR address.
         :param kwargs: Arguments:
             * *handle*
                 A valid kernel handle for a MR object in the given PD.
@@ -48,10 +50,6 @@ cdef class MR(PyverbsCM):
         if self.mr != NULL:
             return
         self.is_huge = True if access & e.IBV_ACCESS_HUGETLB else False
-        # We want to enable registering an MR of size 0 but this fails with a
-        # buffer of size 0, so in this case lets increase the buffer
-        if length == 0:
-            length = 10
         if address:
             self.is_user_addr = True
             # uintptr_t is guaranteed to be large enough to hold any pointer.
@@ -70,7 +68,7 @@ cdef class MR(PyverbsCM):
             return
 
         # Allocate a buffer
-        if not address:
+        if not address and length > 0:
             if self.is_huge:
                 # Rounding up to multiple of HUGE_PAGE_SIZE
                 self.mmap_length = length + (HUGE_PAGE_SIZE - length % HUGE_PAGE_SIZE) \
@@ -86,7 +84,10 @@ cdef class MR(PyverbsCM):
                     raise PyverbsError('Failed to allocate MR buffer of size {l}'.
                                        format(l=length))
             memset(self.buf, 0, length)
-        self.mr = v.ibv_reg_mr(<v.ibv_pd*>pd.pd, self.buf, length, access)
+        if implicit:
+            self.mr = v.ibv_reg_mr(<v.ibv_pd*>pd.pd, NULL, SIZE_MAX, access)
+        else:
+            self.mr = v.ibv_reg_mr(<v.ibv_pd*>pd.pd, self.buf, length, access)
         if self.mr == NULL:
             raise PyverbsRDMAErrno('Failed to register a MR. length: {l}, access flags: {a}'.
                                    format(l=length, a=access))