IB/core: Implement support for MMU notifiers regarding on demand paging regions

* Add an interval tree implementation for ODP umems. Create an
  interval tree for each ucontext (including a count of the number of
  ODP MRs in this context, semaphore, etc.), and register ODP umems in
  the interval tree.
* Add MMU notifiers handling functions, using the interval tree to
  notify only the relevant umems and underlying MRs.
* Register to receive MMU notifier events from the MM subsystem upon
  ODP MR registration (and unregister accordingly).
* Add a completion object to synchronize the destruction of ODP umems.
* Add mechanism to abort page faults when there's a concurrent invalidation.

The way we synchronize between concurrent invalidations and page
faults is by keeping a counter of currently running invalidations, and
a sequence number that is incremented whenever an invalidation is
caught. The page fault code checks the counter and also verifies that
the sequence number hasn't progressed before it updates the umem's
page tables. This is similar to what the kvm module does.

In order to prevent the case where we register a umem in the middle of
an ongoing notifier, we also keep a per ucontext counter of the total
number of active mmu notifiers. We only enable new umems when all the
running notifiers complete.

Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Shachar Raindel <raindel@mellanox.com>
Signed-off-by: Haggai Eran <haggaie@mellanox.com>
Signed-off-by: Yuval Dagan <yuvalda@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/drivers/infiniband/core/uverbs_cmd.c b/drivers/infiniband/core/uverbs_cmd.c
index 70b697d8fbb3..532d8eba8b02 100644
--- a/drivers/infiniband/core/uverbs_cmd.c
+++ b/drivers/infiniband/core/uverbs_cmd.c
@@ -289,6 +289,9 @@ ssize_t ib_uverbs_get_context(struct ib_uverbs_file *file,
         struct ib_uverbs_get_context_resp resp;
         struct ib_udata                   udata;
         struct ib_device                 *ibdev = file->device->ib_dev;
+#ifdef CONFIG_INFINIBAND_ON_DEMAND_PAGING
+        struct ib_device_attr             dev_attr;
+#endif
         struct ib_ucontext               *ucontext;
         struct file                      *filp;
         int ret;
@@ -331,6 +334,20 @@ ssize_t ib_uverbs_get_context(struct ib_uverbs_file *file,
         rcu_read_unlock();
         ucontext->closing = 0;
 
+#ifdef CONFIG_INFINIBAND_ON_DEMAND_PAGING
+        ucontext->umem_tree = RB_ROOT;
+        init_rwsem(&ucontext->umem_rwsem);
+        ucontext->odp_mrs_count = 0;
+        INIT_LIST_HEAD(&ucontext->no_private_counters);
+
+        ret = ib_query_device(ibdev, &dev_attr);
+        if (ret)
+                goto err_free;
+        if (!(dev_attr.device_cap_flags & IB_DEVICE_ON_DEMAND_PAGING))
+                ucontext->invalidate_range = NULL;
+
+#endif
+
         resp.num_comp_vectors = file->device->num_comp_vectors;
 
         ret = get_unused_fd_flags(O_CLOEXEC);