mem: provide thread-unsafe memseg walk variant

Sometimes, user code needs to walk memseg list while being inside
a memory-related callback. Rather than making everyone copy around
the same iteration code and depending on DPDK internals, provide an
official way to do memseg_walk() inside callbacks.

Also, remove existing reimplementation from sPAPR VFIO code and use
the new API instead.

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>

diff --git a/lib/librte_eal/common/eal_common_memory.c b/lib/librte_eal/common/eal_common_memory.c
index b69c829..da45f31 100644 (file)
--- a/lib/librte_eal/common/eal_common_memory.c
+++ b/lib/librte_eal/common/eal_common_memory.c
@@ -471,14 +471,11 @@ rte_memseg_contig_walk(rte_memseg_contig_walk_t func, void *arg)
 }
 
 int __rte_experimental
-rte_memseg_walk(rte_memseg_walk_t func, void *arg)
+rte_memseg_walk_thread_unsafe(rte_memseg_walk_t func, void *arg)
 {
        struct rte_mem_config *mcfg = rte_eal_get_configuration()->mem_config;
        int i, ms_idx, ret = 0;
 
-       /* do not allow allocations/frees/init while we iterate */
-       rte_rwlock_read_lock(&mcfg->memory_hotplug_lock);
-
        for (i = 0; i < RTE_MAX_MEMSEG_LISTS; i++) {
                struct rte_memseg_list *msl = &mcfg->memsegs[i];
                const struct rte_memseg *ms;
@@ -493,18 +490,25 @@ rte_memseg_walk(rte_memseg_walk_t func, void *arg)
                while (ms_idx >= 0) {
                        ms = rte_fbarray_get(arr, ms_idx);
                        ret = func(msl, ms, arg);
-                       if (ret < 0) {
-                               ret = -1;
-                               goto out;
-                       } else if (ret > 0) {
-                               ret = 1;
-                               goto out;
-                       }
+                       if (ret)
+                               return ret;
                        ms_idx = rte_fbarray_find_next_used(arr, ms_idx + 1);
                }
        }
-out:
+       return 0;
+}
+
+int __rte_experimental
+rte_memseg_walk(rte_memseg_walk_t func, void *arg)
+{
+       struct rte_mem_config *mcfg = rte_eal_get_configuration()->mem_config;
+       int ret = 0;
+
+       /* do not allow allocations/frees/init while we iterate */
+       rte_rwlock_read_lock(&mcfg->memory_hotplug_lock);
+       ret = rte_memseg_walk_thread_unsafe(func, arg);
        rte_rwlock_read_unlock(&mcfg->memory_hotplug_lock);
+
        return ret;
 }
 

diff --git a/lib/librte_eal/common/include/rte_memory.h b/lib/librte_eal/common/include/rte_memory.h
index aeba38b..c5a84c3 100644 (file)
--- a/lib/librte_eal/common/include/rte_memory.h
+++ b/lib/librte_eal/common/include/rte_memory.h
@@ -263,6 +263,24 @@ rte_memseg_contig_walk(rte_memseg_contig_walk_t func, void *arg);
 int __rte_experimental
 rte_memseg_list_walk(rte_memseg_list_walk_t func, void *arg);
 
+/**
+ * Walk list of all memsegs without performing any locking.
+ *
+ * @note This function does not perform any locking, and is only safe to call
+ *       from within memory-related callback functions.
+ *
+ * @param func
+ *   Iterator function
+ * @param arg
+ *   Argument passed to iterator
+ * @return
+ *   0 if walked over the entire list
+ *   1 if stopped by the user
+ *   -1 if user function reported error
+ */
+int __rte_experimental
+rte_memseg_walk_thread_unsafe(rte_memseg_walk_t func, void *arg);
+
 /**
  * Walk each VA-contiguous area without performing any locking.
  *

diff --git a/lib/librte_eal/linuxapp/eal/eal_vfio.c b/lib/librte_eal/linuxapp/eal/eal_vfio.c
index a2bbdfb..14c9332 100644 (file)
--- a/lib/librte_eal/linuxapp/eal/eal_vfio.c
+++ b/lib/librte_eal/linuxapp/eal/eal_vfio.c
@@ -87,42 +87,6 @@ static const struct vfio_iommu_type iommu_types[] = {
        },
 };
 
-/* for sPAPR IOMMU, we will need to walk memseg list, but we cannot use
- * rte_memseg_walk() because by the time we enter callback we will be holding a
- * write lock, so regular rte-memseg_walk will deadlock. copying the same
- * iteration code everywhere is not ideal as well. so, use a lockless copy of
- * memseg walk here.
- */
-static int
-memseg_walk_thread_unsafe(rte_memseg_walk_t func, void *arg)
-{
-       struct rte_mem_config *mcfg = rte_eal_get_configuration()->mem_config;
-       int i, ms_idx, ret = 0;
-
-       for (i = 0; i < RTE_MAX_MEMSEG_LISTS; i++) {
-               struct rte_memseg_list *msl = &mcfg->memsegs[i];
-               const struct rte_memseg *ms;
-               struct rte_fbarray *arr;
-
-               if (msl->memseg_arr.count == 0)
-                       continue;
-
-               arr = &msl->memseg_arr;
-
-               ms_idx = rte_fbarray_find_next_used(arr, 0);
-               while (ms_idx >= 0) {
-                       ms = rte_fbarray_get(arr, ms_idx);
-                       ret = func(msl, ms, arg);
-                       if (ret < 0)
-                               return -1;
-                       if (ret > 0)
-                               return 1;
-                       ms_idx = rte_fbarray_find_next_used(arr, ms_idx + 1);
-               }
-       }
-       return 0;
-}
-
 static int
 is_null_map(const struct user_mem_map *map)
 {
@@ -1357,7 +1321,8 @@ vfio_spapr_dma_mem_map(int vfio_container_fd, uint64_t vaddr, uint64_t iova,
        /* check if window size needs to be adjusted */
        memset(&param, 0, sizeof(param));
 
-       if (memseg_walk_thread_unsafe(vfio_spapr_window_size_walk,
+       /* we're inside a callback so use thread-unsafe version */
+       if (rte_memseg_walk_thread_unsafe(vfio_spapr_window_size_walk,
                                &param) < 0) {
                RTE_LOG(ERR, EAL, "Could not get window size\n");
                ret = -1;
@@ -1386,7 +1351,9 @@ vfio_spapr_dma_mem_map(int vfio_container_fd, uint64_t vaddr, uint64_t iova,
                                ret = -1;
                                goto out;
                        }
-                       if (memseg_walk_thread_unsafe(vfio_spapr_map_walk,
+                       /* we're inside a callback, so use thread-unsafe version
+                        */
+                       if (rte_memseg_walk_thread_unsafe(vfio_spapr_map_walk,
                                        &vfio_container_fd) < 0) {
                                RTE_LOG(ERR, EAL, "Could not recreate DMA maps\n");
                                ret = -1;

diff --git a/lib/librte_eal/rte_eal_version.map b/lib/librte_eal/rte_eal_version.map
index f01661f..c5d1513 100644 (file)
--- a/lib/librte_eal/rte_eal_version.map
+++ b/lib/librte_eal/rte_eal_version.map
@@ -295,6 +295,7 @@ EXPERIMENTAL {
        rte_memseg_contig_walk_thread_unsafe;
        rte_memseg_list_walk;
        rte_memseg_walk;
+       rte_memseg_walk_thread_unsafe;
        rte_mp_action_register;
        rte_mp_action_unregister;
        rte_mp_reply;