Merge pull request open-mpi#7304 from hjelmn/btl_vader_fix_max_address_on_aarch64

btl/vader: modify how the max attachment address is determined

Author: hjelmn

opal/mca/btl/vader/btl_vader.h

@@ -17,6 +17,7 @@
  * Copyright (c) 2015      Mellanox Technologies. All rights reserved.
  * Copyright (c) 2018      Triad National Security, LLC. All rights
  *                         reserved.
+ * Copyright (c) 2020      Google, LLC. All rights reserved.
  *
  * $COPYRIGHT$
  *
@@ -82,6 +83,7 @@ union vader_modex_t {
     struct vader_modex_xpmem_t {
         xpmem_segid_t seg_id;
         void *segment_base;
+        uintptr_t address_max;
     } xpmem;
 #endif
     struct vader_modex_other_t {
@@ -113,6 +115,7 @@ struct mca_btl_vader_component_t {
     int vader_free_list_inc;                /**< number of elements to alloc when growing free lists */
 #if OPAL_BTL_VADER_HAVE_XPMEM
     xpmem_segid_t my_seg_id;                /**< this rank's xpmem segment id */
+    uintptr_t my_address_max;               /**< largest address */
     mca_rcache_base_vma_module_t *vma_module; /**< registration cache for xpmem segments */
 #endif
     opal_shmem_ds_t seg_ds;                 /**< this rank's shared memory segment (when not using xpmem) */

opal/mca/btl/vader/btl_vader_component.c

@@ -21,7 +21,7 @@
  * Copyright (c) 2018      Amazon.com, Inc. or its affiliates.  All Rights reserved.
  * Copyright (c) 2018      Triad National Security, LLC. All rights
  *                         reserved.
- * Copyright (c) 2019      Google, Inc. All rights reserved.
+ * Copyright (c) 2019-2020 Google, Inc. All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -383,6 +383,7 @@ static int mca_btl_base_vader_modex_send (void)
     if (MCA_BTL_VADER_XPMEM == mca_btl_vader_component.single_copy_mechanism) {
         modex.xpmem.seg_id = mca_btl_vader_component.my_seg_id;
         modex.xpmem.segment_base = mca_btl_vader_component.my_segment;
+        modex.xpmem.address_max = mca_btl_vader_component.my_address_max;
 
         modex_size = sizeof (modex.xpmem);
     } else {

opal/mca/btl/vader/btl_vader_endpoint.h

@@ -78,6 +78,7 @@ typedef struct mca_btl_base_endpoint_t {
 #if OPAL_BTL_VADER_HAVE_XPMEM
         struct {
             xpmem_apid_t    apid;       /**< xpmem apid for remote peer */
+            uintptr_t       address_max; /**< largest address that can be attached */
         } xpmem;
 #endif
         struct {

opal/mca/btl/vader/btl_vader_module.c

@@ -19,6 +19,7 @@
  *                         and Technology (RIST).  All rights reserved.
  * Copyright (c) 2018-2019 Triad National Security, LLC. All rights
  *                         reserved.
+ * Copyright (c) 2020      Google, LLC. All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -216,6 +217,7 @@ static int init_vader_endpoint (struct mca_btl_base_endpoint_t *ep, struct opal_
         if (MCA_BTL_VADER_XPMEM == mca_btl_vader_component.single_copy_mechanism) {
             /* always use xpmem if it is available */
             ep->segment_data.xpmem.apid = xpmem_get (modex->xpmem.seg_id, XPMEM_RDWR, XPMEM_PERMIT_MODE, (void *) 0666);
+            ep->segment_data.xpmem.address_max = modex->xpmem.address_max;
             (void) vader_get_registation (ep, modex->xpmem.segment_base, mca_btl_vader_component.segment_size,
                                           MCA_RCACHE_FLAGS_PERSIST, (void **) &ep->segment_base);
         } else {

opal/mca/btl/vader/btl_vader_xpmem.c

@@ -22,7 +22,47 @@
 
 int mca_btl_vader_xpmem_init (void)
 {
-    mca_btl_vader_component.my_seg_id = xpmem_make (0, VADER_MAX_ADDRESS, XPMEM_PERMIT_MODE, (void *)0666);
+    /* Any attachment that goes past the Linux TASK_SIZE will always fail. To prevent this we need to
+     * determine the value of TASK_SIZE. On x86_64 the value was hard-coded in vader to be
+     * 0x7ffffffffffful but this approach does not work with AARCH64 (and possibly other architectures).
+     * Since there is really no way to directly determine the value we can (in all cases?) look through
+     * the mapping for this process to determine what the largest address is. This should be the top
+     * of the stack. No heap allocations should be larger than this value. Since the largest address
+     * may differ between processes the value must be shared as part of the modex and stored in the
+     * endpoint. */
+    FILE *fh = fopen("/proc/self/maps", "r");
+    if (NULL == fh) {
+        BTL_ERROR(("could not open /proc/self/maps for reading. disabling XPMEM"));
+        return OPAL_ERR_NOT_AVAILABLE;
+    }
+
+    char buffer[1024];
+    uintptr_t address_max = 0;
+    while (fgets(buffer, sizeof(buffer), fh)) {
+        uintptr_t low, high;
+        char *tmp;
+        /* each line of /proc/self/maps starts with low-high in hexidecimal (without a 0x) */
+        low = strtoul(buffer, &tmp, 16);
+        high = strtoul(tmp+1, NULL, 16);
+        if (address_max < high) {
+            address_max = high;
+        }
+    }
+
+    fclose (fh);
+
+    if (0 == address_max) {
+        BTL_ERROR(("could not determine the address max"));
+        return OPAL_ERR_NOT_AVAILABLE;
+    }
+
+    /* save the calcuated maximum */
+    mca_btl_vader_component.my_address_max = address_max - 1;
+
+    /* it is safe to use XPMEM_MAXADDR_SIZE here (which is always (size_t)-1 even though
+     * it is not safe for attach */
+    mca_btl_vader_component.my_seg_id = xpmem_make (0, XPMEM_MAXADDR_SIZE, XPMEM_PERMIT_MODE,
+                                                    (void *)0666);
     if (-1 == mca_btl_vader_component.my_seg_id) {
         return OPAL_ERR_NOT_AVAILABLE;
     }
@@ -110,8 +150,8 @@ mca_rcache_base_registration_t *vader_get_registation (struct mca_btl_base_endpo
 
     base = OPAL_DOWN_ALIGN((uintptr_t) rem_ptr, attach_align, uintptr_t);
     bound = OPAL_ALIGN((uintptr_t) rem_ptr + size - 1, attach_align, uintptr_t) + 1;
-    if (OPAL_UNLIKELY(bound > VADER_MAX_ADDRESS)) {
-        bound = VADER_MAX_ADDRESS;
+    if (OPAL_UNLIKELY(bound > ep->segment_data.xpmem.address_max)) {
+        bound = ep->segment_data.xpmem.address_max;
     }
 
     check_ctx.base = base;

opal/mca/btl/vader/btl_vader_xpmem.h

@@ -3,6 +3,7 @@
  * Copyright (c) 2013-2014 Los Alamos National Security, LLC. All rights
  *                         reserved.
  * Copyright (c) 2016      ARM, Inc. All rights reserved.
+ * Copyright (c) 2020      Google, LLC. All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -32,13 +33,6 @@
 /* look up the remote pointer in the peer rcache and attach if
  * necessary */
 
-/* largest address we can attach to using xpmem */
-#if defined(__x86_64__)
-#define VADER_MAX_ADDRESS ((uintptr_t)0x7ffffffff000ul)
-#else
-#define VADER_MAX_ADDRESS XPMEM_MAXADDR_SIZE
-#endif
-
 struct mca_btl_base_endpoint_t;
 
 int mca_btl_vader_xpmem_init (void);