diff --git a/gcc/config/gcn/gcn-hsa.h b/gcc/config/gcn/gcn-hsa.h
index 4611bc55392..03220555075 100644
--- a/gcc/config/gcn/gcn-hsa.h
+++ b/gcc/config/gcn/gcn-hsa.h
@@ -80,7 +80,7 @@ extern unsigned int gcn_local_sym_hash (const char *name);
    writes a new AMD GPU object file and the ABI version needs to be the
    same. - LLVM <= 17 defaults to 4 while LLVM >= 18 defaults to 5.
    GCC supports LLVM >= 13.0.1 and only LLVM >= 14 supports version 5.
-   Note that Fiji is only suppored with LLVM <= 17 as version 3 is no longer
+   Note that Fiji is only supported with LLVM <= 17 as version 3 is no longer
    supported in LLVM >= 18.  */
 #define ABI_VERSION_SPEC "march=fiji:--amdhsa-code-object-version=3;" \
 			 "!march=*|march=*:--amdhsa-code-object-version=4"
diff --git a/include/hsa.h b/include/hsa.h
index f9b5d9daf85..3c7be95d7fd 100644
--- a/include/hsa.h
+++ b/include/hsa.h
@@ -466,7 +466,9 @@ typedef enum {
   /**
   * String containing the ROCr build identifier.
   */
-  HSA_AMD_SYSTEM_INFO_BUILD_VERSION = 0x200
+  HSA_AMD_SYSTEM_INFO_BUILD_VERSION = 0x200,
+
+  HSA_AMD_SYSTEM_INFO_SVM_ACCESSIBLE_BY_DEFAULT = 0x202
 } hsa_system_info_t;
 
 /**
diff --git a/libgomp/libgomp.texi b/libgomp/libgomp.texi
index 22868635230..e79bd7a3392 100644
--- a/libgomp/libgomp.texi
+++ b/libgomp/libgomp.texi
@@ -6360,8 +6360,13 @@ The implementation remark:
       such that the next reverse offload region is only executed after the previous
       one returned.
 @item OpenMP code that has a @code{requires} directive with
-      @code{unified_shared_memory} will remove any GCN device from the list of
-      available devices (``host fallback'').
+      @code{unified_shared_memory} is only supported if all AMD GPUs have the
+      @code{HSA_AMD_SYSTEM_INFO_SVM_ACCESSIBLE_BY_DEFAULT} property; for
+      discrete GPUs, this may require setting the @code{HSA_XNACK} environment
+      variable to @samp{1}; for systems with both an APU and a discrete GPU that
+      does not support XNACK, consider using @code{ROCR_VISIBLE_DEVICES} to
+      enable only the APU.  If not supported, all AMD GPU devices are removed
+      from the list of available devices (``host fallback'').
 @item The available stack size can be changed using the @code{GCN_STACK_SIZE}
       environment variable; the default is 32 kiB per thread.
 @item Low-latency memory (@code{omp_low_lat_mem_space}) is supported when the
diff --git a/libgomp/plugin/plugin-gcn.c b/libgomp/plugin/plugin-gcn.c
index 3cdc7ba929f..3d882b5ab63 100644
--- a/libgomp/plugin/plugin-gcn.c
+++ b/libgomp/plugin/plugin-gcn.c
@@ -3355,8 +3355,25 @@ GOMP_OFFLOAD_get_num_devices (unsigned int omp_requires_mask)
   if (hsa_context.agent_count > 0
       && ((omp_requires_mask
 	   & ~(GOMP_REQUIRES_UNIFIED_ADDRESS
+	       | GOMP_REQUIRES_UNIFIED_SHARED_MEMORY
 	       | GOMP_REQUIRES_REVERSE_OFFLOAD)) != 0))
     return -1;
+  /* Check whether host page access is supported; this is per system level
+     (all GPUs supported by HSA).  While intrinsically true for APUs, it
+     requires XNACK support for discrete GPUs.  */
+  if (hsa_context.agent_count > 0
+      && (omp_requires_mask & GOMP_REQUIRES_UNIFIED_SHARED_MEMORY))
+    {
+      bool b;
+      hsa_system_info_t type = HSA_AMD_SYSTEM_INFO_SVM_ACCESSIBLE_BY_DEFAULT;
+      hsa_status_t status = hsa_fns.hsa_system_get_info_fn (type, &b);
+      if (status != HSA_STATUS_SUCCESS)
+	GOMP_PLUGIN_error ("HSA_AMD_SYSTEM_INFO_SVM_ACCESSIBLE_BY_DEFAULT "
+			   "failed");
+      if (!b)
+	return -1;
+    }
+
   return hsa_context.agent_count;
 }