8373781: [CRaC] Permit -XX:CPUFeatures on other platforms

Radim Vansa · Radim Vansa · commit abf086802d18 · 2026-01-06T14:16:39.000Z
Reviewed-by: tpushkin
diff --git a/src/hotspot/cpu/aarch64/vm_version_aarch64.cpp b/src/hotspot/cpu/aarch64/vm_version_aarch64.cpp
@@ -636,6 +636,8 @@ void VM_Version::initialize() {
     _features &= ~CPU_SVE;
   }
 
+  check_cpufeatures_vmoptions();
+
   // Construct the "features" string
   char buf[512];
   int buf_used_len = os::snprintf_checked(buf, sizeof(buf), "0x%02x:0x%x:0x%03x:%d", _cpu, _variant, _model, _revision);
diff --git a/src/hotspot/cpu/aarch64/vm_version_aarch64.hpp b/src/hotspot/cpu/aarch64/vm_version_aarch64.hpp
@@ -66,7 +66,7 @@ class VM_Version : public Abstract_VM_Version {
   static void initialize();
   struct VM_Features: public Zero_Features {};
   static bool cpu_features_binary(VM_Features *data) { return false; }
-  static bool ignore_cpu_features(bool is_checkpoint) { return true; }
+  static bool ignore_cpu_features() { return true; }
   static void check_virtualizations();
 
   static void print_platform_virtualization_info(outputStream*);
diff --git a/src/hotspot/cpu/arm/vm_version_arm.hpp b/src/hotspot/cpu/arm/vm_version_arm.hpp
@@ -43,7 +43,7 @@ class VM_Version: public Abstract_VM_Version {
   static bool is_initialized()      { return _is_initialized; }
   struct VM_Features: public Zero_Features {};
   static bool cpu_features_binary(VM_Features *data) { return false; }
-  static bool ignore_cpu_features(bool is_checkpoint) { return true; }
+  static bool ignore_cpu_features() { return true; }
 
 
  protected:
diff --git a/src/hotspot/cpu/arm/vm_version_arm_32.cpp b/src/hotspot/cpu/arm/vm_version_arm_32.cpp
@@ -350,6 +350,8 @@ void VM_Version::initialize() {
     FLAG_SET_DEFAULT(UseUnalignedAccesses, false);
   }
 
+  check_cpufeatures_vmoptions();
+
   _is_initialized = true;
 }
 
diff --git a/src/hotspot/cpu/ppc/vm_version_ppc.cpp b/src/hotspot/cpu/ppc/vm_version_ppc.cpp
@@ -331,6 +331,8 @@ void VM_Version::initialize() {
   }
 
   check_virtualizations();
+
+  check_cpufeatures_vmoptions();
 }
 
 void VM_Version::check_virtualizations() {
diff --git a/src/hotspot/cpu/ppc/vm_version_ppc.hpp b/src/hotspot/cpu/ppc/vm_version_ppc.hpp
@@ -55,7 +55,7 @@ class VM_Version: public Abstract_VM_Version {
   static void check_virtualizations();
   struct VM_Features: public Zero_Features {};
   static bool cpu_features_binary(VM_Features *data) { return false; }
-  static bool ignore_cpu_features(bool is_checkpoint) { return true; }
+  static bool ignore_cpu_features() { return true; }
 
   // Override Abstract_VM_Version implementation
   static void print_platform_virtualization_info(outputStream*);
diff --git a/src/hotspot/cpu/riscv/vm_version_riscv.cpp b/src/hotspot/cpu/riscv/vm_version_riscv.cpp
@@ -62,6 +62,8 @@ void VM_Version::initialize() {
 #ifdef COMPILER2
   c2_initialize();
 #endif // COMPILER2
+
+  check_cpufeatures_vmoptions();
 }
 
 void VM_Version::common_initialize() {
diff --git a/src/hotspot/cpu/riscv/vm_version_riscv.hpp b/src/hotspot/cpu/riscv/vm_version_riscv.hpp
@@ -309,7 +309,7 @@ class VM_Version : public Abstract_VM_Version {
   static void initialize_cpu_information();
   struct VM_Features: public Zero_Features {};
   static bool cpu_features_binary(VM_Features *data) { return false; }
-  static bool ignore_cpu_features(bool is_checkpoint) { return true; }
+  static bool ignore_cpu_features() { return true; }
 
   constexpr static bool supports_stack_watermark_barrier() { return true; }
 
diff --git a/src/hotspot/cpu/s390/vm_version_s390.cpp b/src/hotspot/cpu/s390/vm_version_s390.cpp
@@ -328,6 +328,8 @@ void VM_Version::initialize() {
   if (FLAG_IS_DEFAULT(UseUnalignedAccesses)) {
     FLAG_SET_DEFAULT(UseUnalignedAccesses, true);
   }
+
+  check_cpufeatures_vmoptions();
 }
 
 
diff --git a/src/hotspot/cpu/s390/vm_version_s390.hpp b/src/hotspot/cpu/s390/vm_version_s390.hpp
@@ -416,7 +416,7 @@ class VM_Version: public Abstract_VM_Version {
   static bool is_determine_features_test_running() { return _is_determine_features_test_running; }
   struct VM_Features: public Zero_Features {};
   static bool cpu_features_binary(VM_Features *data) { return false; }
-  static bool ignore_cpu_features(bool is_checkpoint) { return true; }
+  static bool ignore_cpu_features() { return true; }
 
   // Override Abstract_VM_Version implementation
   static void print_platform_virtualization_info(outputStream*);
diff --git a/src/hotspot/cpu/x86/globals_x86.hpp b/src/hotspot/cpu/x86/globals_x86.hpp
@@ -182,20 +182,6 @@ define_pd_global(intx, InitArrayShortSize, 8*BytesPerLong);
              "Turn off JVM mitigations related to Intel micro code "        \
              "mitigations for the Intel JCC erratum")                       \
                                                                             \
-  product(ccstr, CPUFeatures, nullptr, "CPU feature set, "                  \
-          "use -XX:CPUFeatures=0xnumber with -XX:CRaCCheckpointTo when you "\
-          "get an error during -XX:CRaCRestoreFrom on a different machine; "\
-          "-XX:CPUFeatures=native is the default; "                         \
-          "-XX:CPUFeatures=ignore will disable the CPU features check; "    \
-          "-XX:CPUFeatures=generic is compatible but not as slow as 0")     \
-                                                                            \
-  product(bool, ShowCPUFeatures, false, "Show features of this CPU "        \
-          "to be possibly used for the -XX:CPUFeatures=0xnumber option")    \
-                                                                            \
-  product(bool, IgnoreCPUFeatures, false, RESTORE_SETTABLE | EXPERIMENTAL,  \
-          "Do not refuse to run after -XX:CRaCRestoreFrom finds out some "  \
-          "CPU features are missing")                                       \
-                                                                            \
   product(int, X86ICacheSync, -1, DIAGNOSTIC,                               \
              "Select the X86 ICache sync mechanism: -1 = auto-select; "     \
              "0 = none (dangerous); 1 = CLFLUSH loop; 2 = CLFLUSHOPT loop; "\
diff --git a/src/hotspot/cpu/x86/vm_version_x86.cpp b/src/hotspot/cpu/x86/vm_version_x86.cpp
@@ -891,8 +891,7 @@ class VM_Version_StubGenerator: public StubCodeGenerator {
 VM_Version::VM_Features VM_Version::CPUFeatures_parse(const char *str) {
 #ifndef LINUX
   _ignore_glibc_not_using = true;
-  return _features;
-#else
+#endif // !LINUX
   if (str == nullptr || strcmp(str, "native") == 0) {
     return _features;
   }
@@ -901,6 +900,9 @@ VM_Version::VM_Features VM_Version::CPUFeatures_parse(const char *str) {
     return _features;
   }
   if (strcmp(str, "generic") == 0) {
+#ifndef LINUX
+    return _features;
+#else
     // 32-bit x86 cannot rely on anything.
     VM_Version::VM_Features retval;
 #ifdef AMD64
@@ -917,7 +919,12 @@ VM_Version::VM_Features VM_Version::CPUFeatures_parse(const char *str) {
     // CPU_LAHFSAHF is disabled in 'gcc -Q --help=target' and "Early Intel Pentium 4 CPUs with Intel 64 support ... lacked the LAHF and SAHF instructions"
 #endif
     return retval;
+#endif // !LINUX
   }
+#ifndef LINUX
+  vm_exit_during_initialization("This OS does not support any arch-specific -XX:CPUFeatures options");
+  return {};
+#else // LINUX
   int count = VM_Version::VM_Features::features_bitmap_element_count();
   VM_Version::VM_Features retval;
   const char *str_orig = str;
@@ -946,7 +953,7 @@ VM_Version::VM_Features VM_Version::CPUFeatures_parse(const char *str) {
   }
   vm_exit_during_initialization(err_msg("VM option 'CPUFeatures=%s' must be of the form: %s", str_orig, buf + 1));
   return {};
-#endif // LINUX
+#endif
 }
 
 bool VM_Version::_ignore_glibc_not_using = false;
diff --git a/src/hotspot/cpu/x86/vm_version_x86.hpp b/src/hotspot/cpu/x86/vm_version_x86.hpp
@@ -937,11 +937,11 @@ class VM_Version : public Abstract_VM_Version {
   // Initialization
   static void initialize();
   static bool cpu_features_binary(VM_Features *data);
-  static bool ignore_cpu_features(bool is_checkpoint) {
+  static bool ignore_cpu_features() {
     // This gets triggered by -XX:CPUFeatures=ignore, not writing the features & arch
     // on checkpoint into the image at all, and skipping the check on restore.
     // IgnoreCPUFeatures is ignored on checkpoint
-    return _ignore_glibc_not_using || (!is_checkpoint && IgnoreCPUFeatures);
+    return _ignore_glibc_not_using;
   }
   static void restore_check(const char* str, const char* msg_prefix);
 
diff --git a/src/hotspot/cpu/zero/vm_version_zero.cpp b/src/hotspot/cpu/zero/vm_version_zero.cpp
@@ -139,6 +139,8 @@ void VM_Version::initialize() {
   // the support unconditionally.
   _supports_cx8 = true;
 #endif
+
+  check_cpufeatures_vmoptions();
 }
 
 void VM_Version::initialize_cpu_information(void) {
diff --git a/src/hotspot/cpu/zero/vm_version_zero.hpp b/src/hotspot/cpu/zero/vm_version_zero.hpp
@@ -34,7 +34,7 @@ class VM_Version : public Abstract_VM_Version {
   static void initialize();
   struct VM_Features: public Zero_Features {};
   static bool cpu_features_binary(VM_Features *data) { return false; }
-  static bool ignore_cpu_features(bool is_checkpoint) { return true; }
+  static bool ignore_cpu_features() { return true; }
 
   constexpr static bool supports_stack_watermark_barrier() { return true; }
 
diff --git a/src/hotspot/share/runtime/abstract_vm_version.cpp b/src/hotspot/share/runtime/abstract_vm_version.cpp
@@ -26,6 +26,7 @@
 #include "compiler/compilerDefinitions.hpp"
 #include "jvm_io.h"
 #include "runtime/arguments.hpp"
+#include "runtime/globals_extension.hpp"
 #include "runtime/vm_version.hpp"
 #include "utilities/globalDefinitions.hpp"
 
@@ -402,3 +403,14 @@ const char* Abstract_VM_Version::cpu_description(void) {
   strncpy(tmp, _cpu_desc, CPU_DETAILED_DESC_BUF_SIZE);
   return tmp;
 }
+
+void Abstract_VM_Version::check_cpufeatures_vmoptions() {
+  if (!FLAG_IS_DEFAULT(CPUFeatures)) {
+    if (strcmp(CPUFeatures, "native") && strcmp(CPUFeatures, "generic") && strcmp(CPUFeatures, "ignore")) {
+      vm_exit_during_initialization("This architecture does not support any arch-specific -XX:CPUFeatures options");
+    }
+  }
+  if (!FLAG_IS_DEFAULT(ShowCPUFeatures)) {
+    tty->print_cr("Do not use -XX:ShowCPUFeatures: this architecture does not support any arch-specific strings.");
+  }
+}
diff --git a/src/hotspot/share/runtime/abstract_vm_version.hpp b/src/hotspot/share/runtime/abstract_vm_version.hpp
@@ -227,6 +227,9 @@ class Abstract_VM_Version: AllStatic {
   static char  _cpu_name[CPU_TYPE_DESC_BUF_SIZE];
   static char  _cpu_desc[CPU_DETAILED_DESC_BUF_SIZE];
 
+  // Default check for non-x86_64 architectures on VM options sanity
+  static void check_cpufeatures_vmoptions();
+
  public:
   static int number_of_threads(void);
   static int number_of_cores(void);
diff --git a/src/hotspot/share/runtime/crac.cpp b/src/hotspot/share/runtime/crac.cpp
@@ -317,7 +317,7 @@ int crac::checkpoint_restore(int *shmid) {
 
   // Setup CPU arch & features only during the first checkpoint; the feature set
   // cannot change after initial boot (and we don't support switching the engine).
-  if (_generation == 1 && !VM_Version::ignore_cpu_features(true)) {
+  if (_generation == 1 && !VM_Version::ignore_cpu_features()) {
     VM_Version::VM_Features data;
     if (VM_Version::cpu_features_binary(&data)) {
       switch (_engine->prepare_image_constraints_api()) {
@@ -812,7 +812,7 @@ void crac::restore(crac_restore_data& restore_data) {
   // was printed out but continued even despite features not being satisfied.
   // Since the check itself is delegated to the C/R Engine we will simply
   // skip the check here.
-  if (!VM_Version::ignore_cpu_features(false)) {
+  if (!VM_Version::ignore_cpu_features() && !IgnoreCPUFeatures) {
     switch (engine.prepare_image_constraints_api()) {
       case CracEngine::ApiStatus::OK: {
         VM_Version::VM_Features data;
diff --git a/src/hotspot/share/runtime/globals.hpp b/src/hotspot/share/runtime/globals.hpp
@@ -2029,6 +2029,22 @@ const int ObjectAlignmentInBytes = 8;
   product(size_t, CRaCMaxHeapSizeBeforeCheckpoint, 0, "Maximum size "       \
           "of heap before checkpoint. By default equals to -Xmx.")          \
                                                                             \
+  product(ccstr, CPUFeatures, nullptr, "CPU feature set, "                  \
+          "Limit set of CPU features to make the CRaC image compatible "    \
+          "for running on a machine with different CPU:"                    \
+          "native: use all available features (default), "                  \
+          "generic: compatible with most CPUs, "                            \
+          "ignore: do not store CPU features at all, "                      \
+          "<arch-specific>: use -XX:+ShowCPUFeatures to find a suitable "   \
+          "architecture-specific string, e.g. 0xnumber,0xnumber on x86_64.")\
+                                                                            \
+  product(bool, ShowCPUFeatures, false, "Show features of this CPU "        \
+          "to be possibly used for the -XX:CPUFeatures=0xnumber option")    \
+                                                                            \
+  product(bool, IgnoreCPUFeatures, false, RESTORE_SETTABLE | EXPERIMENTAL,  \
+          "Do not refuse to run after -XX:CRaCRestoreFrom finds out some "  \
+          "CPU features are missing")                                       \
+                                                                            \
   product(int, LockingMode, LM_LIGHTWEIGHT,                                 \
           "(Deprecated) Select locking mode: "                              \
           "0: (Deprecated) monitors only (LM_MONITOR), "                    \
diff --git a/src/java.base/share/man/java.md b/src/java.base/share/man/java.md
@@ -1881,11 +1881,24 @@ performed by the Java HotSpot VM.
     compilation while values greater than 1.0 delay compilation. Setting
     `CompileThresholdScaling` to 0 is equivalent to disabling compilation.
 
-`-XX:CPUFeatures=`*0xnumber,0xnumber*
-:   CPU feature set, use `-XX:CPUFeatures=`*0xnumber,0xnumber* with
-    `-XX:CRaCCheckpointTo` when you get an error during `-XX:CRaCRestoreFrom`
-    on a different machine. `-XX:CPUFeatures=native` is the default.
-    `-XX:CPUFeatures=generic` is compatible with any CPU.
+`-XX:CPUFeatures=`*features*
+:   Limit the set of CPU features to make the CRaC image compatible for running
+    on a machine with a different CPU:
+
+    `native`
+    :   Use all available CPU features (default).
+
+    `generic`
+    :   This option is compatible with most CPUs and faster than disabling
+        all optional features.
+
+    `ignore`
+    :   Do not store CPU features at all.
+
+    *arch-specific*
+    :   Architecture specific string, e.g. *0xnumber,0xnumber* on x86_64.
+        Use `-XX:+ShowCPUFeatures` to find a suitable architecture-specific
+        string.
 
 `-XX:+DoEscapeAnalysis`
 :   Enables the use of escape analysis. This option is enabled by default. To
diff --git a/test/jdk/jdk/crac/CPUFeatures/SimpleCPUFeatures.sh b/test/jdk/jdk/crac/CPUFeatures/SimpleCPUFeatures.sh
diff --git a/test/jdk/jdk/crac/CPUFeatures/SimpleCPUFeaturesTest.java b/test/jdk/jdk/crac/CPUFeatures/SimpleCPUFeaturesTest.java

Original file line number	Diff line number	Diff line change
`@@ -636,6 +636,8 @@ void VM_Version::initialize() {`
`636`	`636`	`_features &= ~CPU_SVE;`
`637`	`637`	`}`
`638`	`638`
	`639`	`+ check_cpufeatures_vmoptions();`
	`640`	`+`
`639`	`641`	`// Construct the "features" string`
`640`	`642`	`char buf[512];`
`641`	`643`	`int buf_used_len = os::snprintf_checked(buf, sizeof(buf), "0x%02x:0x%x:0x%03x:%d", _cpu, _variant, _model, _revision);`
Original file line number	Diff line number	Diff line change
`@@ -350,6 +350,8 @@ void VM_Version::initialize() {`
`350`	`350`	`FLAG_SET_DEFAULT(UseUnalignedAccesses, false);`
`351`	`351`	`}`
`352`	`352`
	`353`	`+ check_cpufeatures_vmoptions();`
	`354`	`+`
`353`	`355`	`_is_initialized = true;`
`354`	`356`	`}`
`355`	`357`
Original file line number	Diff line number	Diff line change
`@@ -331,6 +331,8 @@ void VM_Version::initialize() {`
`331`	`331`	`}`
`332`	`332`
`333`	`333`	`check_virtualizations();`
	`334`	`+`
	`335`	`+ check_cpufeatures_vmoptions();`
`334`	`336`	`}`
`335`	`337`
`336`	`338`	`void VM_Version::check_virtualizations() {`
Original file line number	Diff line number	Diff line change
`@@ -62,6 +62,8 @@ void VM_Version::initialize() {`
`62`	`62`	`#ifdef COMPILER2`
`63`	`63`	`c2_initialize();`
`64`	`64`	`#endif // COMPILER2`
	`65`	`+`
	`66`	`+ check_cpufeatures_vmoptions();`
`65`	`67`	`}`
`66`	`68`
`67`	`69`	`void VM_Version::common_initialize() {`
Original file line number	Diff line number	Diff line change
`@@ -328,6 +328,8 @@ void VM_Version::initialize() {`
`328`	`328`	`if (FLAG_IS_DEFAULT(UseUnalignedAccesses)) {`
`329`	`329`	`FLAG_SET_DEFAULT(UseUnalignedAccesses, true);`
`330`	`330`	`}`
	`331`	`+`
	`332`	`+ check_cpufeatures_vmoptions();`
`331`	`333`	`}`
`332`	`334`
`333`	`335`