8297697: RISC-V: Add support for SATP mode detection

8301067: RISC-V: better error message when reporting unsupported satp modes

Reviewed-by: fjiang, fyang
Backport-of: f49acd52594be3ec1e9682bda3ad69970dfd750d

Author: zifeihan

src/hotspot/cpu/riscv/vm_version_riscv.cpp

@@ -33,6 +33,7 @@
 #include OS_HEADER_INLINE(os)
 
 const char* VM_Version::_uarch = "";
+const char* VM_Version::_vm_mode = "";
 uint32_t VM_Version::_initial_vector_length = 0;
 
 void VM_Version::initialize() {
@@ -44,6 +45,13 @@ void VM_Version::initialize() {
 
   get_os_cpu_info();
 
+  // check if satp.mode is supported, currently supports up to SV48(RV64)
+  if (get_satp_mode() > VM_SV48) {
+    vm_exit_during_initialization(
+      err_msg("Unsupported satp mode: %s. Only satp modes up to sv48 are supported for now.",
+              _vm_mode));
+  }
+
   if (FLAG_IS_DEFAULT(UseFMA)) {
     FLAG_SET_DEFAULT(UseFMA, true);
   }

src/hotspot/cpu/riscv/vm_version_riscv.hpp

@@ -38,11 +38,22 @@ class VM_Version : public Abstract_VM_Version {
   static void c2_initialize();
 #endif // COMPILER2
 
+// VM modes (satp.mode) privileged ISA 1.10
+enum VM_MODE {
+  VM_MBARE = 0,
+  VM_SV39  = 8,
+  VM_SV48  = 9,
+  VM_SV57  = 10,
+  VM_SV64  = 11
+};
+
 protected:
   static const char* _uarch;
+  static const char* _vm_mode;
   static uint32_t _initial_vector_length;
   static void get_os_cpu_info();
   static uint32_t get_current_vector_length();
+  static VM_MODE get_satp_mode();
 
 public:
   // Initialization

src/hotspot/os_cpu/linux_riscv/vm_version_linux_riscv.cpp

@@ -75,6 +75,20 @@ uint32_t VM_Version::get_current_vector_length() {
   return (uint32_t)read_csr(CSR_VLENB);
 }
 
+VM_Version::VM_MODE VM_Version::get_satp_mode() {
+  if (!strcmp(_vm_mode, "sv39")) {
+    return VM_SV39;
+  } else if (!strcmp(_vm_mode, "sv48")) {
+    return VM_SV48;
+  } else if (!strcmp(_vm_mode, "sv57")) {
+    return VM_SV57;
+  } else if (!strcmp(_vm_mode, "sv64")) {
+    return VM_SV64;
+  } else {
+    return VM_MBARE;
+  }
+}
+
 void VM_Version::get_os_cpu_info() {
 
   uint64_t auxv = getauxval(AT_HWCAP);
@@ -103,7 +117,14 @@ void VM_Version::get_os_cpu_info() {
     char buf[512], *p;
     while (fgets(buf, sizeof (buf), f) != NULL) {
       if ((p = strchr(buf, ':')) != NULL) {
-        if (strncmp(buf, "uarch", sizeof "uarch" - 1) == 0) {
+        if (strncmp(buf, "mmu", sizeof "mmu" - 1) == 0) {
+          if (_vm_mode[0] != '\0') {
+            continue;
+          }
+          char* vm_mode = os::strdup(p + 2);
+          vm_mode[strcspn(vm_mode, "\n")] = '\0';
+          _vm_mode = vm_mode;
+        } else if (strncmp(buf, "uarch", sizeof "uarch" - 1) == 0) {
           char* uarch = os::strdup(p + 2);
           uarch[strcspn(uarch, "\n")] = '\0';
           _uarch = uarch;