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8360776: Disable Intel APX by default and enable it with -XX:+UnlockExperimentalVMOptions -XX:+UseAPX in all builds #26029

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8360776: Disable Intel APX by default and enable it with -XX:+UnlockExperimentalVMOptions -XX:+UseAPX in all builds #26029

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10 changes: 0 additions & 10 deletions src/hotspot/cpu/x86/vm_version_x86.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -440,7 +440,6 @@ class VM_Version_StubGenerator: public StubCodeGenerator {
__ andl(rax, Address(rbp, in_bytes(VM_Version::xem_xcr0_offset()))); // xcr0 bits apx_f
__ jcc(Assembler::equal, vector_save_restore);

#ifndef PRODUCT
bool save_apx = UseAPX;
VM_Version::set_apx_cpuFeatures();
UseAPX = true;
Expand All @@ -457,7 +456,6 @@ class VM_Version_StubGenerator: public StubCodeGenerator {
__ movq(Address(rsi, 8), r31);

UseAPX = save_apx;
#endif
__ bind(vector_save_restore);
//
// Check if OS has enabled XGETBV instruction to access XCR0
Expand Down Expand Up @@ -1022,8 +1020,6 @@ void VM_Version::get_processor_features() {
if (UseAPX && !apx_supported) {
warning("UseAPX is not supported on this CPU, setting it to false");
FLAG_SET_DEFAULT(UseAPX, false);
} else if (FLAG_IS_DEFAULT(UseAPX)) {
FLAG_SET_DEFAULT(UseAPX, apx_supported ? true : false);
}

if (!UseAPX) {
Expand Down Expand Up @@ -3151,17 +3147,11 @@ bool VM_Version::os_supports_apx_egprs() {
if (!supports_apx_f()) {
return false;
}
// Enable APX support for product builds after
// completion of planned features listed in JDK-8329030.
Comment on lines -3154 to -3155
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@dholmes-ora dholmes-ora Jun 30, 2025 •
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So you have decided not to follow the original plan ( as JDK-8329030 is not complete) and instead go ahead and enable APX in product mode now. Why? Was this discussed anywhere?

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@dholmes-ora The remaining items in JDK-8329030 are nice to have. I will update JDK-8329030 accordingly to reflect this.

#if !defined(PRODUCT)
if (_cpuid_info.apx_save[0] != egpr_test_value() ||
_cpuid_info.apx_save[1] != egpr_test_value()) {
return false;
}
return true;
#else
return false;
#endif
}

uint VM_Version::cores_per_cpu() {
Expand Down
2 changes: 0 additions & 2 deletions src/hotspot/os/windows/os_windows.cpp
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Expand Up @@ -2623,15 +2623,13 @@ LONG WINAPI topLevelExceptionFilter(struct _EXCEPTION_POINTERS* exceptionInfo) {
return Handle_Exception(exceptionInfo, VM_Version::cpuinfo_cont_addr());
}

#if !defined(PRODUCT)
if ((exception_code == EXCEPTION_ACCESS_VIOLATION) &&
VM_Version::is_cpuinfo_segv_addr_apx(pc)) {
// Verify that OS save/restore APX registers.
VM_Version::clear_apx_test_state();
return Handle_Exception(exceptionInfo, VM_Version::cpuinfo_cont_addr_apx());
}
#endif
#endif

#ifdef CAN_SHOW_REGISTERS_ON_ASSERT
if (VMError::was_assert_poison_crash(exception_record)) {
Expand Down
2 changes: 0 additions & 2 deletions src/hotspot/os_cpu/bsd_x86/os_bsd_x86.cpp
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Expand Up @@ -429,13 +429,11 @@ bool PosixSignals::pd_hotspot_signal_handler(int sig, siginfo_t* info,
stub = VM_Version::cpuinfo_cont_addr();
}

#if !defined(PRODUCT) && defined(_LP64)
if ((sig == SIGSEGV || sig == SIGBUS) && VM_Version::is_cpuinfo_segv_addr_apx(pc)) {
// Verify that OS save/restore APX registers.
stub = VM_Version::cpuinfo_cont_addr_apx();
VM_Version::clear_apx_test_state();
}
#endif

// We test if stub is already set (by the stack overflow code
// above) so it is not overwritten by the code that follows. This
Expand Down
2 changes: 0 additions & 2 deletions src/hotspot/os_cpu/linux_x86/os_linux_x86.cpp
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Expand Up @@ -255,13 +255,11 @@ bool PosixSignals::pd_hotspot_signal_handler(int sig, siginfo_t* info,
stub = VM_Version::cpuinfo_cont_addr();
}

#if !defined(PRODUCT) && defined(_LP64)
if ((sig == SIGSEGV) && VM_Version::is_cpuinfo_segv_addr_apx(pc)) {
// Verify that OS save/restore APX registers.
stub = VM_Version::cpuinfo_cont_addr_apx();
VM_Version::clear_apx_test_state();
}
#endif

if (thread->thread_state() == _thread_in_Java) {
// Java thread running in Java code => find exception handler if any
Expand Down