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[dynarmic] fix 12th-gen Intel CPUs crashing due to UMONITOR (#3954)

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see https://github.com/herumi/xbyak/issues/255

> Proof: https://godbolt.org/z/9vseq4Ynj
> Xbyak currently implements it as:
> ```c++
> void umonitor(const Reg& r) {
> int idx = r.getIdx();
> if (idx > 7) XBYAK_THROW(ERR_BAD_PARAMETER) //umonitor DOES accept r8,r9,r10,etc this is NOT correct
> int bit = r.getBit();
> if (BIT != bit) {
>   if ((BIT == 32 && bit == 16) || (BIT == 64 && bit == 32)) {
>     db(0x67);
>   } else {
>     XBYAK_THROW(ERR_BAD_SIZE_OF_REGISTER)
>   }
> }
> db(0xF3); db(0x0F); db(0xAE); setModRM(3, 6, idx);
> }
> ```
> My program was throwing Xbyak::Exception and I tracked it down to this particular umonitor

Signed-off-by: lizzie <lizzie@eden-emu.dev>
Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3954
Reviewed-by: crueter <crueter@eden-emu.dev>
Reviewed-by: MaranBr <maranbr@eden-emu.dev>
This commit is contained in:
lizzie 2026-05-15 22:01:42 +02:00 • committed by crueter
parent d1ceeeca22
commit bc9b9480fb
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1 changed files with 9 additions and 1 deletions
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10
src/dynarmic/src/dynarmic/common/spin_lock_x64.cpp
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@ -26,6 +26,7 @@ void EmitSpinLockLock(Xbyak::CodeGenerator& code, Xbyak::Reg64 ptr, Xbyak::Reg32
Xbyak::Label start, loop; Xbyak::Label start, loop;
code.jmp(start, code.T_NEAR); code.jmp(start, code.T_NEAR);
code.L(loop); code.L(loop);
if (waitpkg) { if (waitpkg) {
// TODO: this is because we lack regalloc - so better to be safe :( // TODO: this is because we lack regalloc - so better to be safe :(
code.push(Xbyak::util::rax); code.push(Xbyak::util::rax);
@ -33,7 +34,14 @@ void EmitSpinLockLock(Xbyak::CodeGenerator& code, Xbyak::Reg64 ptr, Xbyak::Reg32
code.push(Xbyak::util::rdx); code.push(Xbyak::util::rdx);
// TODO: This clobbers EAX and EDX did we tell the regalloc? // TODO: This clobbers EAX and EDX did we tell the regalloc?
// ARM ptr for address-monitoring // ARM ptr for address-monitoring
code.umonitor(ptr);
// XBYAK BUG: code.umonitor(ptr); see issue #255
// replace once xbyak has been fixed
code.db(0xF3);
if (ptr.getIdx() >= 8) code.db(0x41);
code.db(0x0F); code.db(0xAE);
code.db(uint8_t((3 << 6) | ((6 & 7) << 3) | (ptr.getIdx() & 7)));
// tmp.bit[0] = 0: C0.1 | Slow Wakup | Better Savings // tmp.bit[0] = 0: C0.1 | Slow Wakup | Better Savings
// tmp.bit[0] = 1: C0.2 | Fast Wakup | Lesser Savings // tmp.bit[0] = 1: C0.2 | Fast Wakup | Lesser Savings
// edx:eax is implicitly used as a 64-bit deadline timestamp // edx:eax is implicitly used as a 64-bit deadline timestamp