From bc9b9480fbbde8ee6ad2fc118e9f0afc96dd65ec Mon Sep 17 00:00:00 2001 From: lizzie Date: Fri, 15 May 2026 22:01:42 +0200 Subject: [PATCH] [dynarmic] fix 12th-gen Intel CPUs crashing due to UMONITOR (#3954) 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 Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3954 Reviewed-by: crueter Reviewed-by: MaranBr --- src/dynarmic/src/dynarmic/common/spin_lock_x64.cpp | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/src/dynarmic/src/dynarmic/common/spin_lock_x64.cpp b/src/dynarmic/src/dynarmic/common/spin_lock_x64.cpp index e3f1721132..1a80ae638a 100644 --- a/src/dynarmic/src/dynarmic/common/spin_lock_x64.cpp +++ b/src/dynarmic/src/dynarmic/common/spin_lock_x64.cpp @@ -26,6 +26,7 @@ void EmitSpinLockLock(Xbyak::CodeGenerator& code, Xbyak::Reg64 ptr, Xbyak::Reg32 Xbyak::Label start, loop; code.jmp(start, code.T_NEAR); code.L(loop); + if (waitpkg) { // TODO: this is because we lack regalloc - so better to be safe :( code.push(Xbyak::util::rax); @@ -33,7 +34,14 @@ void EmitSpinLockLock(Xbyak::CodeGenerator& code, Xbyak::Reg64 ptr, Xbyak::Reg32 code.push(Xbyak::util::rdx); // TODO: This clobbers EAX and EDX did we tell the regalloc? // 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] = 1: C0.2 | Fast Wakup | Lesser Savings // edx:eax is implicitly used as a 64-bit deadline timestamp