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Diffstat (limited to 'results/classifier/gemma3:27b/instruction/1748296')
| -rw-r--r-- | results/classifier/gemma3:27b/instruction/1748296 | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/results/classifier/gemma3:27b/instruction/1748296 b/results/classifier/gemma3:27b/instruction/1748296 new file mode 100644 index 00000000..73411abc --- /dev/null +++ b/results/classifier/gemma3:27b/instruction/1748296 @@ -0,0 +1,28 @@ + + + +TCG throws Invalid Opcode when executing x86 BMI shlx instruction + +I am unable to use BMI in my project when running under TCG. I narrowed the problem down to incorrect instruction decoding for BMI instructions (which have a 2 byte VEX prefix). The gen_sse function in translate.c reaches the goto label do_0f_38_fx, but b does not equal 0x1f7, 0x2f7, or 0x3f7, so the switch takes the default path and raises an invalid opcode exception. + +The code executes correctly and passes the test under KVM. + +I have created a complete repro here: https://github.com/doug65536/qemu-bmibug + +The makefile has the following utility targets: + +debug-kvm: Build and run the VM using KVM and wait for gdbstub attach + +run: Run the test case with TCG, make fails if the test fails. (It will fail) + +run-kvm: Run the test case with KVM, make fails if the test fails. (It will succeed) + +debug: Build and run the VM with TCG and wait for GDB attach + +attach-gdb: Run GDB and attach to KVM gdbstub + +The VM runs with -cpu max. CPUID reports support for BMI, BMI2, and ABM. + +You can quickly verify the issue by executing `make run-kvm` to confirm that KVM passes, then `make run` to confirm that TCG fails. + +I believe the bug affects other BMI, BMI2, and ABM instructions, but I have only completely verified incorrect execution of SHLX. \ No newline at end of file |