From: Thomas Huth <1748296@bugs.launchpad.net>
To: qemu-devel@nongnu.org
Subject: [Bug 1748296] Re: TCG throws Invalid Opcode when executing x86 BMI shlx instruction
Date: Thu, 22 Apr 2021 05:34:44 -0000 [thread overview]
Message-ID: <161906968444.32072.9259428871119294115.malone@soybean.canonical.com> (raw)
In-Reply-To: 151812332204.10331.17425660234309724521.malonedeb@wampee.canonical.com
Ah, never mind, posted the text before seeing that it still affects
people in 2021 ... so I'm not changing this bug to "Incomplete". Sorry
for the noise.
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https://bugs.launchpad.net/bugs/1748296
Title:
TCG throws Invalid Opcode when executing x86 BMI shlx instruction
Status in QEMU:
New
Bug description:
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 QEMU 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.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1748296/+subscriptions
next prev parent reply other threads:[~2021-04-22 5:44 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-08 20:55 [Qemu-devel] [Bug 1748296] [NEW] TCG throws Invalid Opcode when executing x86 BMI shlx instruction Doug Gale
2018-02-08 21:50 ` [Qemu-devel] [Bug 1748296] " Doug Gale
2021-01-14 4:26 ` David Greenaway
2021-04-22 5:33 ` Thomas Huth
2021-04-22 5:34 ` Thomas Huth [this message]
2021-04-30 8:56 ` Thomas Huth
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