id = 842
title = "ppc64: hard lockup / hang in Linux kernel v5.17-rc1"
state = "closed"
created_at = "2022-01-26T18:55:49.662Z"
closed_at = "2022-01-27T14:44:52.204Z"
labels = ["kind::Bug", "target: ppc", "workflow::Triaged"]
url = "https://gitlab.com/qemu-project/qemu/-/issues/842"
host-os = "Ubuntu 20.04.3 LTS"
host-arch = "x86_64"
qemu-version = "master as of 48302d4eb628 (as well as 6.0.0 and Ubuntu's 4.2.1)"
guest-os = "Linux kernel only"
guest-arch = "ppc64le"
description = """The kernel deterministically triggers a hard lockup / hang under QEMU since v5.17-rc1 (upgrading from v5.16).

Bisecting points to the kernel's [0faf20a1ad16](https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0faf20a1ad1647c0fc0f5a367c71e5e84deaf899) ("powerpc/64s/interrupt: Don't enable MSR[EE] in irq handlers unless perf is in use"). Reverting it on top of v5.17-rc1 fixes the issue.

Reported to [linuxppc-dev](https://lore.kernel.org/linuxppc-dev/CANiq72n_FmDx=r-o9J8gYc6LpwRL5EGmhM6Xzwv27Xc7h1TNDw@mail.gmail.com/). Confirmed. Suspected QEMU modeling issue by Cédric Le Goater."""
reproduce = """1. Build kernel v5.17-rc1 or commit 0faf20a1ad16 for ppc64le with the attached config (either GCC or Clang).
2. Run it under QEMU with at least `-smp 2`."""
additional = """[qemu-and-dmesg.log](/uploads/7cb5ce1cb70e06262800c16f4c800157/qemu-and-dmesg.log)
[kernel.config](/uploads/327e9cec48a731abc9e44cb40db67de9/kernel.config)"""