id = 1696
title = "Linux kernel hangs rarely when booting on the latest qemu"
state = "closed"
created_at = "2023-06-08T14:54:10.244Z"
closed_at = "2023-06-22T14:01:51.130Z"
labels = []
url = "https://gitlab.com/qemu-project/qemu/-/issues/1696"
host-os = "Fedora 37, 38 and Rawhide"
host-arch = "x86-64"
qemu-version = "qemu-system-x86-8.0.0-4.fc39.x86_64"
guest-os = "Linux"
guest-arch = "x86_64"
description = """(Downstream bug: https://bugzilla.redhat.com/show_bug.cgi?id=2213346)

In Fedora we have noticed that the latest Linux kernel (rarely) hangs when booting
on the latest qemu.  It hangs after printing:

```
[    0.070120] x86/cpu: User Mode Instruction Prevention (UMIP) activated
[    0.070120] Last level iTLB entries: 4KB 512, 2MB 255, 4MB 127
[    0.070120] Last level dTLB entries: 4KB 512, 2MB 255, 4MB 127, 1GB 0
[    0.070120] Spectre V1 : Mitigation: usercopy/swapgs barriers and __user pointer sanitization
[    0.070120] Spectre V2 : Mitigation: Retpolines
[    0.070120] Spectre V2 : Spectre v2 / SpectreRSB mitigation: Filling RSB on context switch
[    0.070120] Spectre V2 : Spectre v2 / SpectreRSB : Filling RSB on VMEXIT
[    0.070120] Spectre V2 : Enabling Speculation Barrier for firmware calls
[    0.070120] RETBleed: Mitigation: untrained return thunk
[    0.070120] Spectre V2 : mitigation: Enabling conditional Indirect Branch Prediction Barrier
[    0.070120] Speculative Store Bypass: Mitigation: Speculative Store Bypass disabled via prctl
[    0.070120] Freeing SMP alternatives memory: 48K
```

The next line which would be printed (if it didn't hang) is:

```
[    0.070794] smpboot: CPU0: AMD Ryzen 9 3900X 12-Core Processor (family: 0x17, model: 0x71, stepping: 0x0)
```

We've seen this hang on both AMD and Intel.  It probably happens one in every 300 boots."""
reproduce = """By far the easiest way to reproduce this is to just run guestfish in a loop:

```
$ while guestfish -a /dev/null -v run >& /tmp/log; do echo -n . ; done 
```"""
additional = """The full qemu command is rather long but you can find it in this log file:

https://bugzilla-attachments.redhat.com/attachment.cgi?id=1969620"""