id = 997
title = "Iothread is stuck at 100% CPU usage with virtio-scsi on QEMU 7.0.0"
state = "closed"
created_at = "2022-04-21T21:21:52.081Z"
closed_at = "2022-04-27T17:34:22.896Z"
labels = ["Storage", "device:virtio"]
url = "https://gitlab.com/qemu-project/qemu/-/issues/997"
host-os = "Gentoo Unstable"
host-arch = "amd64"
qemu-version = "7.0.0"
guest-os = "Fedora 35 ISO (kernel 5.14.10), Windows 10 21H1"
guest-arch = "amd64"
description = """Starting with QEMU 7.0.0, the iothread associated attached to a virtio-scsi controller is stuck at 100% CPU usage. Bisected to: https://gitlab.com/qemu-project/qemu/-/commit/826cc32423db2a99d184dbf4f507c737d7e7a4ae

- Works as expected without the iothread
- No issue with virtio-blk + iothread
- Same behavior regardless of io=threads/native/io_uring
- Same behavior with default vs increased queue count
- The issue is triggered when the guest OS initializes the virtio driver"""
reproduce = """1. Add virtio-scsi controller with iothread
2. Boot VM
3. Check per-thread CPU usage such as in htop"""
additional = """[fedora.log](/uploads/776fbf8e5b823d0ab326946684ef9022/fedora.log)

[fedora.xml](/uploads/54879e5adfb227ddef79d382e86fc608/fedora.xml)"""