[Qemu-devel] [Bug 1815889] Re: qemu-system-x86_64 crashed with signal 31 in __pthread_setaffinity_new()

["Christian Ehrhardt " <1815889@bugs.launchpad.net>]

Summary:
- qemu crash when using GL
- "sched_setaffinity" is the syscall that is seccomp blocked and kills qemu
- the mesa i915 drivers (and your radeon as well) will do that call
- it is blocked by the current qemu -sanbox on,...,resourcecontrol=deny which is libvirts default
- Implemented by qemu 24f8cdc572
- Similar issue being fixed last year qemu 056de1e894
- new code in mesa 18.3 since mesa d877451b48

I think we just need to allow sched_setaffinity with these new mesa drivers in the wild.
The alternative to detect gl usage in libvirt and only then allow ressourcecontrol IMHO seems over-engineered (needs internals to actually pass the need of seccomp subsets to be switched) and not better (more syscalls will be non-blocked then as the -secomp interface isn't fine grained).

OTOH the man page literally says "... Disable process affinity ...", so I'm not sure we can just remove it. Maybe split resourcecontrol in two, put *affinity* in the new one and make the default being not blocked - so that upper layers like libvirt will work until one explicitly states ... -sandbox on,affinity=on which no one wanting to use GL would do. That again seems too much.
Well the discussion will happen either here on ML/bug or latter when submitting an RFC for it.

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https://bugs.launchpad.net/bugs/1815889

Title:
  qemu-system-x86_64 crashed with signal 31 in
  __pthread_setaffinity_new()

Status in QEMU:
  New
Status in qemu package in Ubuntu:
  Triaged

Bug description:
  Unable to launch Default Fedora 29 images in gnome-boxes

  ProblemType: Crash
  DistroRelease: Ubuntu 19.04
  Package: qemu-system-x86 1:3.1+dfsg-2ubuntu1
  ProcVersionSignature: Ubuntu 4.19.0-12.13-generic 4.19.18
  Uname: Linux 4.19.0-12-generic x86_64
  ApportVersion: 2.20.10-0ubuntu20
  Architecture: amd64
  Date: Thu Feb 14 11:00:45 2019
  ExecutablePath: /usr/bin/qemu-system-x86_64
  KvmCmdLine: COMMAND         STAT  EUID  RUID   PID  PPID %CPU COMMAND
  MachineType: Dell Inc. Precision T3610
  ProcEnviron: PATH=(custom, user)
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.19.0-12-generic root=UUID=939b509b-d627-4642-a655-979b44972d17 ro splash quiet vt.handoff=1
  Signal: 31
  SourcePackage: qemu
  StacktraceTop:
   __pthread_setaffinity_new (th=<optimized out>, cpusetsize=128, cpuset=0x7f5771fbf680) at ../sysdeps/unix/sysv/linux/pthread_setaffinity.c:34
   () at /usr/lib/x86_64-linux-gnu/dri/radeonsi_dri.so
   () at /usr/lib/x86_64-linux-gnu/dri/radeonsi_dri.so
   start_thread (arg=<optimized out>) at pthread_create.c:486
   clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95
  Title: qemu-system-x86_64 crashed with signal 31 in __pthread_setaffinity_new()
  UpgradeStatus: Upgraded to disco on 2018-11-14 (91 days ago)
  UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo video
  dmi.bios.date: 11/14/2018
  dmi.bios.vendor: Dell Inc.
  dmi.bios.version: A18
  dmi.board.name: 09M8Y8
  dmi.board.vendor: Dell Inc.
  dmi.board.version: A01
  dmi.chassis.type: 7
  dmi.chassis.vendor: Dell Inc.
  dmi.modalias: dmi:bvnDellInc.:bvrA18:bd11/14/2018:svnDellInc.:pnPrecisionT3610:pvr00:rvnDellInc.:rn09M8Y8:rvrA01:cvnDellInc.:ct7:cvr:
  dmi.product.name: Precision T3610
  dmi.product.sku: 05D2
  dmi.product.version: 00
  dmi.sys.vendor: Dell Inc.

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