[Bug 1920784] Re: qemu-system-ppc64le fails with kvm acceleration

["Christian Ehrhardt " <1920784@bugs.launchpad.net>]

Since this seems to be broken on all Distributions as soon as the triggering
combination of kernel/glibc is present I think we'd want to open that up to
upstream qemu for a wider discussion and to also hit the ppc64 architecture
experts.

Furthermore I'm not entirely sure if this needs to be fixed in qemu, it
might instead be the case that instead a fix is needed in glibc.

Therefore I'm adding a qemu (upstream) bug task for now to have the bug
reported there as well (might be worth for awareness anyway) - but
chances are that after some debugging it will turn out to become a glibc
issue instead.

If only I could break this test out of kvm ioctl into something simpler,
then we could then properly file against glibc ....

** Also affects: glibc (Ubuntu)
   Importance: Undecided
       Status: New

** Also affects: qemu
   Importance: Undecided
       Status: New

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https://bugs.launchpad.net/bugs/1920784

Title:
  qemu-system-ppc64le fails with kvm acceleration

Status in QEMU:
  New
Status in The Ubuntu-power-systems project:
  New
Status in glibc package in Ubuntu:
  New
Status in qemu package in Ubuntu:
  Confirmed

Bug description:
  (Suspected glibc issue!)

  qemu-system-ppc64(le) fails when invoked with kvm acceleration with
  error "illegal instruction"

  > qemu-system-ppc64(le) -M pseries,accel=kvm

  Illegal instruction (core dumped)

  In dmesg:

  Facility 'SCV' unavailable (12), exception at 0x7624f8134c0c,
  MSR=900000000280f033

  
  Version-Release number of selected component (if applicable):
  qemu 5.2.0 
  Linux kernel 5.11
  glibc 2.33
  all latest updates as of submitting the bug report

  How reproducible:
  Always

  Steps to Reproduce:
  1. Run qemu with kvm acceleration

  Actual results:
  Illegal instruction

  Expected results:
  Normal VM execution

  Additional info:
  The machine is a Raptor Talos II Lite with a Sforza V1 8-core, but was also observed on a Raptor Blackbird with the same processor.

  This was also observed on Fedora 34 beta, which uses glibc 2.33
  Also tested on ArchPOWER (unofficial port of Arch Linux for ppc64le) with glibc 2.33
  Fedora 33 and Ubuntu 20.10, both using glibc 2.32 do not have this issue, and downgrading the Linux kernel from 5.11 to 5.4 LTS on ArchPOWER solved the problem. Kernel 5.9 and 5.10 have the same issue when combined with glibc2.33

  ProblemType: Bug
  DistroRelease: Ubuntu 21.04
  Package: qemu-system 1:5.2+dfsg-6ubuntu2
  ProcVersionSignature: Ubuntu 5.11.0-11.12-generic 5.11.0
  Uname: Linux 5.11.0-11-generic ppc64le
  .sys.firmware.opal.msglog: Error: [Errno 13] Permission denied: '/sys/firmware/opal/msglog'
  ApportVersion: 2.20.11-0ubuntu60
  Architecture: ppc64el
  CasperMD5CheckResult: pass
  CurrentDesktop: Unity:Unity7:ubuntu
  Date: Mon Mar 22 14:48:39 2021
  InstallationDate: Installed on 2021-03-22 (0 days ago)
  InstallationMedia: Ubuntu-Server 21.04 "Hirsute Hippo" - Alpha ppc64el (20210321)
  KvmCmdLine: COMMAND         STAT  EUID  RUID     PID    PPID %CPU COMMAND
  ProcKernelCmdLine: root=UUID=f3d03315-0944-4a02-9c87-09c00eba9fa1 ro
  ProcLoadAvg: 1.20 0.73 0.46 1/1054 6071
  ProcSwaps:
   Filename				Type		Size		Used		Priority
   /swap.img                               file		8388544		0		-2
  ProcVersion: Linux version 5.11.0-11-generic (buildd@bos02-ppc64el-002) (gcc (Ubuntu 10.2.1-20ubuntu1) 10.2.1 20210220, GNU ld (GNU Binutils for Ubuntu) 2.36.1) #12-Ubuntu SMP Mon Mar 1 19:26:20 UTC 2021
  SourcePackage: qemu
  UpgradeStatus: No upgrade log present (probably fresh install)
  VarLogDump_list: total 0
  acpidump:
   
  cpu_cores: Number of cores present = 8
  cpu_coreson: Number of cores online = 8
  cpu_smt: SMT=4

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