[Bug 1900241] Re: [regression][powerpc] some vcpus are found offline inside guest with different vsmt setting from qemu-cmdline and breaks subsequent vcpu hotplug operation (xive)

[Greg Kurz <1900241@bugs.launchpad.net>]

Fixed by reverting the series that caused the regression.

https://git.qemu.org/?p=qemu.git;a=commit;h=6d24795ee7e3199d199d3c415312c93382ad1807

The optimization needs to be reworked later.


** Changed in: qemu
       Status: New => Fix Committed

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Title:
  [regression][powerpc] some vcpus are found offline inside guest with
  different vsmt setting from qemu-cmdline and breaks subsequent vcpu
  hotplug operation (xive)

Status in QEMU:
  Fix Committed

Bug description:
  Env:
  Host: Power9 HW ppc64le

  # lscpu
  Architecture:                    ppc64le
  Byte Order:                      Little Endian
  CPU(s):                          128
  On-line CPU(s) list:             24-31,40-159
  Thread(s) per core:              4
  Core(s) per socket:              16
  Socket(s):                       2
  NUMA node(s):                    2
  Model:                           2.3 (pvr 004e 1203)
  Model name:                      POWER9, altivec supported
  Frequency boost:                 enabled
  CPU max MHz:                     3800.0000
  CPU min MHz:                     2300.0000
  L1d cache:                       1 MiB
  L1i cache:                       1 MiB
  L2 cache:                        8 MiB
  L3 cache:                        160 MiB
  NUMA node0 CPU(s):               24-31,40-79
  NUMA node8 CPU(s):               80-159
  Vulnerability Itlb multihit:     Not affected
  Vulnerability L1tf:              Mitigation; RFI Flush, L1D private per thread
  Vulnerability Mds:               Not affected
  Vulnerability Meltdown:          Mitigation; RFI Flush, L1D private per thread
  Vulnerability Spec store bypass: Mitigation; Kernel entry/exit barrier (eieio)
  Vulnerability Spectre v1:        Mitigation; __user pointer sanitization, ori31 speculation barrier enabled
  Vulnerability Spectre v2:        Mitigation; Software count cache flush (hardware accelerated), Software link stack flush
  Vulnerability Srbds:             Not affected
  Vulnerability Tsx async abort:   Not affected


  Host Kernel: 5.9.0-0.rc8.28.fc34.ppc64le (Fedora rawhide)
  Guest Kernel: Fedora33(5.8.6-301.fc33.ppc64le)

  Qemu: e12ce85b2c79d83a340953291912875c30b3af06 (qemu/master)

  
  Steps to reproduce:

  Boot below kvm guest: (-M pseries,vsmt=2 -smp 8,cores=8,threads=1)

   /home/sath/qemu/build/qemu-system-ppc64 -name vm1 -M pseries,vsmt=2
  -accel kvm -m 4096  -smp 8,cores=8,threads=1 -nographic -nodefaults
  -serial mon:stdio -vga none -nographic -device virtio-scsi-pci -drive
  file=/home/sath/tests/data/avocado-vt/images/fdevel-
  ppc64le.qcow2,if=none,id=hd0,format=qcow2,cache=none -device scsi-
  hd,drive=hd0

  
  lscpu inside guest:
  Actual:
  [root@atest-guest ~]# lscpu
  Architecture:                    ppc64le
  Byte Order:                      Little Endian
  CPU(s):                          8
  On-line CPU(s) list:             0,2,4,6
  Off-line CPU(s) list:            1,3,5,7 --------------------------NOK
  Thread(s) per core:              1
  Core(s) per socket:              4
  Socket(s):                       1
  NUMA node(s):                    1
  Model:                           2.3 (pvr 004e 1203)
  Model name:                      POWER9 (architected), altivec supported
  Hypervisor vendor:               KVM
  Virtualization type:             para
  L1d cache:                       128 KiB
  L1i cache:                       128 KiB
  NUMA node0 CPU(s):               0,2,4,6
  Vulnerability Itlb multihit:     Not affected
  Vulnerability L1tf:              Mitigation; RFI Flush, L1D private per thread
  Vulnerability Mds:               Not affected
  Vulnerability Meltdown:          Mitigation; RFI Flush, L1D private per thread
  Vulnerability Spec store bypass: Mitigation; Kernel entry/exit barrier (eieio)
  Vulnerability Spectre v1:        Mitigation; __user pointer sanitization, ori31 
                                   speculation barrier enabled
  Vulnerability Spectre v2:        Mitigation; Software count cache flush (hardwar
                                   e accelerated), Software link stack flush
  Vulnerability Srbds:             Not affected
  Vulnerability Tsx async abort:   Not affected

  
  Expected:

  [root@atest-guest ~]# lscpu
  Architecture:                    ppc64le
  Byte Order:                      Little Endian
  CPU(s):                          8
  On-line CPU(s) list:             0-7
  Thread(s) per core:              1
  Core(s) per socket:              8
  Socket(s):                       1
  NUMA node(s):                    1
  Model:                           2.3 (pvr 004e 1203)
  Model name:                      POWER9 (architected), altivec supported
  Hypervisor vendor:               KVM
  Virtualization type:             para
  L1d cache:                       256 KiB
  L1i cache:                       256 KiB
  NUMA node0 CPU(s):               0-7
  Vulnerability Itlb multihit:     Not affected
  Vulnerability L1tf:              Mitigation; RFI Flush, L1D private per thread
  Vulnerability Mds:               Not affected
  Vulnerability Meltdown:          Mitigation; RFI Flush, L1D private per thread
  Vulnerability Spec store bypass: Mitigation; Kernel entry/exit barrier (eieio)
  Vulnerability Spectre v1:        Mitigation; __user pointer sanitization, ori31 
                                   speculation barrier enabled
  Vulnerability Spectre v2:        Mitigation; Software count cache flush (hardwar
                                   e accelerated), Software link stack flush
  Vulnerability Srbds:             Not affected
  Vulnerability Tsx async abort:   Not affected


  There by further vcpuhotplug operation fails...

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