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[Bug 1788275] Re: -cpu ...,+topoext works only with EPYC CPU model

From: Launchpad Bug Tracker
Subject: [Bug 1788275] Re: -cpu ...,+topoext works only with EPYC CPU model
Date: Wed, 13 Jan 2021 04:17:17 -0000

[Expired for QEMU because there has been no activity for 60 days.]

** Changed in: qemu
       Status: Incomplete => Expired

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  -cpu ...,+topoext works only with EPYC CPU model

Status in QEMU:

Bug description:
  See bug report at:

  Probably this is caused by the inconsistent legacy cache information
  on all CPU models except EPYC.

  Description of problem:
  Guest should get 2 threads per core and all of them should be on-line when 
booting guest with old amd cpu model + smt

  Steps to Reproduce:
  1.Boot rhel7.6 guest with cli:
  /usr/libexec/qemu-kvm -name rhel7.6 -m 16G -machine pc,accel=kvm \
          -S \
          -cpu Opteron_G3,+topoext,xlevel=0x8000001e,enforce \
          -smp 2,threads=2 \
          -monitor stdio \
          -qmp unix:/tmp/qmp2,server,nowait \
          -device VGA \
          -vnc :0 \
          -serial unix:/tmp/console2,server,nowait \
          -uuid 115e11b2-a869-41b5-91cd-6a32a907be7f \
 -device ide-hd,drive=drive-scsi-disk0,id=scsi-disk0 \
          -netdev tap,id=idinWyYY,vhost=on -device 
virtio-net-pci,mac=2e:39:fa:ff:88:a1,id=idlbq7eA,netdev=idinWyYY \

  2.check cpu info inside guest

  Actual results:
  Guest gets one online cpu, one offline cpu and one thread per core:
  # lscpu
  Architecture:          x86_64
  CPU op-mode(s):        32-bit, 64-bit
  Byte Order:            Little Endian
  CPU(s):                2
  On-line CPU(s) list:   0
  Off-line CPU(s) list:  1
  Thread(s) per core:    1
  Core(s) per socket:    1
  Socket(s):             1
  NUMA node(s):          1
  Vendor ID:             AuthenticAMD
  CPU family:            16
  Model:                 2
  Model name:            AMD Opteron 23xx (Gen 3 Class Opteron)
  Stepping:              3
  CPU MHz:               2096.060
  BogoMIPS:              4192.12
  Hypervisor vendor:     KVM
  Virtualization type:   full
  L1d cache:             64K
  L1i cache:             64K
  L2 cache:              512K
  L3 cache:              16384K
  NUMA node0 CPU(s):     0
  Flags:                 fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge 
mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx lm art rep_good nopl 
extd_apicid pni cx16 x2apic popcnt hypervisor lahf_lm cmp_legacy abm sse4a 
misalignsse topoext retpoline_amd ibp_disable vmmcall

  Expected results:
  Guest should get 2 threads per core and all of them should be on-line


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