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

From: Thomas Huth
Subject: [Bug 1788275] Re: -cpu ...,+topoext works only with EPYC CPU model
Date: Fri, 13 Nov 2020 15:46:28 -0000

The QEMU project is currently considering to move its bug tracking to another 
system. For this we need to know which bugs are still valid and which could be 
closed already. Thus we are setting older bugs to "Incomplete" now.
If you still think this bug report here is valid, then please switch the state 
back to "New" within the next 60 days, otherwise this report will be marked as 
"Expired". Or mark it as "Fix Released" if the problem has been solved with a 
newer version of QEMU already. Thank you and sorry for the inconvenience.

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

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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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