[Qemu-devel] [Bug 1788275] [NEW] -cpu ..., +topoext works only with EPYC CPU model

[Eduardo Habkost]

Public bug reported:

See bug report at:
https://bugzilla.redhat.com/show_bug.cgi?id=1615682

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 \
        -drive 
file=rhel7.6-20180812.qcow2,if=none,id=drive-scsi-disk0,format=qcow2,cache=none,werror=stop,rerror=stop
 -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
3.

Actual results:
Guest gets one online cpu, one offline cpu and one thread per core:
# lscpu
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

---------------------------------------------

** Affects: qemu
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1788275

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

Status in QEMU:
  New

Bug description:
  See bug report at:
  https://bugzilla.redhat.com/show_bug.cgi?id=1615682

  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 \
          -drive 
file=rhel7.6-20180812.qcow2,if=none,id=drive-scsi-disk0,format=qcow2,cache=none,werror=stop,rerror=stop
 -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
  3.

  Actual results:
  Guest gets one online cpu, one offline cpu and one thread per core:
  # lscpu
  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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