Re: x86_64 emulation on ppc64le POWER9 hardware - no multi threading

[Cédric Le Goater]

On 8/17/20 10:29 AM, Kim-Norman Sahm wrote:
> Hi Cedric,
> 
> additional: which qemu and libvirt versions are you using?
I am using the ones installed on 20.04.

ii  qemu-system-x86                      1:4.2-3ubuntu6.3                      
ppc64el      QEMU full system emulation binaries (x86)
ii  libvirt0:ppc64el                     6.0.0-0ubuntu8.3                      
ppc64el      library for interfacing with different virtualization systems

Cheers,

C.

> 
> Mit freundlichen Grüßen / Best regards,
>  
> Kim-Norman Sahm
> Chief Technology Officer
>  
> Tel.: +49 151/46257663
> Email: kim-norman.sahm@cloudical.io
>  
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> Am 06.08.20, 08:15 schrieb "Kim-Norman Sahm" <kim-norman.sahm@cloudical.io>:
> 
>     Hi Cedric,
> 
>     could you send me your complete xml file?
>     I get the error: process exited while connecting to monitor: 
> 2020-08-03T17:43:50.146851Z qemu-system-x86_64: The -accel and "-machine 
> accel=" options are incompatible.
> 
>     Best regards
>     KIm
> 
>     Am 03.08.20, 19:37 schrieb "Cédric Le Goater" <clg@kaod.org>:
> 
>         Again, with a correct answer,
> 
>         On 8/3/20 3:47 PM, Kim-Norman Sahm wrote:
>         > hi,
>         > 
>         >  
>         > 
>         > i’m running Debian 10 on POWER9 and would like to spawn x86_64 
> emulated VMs.
>         > 
>         > The virtual machine is configured to run with 8 vpus but it’s very 
> slow.
>         > 
>         > On the host you can see that the qemu-system-x86_64 process is 
> using just one core!
>         > 
>         >  
>         > 
>         > Ppc64le guests are using multi cores, so its looks like an config 
> problem or software bug with the x86 emulator.
> 
>         On a Power9 host (20.04), I did the following changes to an x86 
> domain :
> 
>           <domain type='qemu' 
> xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>
> 
>         and at the end of the domain file  :
>           <qemu:commandline>
>             <qemu:arg value='-accel'/>
>             <qemu:arg value='tcg,thread=multi'/>
>           </qemu:commandline>
> 
>         The topology is defined as : 
> 
>           <cpu mode='custom' match='exact' check='none'>
>             <model fallback='forbid'>qemu64</model>
>             <topology sockets='1' cores='12' threads='2'/>
>           </cpu>
> 
>         The VM is using MTTCG, as reported by top on the host :
> 
>             PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     
> TIME+ COMMAND
>         5761 libvirt+  20   0   23.5g   1.8g  21888 R  2167   1.4   6:10.82 
> qemu-system-x86
> 
>         In the guest :
> 
>         $ lscpu 
>         Architecture:                    x86_64
>         CPU op-mode(s):                  32-bit, 64-bit
>         Byte Order:                      Little Endian
>         Address sizes:                   40 bits physical, 48 bits virtual
>         CPU(s):                          24
>         On-line CPU(s) list:             0-23
>         Thread(s) per core:              1
>         Core(s) per socket:              24
>         Socket(s):                       1
>         NUMA node(s):                    1
>         Vendor ID:                       AuthenticAMD
>         CPU family:                      6
>         Model:                           6
>         Model name:                      QEMU Virtual CPU version 2.1.0
>         Stepping:                        3
>         CPU MHz:                         511.035
>         BogoMIPS:                        1022.07
>         Virtualization:                  AMD-V
>         L1d cache:                       1.5 MiB
>         L1i cache:                       1.5 MiB
>         L2 cache:                        12 MiB
>         NUMA node0 CPU(s):               0-23
>         Vulnerability L1tf:              Not affected
>         Vulnerability Mds:               Not affected
>         Vulnerability Meltdown:          Not affected
>         Vulnerability Spec store bypass: Vulnerable
>         Vulnerability Spectre v1:        Mitigation; usercopy/swapgs barriers 
> and __user
>                                           pointer sanitization
>         Vulnerability Spectre v2:        Mitigation; Full generic retpoline, 
> STIBP disab
>                                          led, RSB filling
>         Flags:                           fpu de pse tsc msr pae mce cx8 apic 
> sep mtrr pg
>                                          e mca cmov pat pse36 clflush mmx 
> fxsr sse sse2 
>                                          ht syscall nx lm nopl cpuid pni cx16 
> popcnt hyp
>                                          ervisor lahf_lm cmp_legacy svm abm 
> sse4a 3dnowp
>                                          refetch vmmcall
> 
> 
>         Cheers,
> 
>         C. 
> 
>