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

[Kim-Norman Sahm]

Hi Cedric,

additional: which qemu and libvirt versions are you using?

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.