nova get_capabilities should not use host capabilities

[HYSong]

Nova-compute will configure Broadwell-IBRS's features if using host capabilities by the function of get_capabilities, but the VM's real features is depend on the model of Broadwell-IBRS when cpu_mode is configured to host-model in nova.conf.

I think it is unreasonable because nova will use host capabilities to compare CPU when host-model cpu mode is configured in nova.conf. But the actual VM's model may different from host model, and it was selected by Libvirt. It is likely lead to live migrate ERROR because of using wrong cpu futures.

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root@cmp004:~# qemu-system-x86_64 --version
QEMU emulator version 2.11.1(Debian 1:2.11+dfsg-1.4~u16.04+mcp2)
Copyright (c) 2003-2017 Fabrice Bellard and the QEMU Project developers

root@cmp004:~# libvirtd -V
libvirtd (libvirt) 4.0.0

openstack version: queens

root@cmp004:~# virsh domcapabilities
<domainCapabilities>
  <cpu>
    <mode name='host-model' supported='yes'>
      <model fallback='forbid'>Skylake-Client-IBRS</model>
      <vendor>Intel</vendor>
      <feature policy='require' name='ss'/>
      <feature policy='require' name='vmx'/>
      <feature policy='require' name='hypervisor'/>
      <feature policy='require' name='tsc_adjust'/>
      <feature policy='require' name='ssbd'/>
      <feature policy='require' name='pdpe1gb'/>
      <feature policy='require' name='invtsc'/>
      <feature policy='disable' name='mpx'/>
      <feature policy='disable' name='xsavec'/>
      <feature policy='disable' name='xgetbv1'/>
    </mode>
  </cpu>
</domainCapabilities>

root@cmp004:~# virsh capabilities
<capabilities>
  <host>
    <cpu>
      <arch>x86_64</arch>
      <model>Broadwell-IBRS</model>
      <vendor>Intel</vendor>
      <microcode version='184549422'/>
      <topology sockets='1' cores='8' threads='2'/>
      <feature name='vme'/>
      <feature name='ds'/>
      <feature name='acpi'/>
      <feature name='ss'/>
      <feature name='ht'/>
      <feature name='tm'/>
      <feature name='pbe'/>
      <feature name='dtes64'/>
      <feature name='monitor'/>
      <feature name='ds_cpl'/>
      <feature name='vmx'/>
      <feature name='smx'/>
      <feature name='est'/>
      <feature name='tm2'/>
      <feature name='xtpr'/>
      <feature name='pdcm'/>
      <feature name='dca'/>
      <feature name='osxsave'/>
      <feature name='f16c'/>
      <feature name='rdrand'/>
      <feature name='arat'/>
      <feature name='tsc_adjust'/>
      <feature name='cmt'/>
      <feature name='ssbd'/>
      <feature name='xsaveopt'/>
      <feature name='mbm_total'/>
      <feature name='mbm_local'/>
      <feature name='pdpe1gb'/>
      <feature name='abm'/>
      <feature name='invtsc'/>
      <pages unit='KiB' size='4'/>
      <pages unit='KiB' size='1048576'/>
    </cpu>
  </host>
<capabilities>

root@ctl01:~# nova hypervisor-show c8f34226-c2e9-4c09-bdbe-aaaff1a1d370
+---------------------------+------------------------------------------+
| Property | Value |
+---------------------------+------------------------------------------+
| cpu_info_arch | x86_64 |
| cpu_info_features | ["pge", "avx", "xsaveopt", "clflush", |
| | "sep", "rtm", "tsc_adjust", "tsc- |
| | deadline", "dtes64", "invpcid", "tsc", |
| | "fsgsbase", "xsave", "smap", "vmx", |
| | "erms", "xtpr", "cmov", "hle", "smep", |
| | "ssse3", "est", "pat", "monitor", "smx", |
| | "pbe", "lm", "msr", "adx", |
| | "3dnowprefetch", "nx", "fxsr", |
| | "syscall", "tm", "sse4.1", "pae", |
| | "sse4.2", "pclmuldq", "cx16", "pcid", |
| | "fma", "vme", "popcnt", "mmx", |
| | "osxsave", "cx8", "mce", "de", "rdtscp", |
| | "ht", "dca", "lahf_lm", "abm", "rdseed", |
| | "pdcm", "mca", "pdpe1gb", "apic", "sse", |
| | "f16c", "pse", "ds", "invtsc", "pni", |
| | "tm2", "avx2", "aes", "sse2", "ss", |
| | "ds_cpl", "arat", "bmi1", "bmi2", |
| | "acpi", "spec-ctrl", "fpu", "ssbd", |
| | "pse36", "mtrr", "movbe", "rdrand", |
| | "x2apic"] |
| cpu_info_model | Broadwell-IBRS |
| service_host | cmp004 |
| service_id | 5e04fa07-db8a-4e84-a895-411c704b9d64 |
+---------------------------+------------------------------------------+

root@cmp004:~# ps -ef |grep instance-000124b5
root 16456 10674 0 17:24 pts/12 00:00:00 grep --color=auto instance-000124b5
libvirt+ 18623 1 7 16:15 ? 00:04:59 qemu-system-x86_64 -enable-kvm -cpu Skylake-Client-IBRS,ss=on,vmx=on,hypervisor=on,tsc_adjust=on,ssbd=on,pdpe1gb=on,mpx=off,xsavec=off,xgetbv1=off ...

[Balazs Gibizer (balazs-gibizer)]

@HYSong: I'm marking this as a duplicate of https://bugs.launchpad.net/nova/+bug/1903822 If you disagree please let me know.