Description of problem: QEMU has supported a "max" CPU model for many releases now, but somehow we never got it wired up into libvirt. "max" is useful for applications which don't care about live migration and just want the best CPU model possible. Normally "host" would be used but this only works for KVM. "max" is identical to "host" for KVM, while for TCG it exposes every feature TCG implements. This "max" model will be a natural choice for something like libguestfs and probably other apps too. Although RHEL does not consider TCG supported, once the "max" model is supported in libvirt upstream, it will get inherited by RHEL and likely used by applications like libguestfs. This BZ is primarily a placeholder to record need for QE testing. There is no urgent LP requirement in this area. In terms of testing, it is will likely be a case of taking an existing guest config <cpu mode="host-passthrough"/> and changing it to: <cpu mode="maximum"/> For KVM, these two should behaviour in an identical way. For TCG, "host-passthrough" is not supported, but "maximum" will expose all possible TCG features. If we do see any bugs in this case, they are likely to in fact be pre-existing TCG bugs rather than libvirt bugs.
This is merged upstream 3f1f7845756e1b65946ad189979a598069a0a0ce schemas: Add support for maximum CPU mode c32f172d123c3cbe44214571c1d9118807608ec5 qemu: wire up support for maximum CPU model 9c89cc5d6ff60122e15c086c92e93aeb5180cb6e qemu: probe for "-cpu max" support 7c1653f63a44020f8888dcde7ac3f4be615975cd cpu: wire up support for maximum CPU mode 09cbd460fbdf2e9d8dbf23020bcb4048518aa290 conf: add reporting of "maximum" CPU mode in domain caps d153c101d2e92725a4e60b7a15e3bcb812ff297f conf: define a new "maximum" CPU mode
Verify this bug with libvirt-daemon-7.4.0-1.module+el8.5.0+11218+83343022.x86_64: S1: Start KVM guest with maximum cpu mode 1. define a kvm guest with maximum cpu mode # virsh dumpxml vm1 <domain type='kvm'> ... <cpu mode='maximum' check='none'> ... 2. start guest # virsh start vm1 Domain 'vm1' started 3. check qemu command line: # ps aux|grep qemu ...-cpu max... 4. Login guest and check guest cpu info IN GUEST: # lscpu ... Model name: Intel(R) Xeon(R) CPU E3-1230 v6 @ 3.50GHz ... Flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon rep_good nopl xtopology cpuid tsc_known_freq pni pclmulqdq vmx ssse3 fma cx16 pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm 3dnowprefetch cpuid_fault invpcid_single pti ssbd ibrs ibpb stibp tpr_shadow vnmi flexpriority ept vpid ept_ad fsgsbase tsc_adjust bmi1 hle avx2 smep bmi2 erms invpcid rtm mpx rdseed adx smap clflushopt xsaveopt xsavec xgetbv1 xsaves arat umip md_clear arch_capabilities S2: Start TCG guest with maximum cpu mode 1. define a tcg guest with maximum cpu mode # virsh dumpxml vm1 <domain type='qemu'> ... <cpu mode='maximum' check='none'> ... 2. start guest # virsh start vm1 Domain 'vm1' started 3. check qemu command line: # ps aux|grep qemu ...-cpu max... 4. Login guest and check guest cpu info IN GUEST: # lscpu ... Model name: QEMU TCG CPU version 2.5+ ... Flags: fpu de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush acpi mmx fxsr sse sse2 ss syscall nx mmxext pdpe1gb rdtscp lm 3dnowext 3dnow nopl cpuid pni pclmulqdq monitor ssse3 cx16 sse4_1 sse4_2 movbe popcnt aes xsave rdrand hypervisor lahf_lm svm cr8_legacy abm sse4a vmmcall fsgsbase bmi1 smep bmi2 erms mpx adx smap clflushopt clwb xsaveopt xgetbv1 arat npt pku ospke la57
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory (virt:av bug fix and enhancement update), and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHBA-2021:4684