As stated in QEMU 6 

Can test currently with:

`-e CPU=max \`

```
[user@hostname ~]$ qemu-system-x86_64 -cpu help
x86 Penryn                (alias configured by machine type)                        
x86 Penryn-v1             Intel Core 2 Duo P9xxx (Penryn Class Core 2)              
...
x86 base                  base CPU model type with no features enabled              
x86 host                  KVM processor with all supported host features            
x86 max                   Enables all features supported by the accelerator in the current host
```

See sickcodes#304