On 08/01/2018 17:48, Dr. David Alan Gilbert wrote: >> If your hypervisor is lying to you about the primary family, then all >> bets are off. I don't expect there will be any production systems doing >> this. > It's not that an unusual thing to do on qemu/kvm - to specify the lowest > common denominator of the set of CPUs in your data centre (for any one > vendor); it does tend to get some weird combinations.
Agreed. But on a hypervisor we pretty much know that: - the MSR_AMD64_DE_CFG doesn't exist unless you have a fix - setting the MSR_AMD64_DE_CFG bit to 1 if you have a fix can be done independent of the family So all KVM needs is a X86_FEATURE_LFENCE_SERIALIZE, it doesn't matter if it's because of the family or because Linux has set MSR_F10H_DE_CFG. The guest will either try setting the MSR bit and #GP, or it will find it already set and do nothing. Of course no code for this has been written yet. Paolo
