Re: [PATCH v9 17/22] KVM: x86: Advertise support for FRED

[Xin Li]

>>> 
>>> In this case, we need to clear FRED for AMD.
>>> 
>>> The concern is that before AMD's FRED KVM support is implemented, FRED will be
>>> exposed to userspace on AMD FRED-capable hardware. This may cause issues.
>> 
>> Hmm, I think it’s Qemu does that.
>> 
>> We have 2 filters, one in Qemu and one in KVM, only both are set a feature is enabled.
>> 
>> What I have missed?
> 
> If a newer QEMU (with AMD's FRED support patch) + an older KVM (without AMD's
> FRED support, but KVM advertises it), it may cause issues.
> 
> I guess it's no safety issue for host though, AMD should also require some
> control bit(s) to be set to allow guests to use the feature.
> 
> I agree with Chao that it should be cleared for AMD before AMD's FRED KVM
> support is implemented.


Damn, I somehow thought the host won’t report FRED on AMD...