Re: [PATCH] KVM: nVMX: Filter out all unsupported controls when eVMCS was activated

[Paolo Bonzini]

On 09/09/21 09:03, Vitaly Kuznetsov wrote:
> Sean Christopherson <seanjc@xxxxxxxxxx> writes:
>
> > On Tue, Sep 07, 2021, Vitaly Kuznetsov wrote:
> > > Let's be bold this time and instead of playing whack-a-mole just filter out
> > > all unsupported controls from VMX MSRs.
> >
> > Out of curiosity, why didn't we do this from the get-go?
>
> We actually did, the initial implementation (57b119da3594f) was
> filtering out everything but then things changed in "only clear controls
> which are known to cause issues" (31de3d2500e4). I forgot everything
> already but was able to google this suggestion from Paolo:
>
> https://www.lkml.org/lkml/2020/1/22/1108

The doubt was whether userspaces could be enabling eVMCS blindly, and 
thus would lose features for Linux guests.

Paolo