Re: [PATCH] KVM/VMX: Invoke NMI non-IST entry instead of IST entry

[Sean Christopherson]

On Tue, May 04, 2021, Paolo Bonzini wrote:
> On 04/05/21 23:05, Maxim Levitsky wrote:
> > Does this mean that we still rely on hardware NMI masking to be activated?
> 
> No, the NMI code already handles reentrancy at both the assembly and C
> levels.
> 
> > Or in other words, that is we still can't have an IRET between VM exit and
> > the entry to the NMI handler?
> 
> No, because NMIs are not masked on VM exit.  This in fact makes things
> potentially messy; unlike with AMD's CLGI/STGI, only MSRs and other things
> that Intel thought can be restored atomically with the VM exit.

FWIW, NMIs are masked if the VM-Exit was due to an NMI.