Re: [PATCH 2/2] kvm: nVMX: Introduce KVM_CAP_STATE

From: Paolo Bonzini
Date: Fri Apr 27 2018 - 06:03:36 EST

On 27/04/2018 00:28, Jim Mattson wrote:
> The other thing that comes to mind is that there are some new fields
> in the VMCS12 since I first implemented this. One potentially
> troublesome field is the VMX preemption timer. If the current timer
> value is not saved on VM-exit, then it won't be stashed in the shadow
> VMCS12 by sync_vmcs12. Post-migration, the timer will be reset to its
> original value.
> Do we care? Is this any different from what happens on real hardware
> when there's an SMI? According to the SDM, this appears to be exacty
> what happens when the dual-monitor treatment of SMIs and SMM is
> active, but it's not clear what happens with the default treatment of
> SMIs and SMM.

I think it should be the same, because the preemption timer countdown is
not part of the VMX-critical state.