On 02/05/2018 17:52, Jim Mattson wrote: >>> vmcs_field_readonly is now unused. With that removed, >>> >>> Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> >> Actually, no. The error must be kept if the host has disabled the >> feature with a KVM_SET_MSR ioctl for MSR_IA32_VMX_MISC. >> > Coming back to this patch set... > > Is there a good reason to allow userspace to clear > MSR_IA32_VMX_MISC_VMWRITE_SHADOW_RO_FIELDS? It's not yet possible to > migrate a VMX-capable VM (though I think that ability is imminent), so > there are no compatibility issues. Why not just force this on? I suppose that can be done, yes. The only reason is that silicon ties that bit to the availability of shadow VMCS, but we can certainly do things differently than actual processors. Technically it would be a small userspace API break, but we can live with it. Paolo
