> On Mon, Nov 28, 2016 at 2:48 PM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > > On 28/11/2016 22:11, David Matlack wrote: > >> > PINBASED_CTLS, PROCBASED_CTLS, EXIT_CTLS and ENTRY_CTLS can be derived > >> > from their "true" counterparts, so I think it's better to remove the > >> > "non-true" ones from struct nested_vmx (and/or add the "true" ones when > >> > missing) and make them entirely computed. But it can be done on top. > >> > >> Good point. And that would mean userspace does not need to restore the > >> non-true MSRs, right? > > > > Yes, sorry for being a bit too concise. :) > > I'll include this cleanup in the next version of the patchset since it > affects which MSRs userspace will restore. It looks like a pretty > simple patch. Don't bother removing the "non-true" registers from nested_vmx; you only need to adjust the userspace API. > > > >> KVM does not emulate MSR_IA32_VMX_BASIC[55]=0, > >> and will probably never want to. > > > > That's a separate question, MSR_IA32_VMX_BASIC[55]=0 basically means > > that the "true" capabilities are the same as the "default" capabilities. > > If userspace wanted to set it that way, KVM right now would not hide > > the "true" capability MSR, but on the other hand the nested hypervisor > > should not even notice the difference. > > KVM would also need to use the non-true MSR in place of the true MSRs > when checking VMCS12 during VM-entry. It's not necessary, userspace would set the relevant bits to 1 in the true MSRs, for both the low and high parts. If it doesn't, it's garbage in garbage out. Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
