On Tue, Nov 29, 2016 at 12:01 AM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: >> 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. I already wrote the patch, so unless there's an argument against removing them I'll include it in the next patchset. Thanks! > >> > >> >> 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
