Similarly, it is legal for the IA32_VMX_VMFUNC MSR to report all-zero. For consistency, perhaps we should not clear the "enable VM functions" capability in the IA32_VMX_PROCBASED_CTLS2 MSR just because we do not support any VM functions. On Tue, Oct 17, 2017 at 10:35 AM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > On 17/10/2017 19:29, Jim Mattson wrote: >> Following the same line of reasoning, what if >> vmx->nested.nested_vmx_secondary_ctls_high is 0 after clearing >> SECONDARY_EXEC_ENABLE_VMFUNC? Does it make sense to report >> CPU_BASED_ACTIVATE_SECONDARY_CONTROLS if we don't actually support any >> of the secondary controls? > > All-zero is a valid value for secondary controls, so I think yes. Besides: > > 1) userspace can always get into a situation where there are no valid > secondary controls but processor-based execution controls have bit 31 as > 1-allowed; > > 2) I doubt that vmfunc can be the one bit that causes > nested_vmx_secondary_ctls_high to become zero :) > > Paolo
