WARN and reject nested VM-Enter if KVM is using eVMCS and manages to allow a non-zero value in the upper 32 bits of VM-function controls. The eVMCS code assumes all inputs are 32-bit values and subtly drops the upper bits. WARN instead of adding proper "support", it's unlikely the upper bits will be defined/used in the next decade. Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> --- arch/x86/kvm/vmx/evmcs.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/arch/x86/kvm/vmx/evmcs.c b/arch/x86/kvm/vmx/evmcs.c index ce358b13b75b..bd1dcc077c85 100644 --- a/arch/x86/kvm/vmx/evmcs.c +++ b/arch/x86/kvm/vmx/evmcs.c @@ -486,6 +486,14 @@ int nested_evmcs_check_controls(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12) vmcs12->vm_entry_controls))) return -EINVAL; + /* + * VM-Func controls are 64-bit, but KVM currently doesn't support any + * controls in bits 63:32, i.e. dropping those bits on the consistency + * check is intentional. + */ + if (WARN_ON_ONCE(vmcs12->vm_function_control >> 32)) + return -EINVAL; + if (CC(!nested_evmcs_is_valid_controls(vcpu, EVMCS_VMFUNC, vmcs12->vm_function_control))) return -EINVAL; -- 2.37.1.595.g718a3a8f04-goog
