Save BNDCFGS to vmcs12 (from vmcs02) if and only if at least of one of the load-on-entry or clear-on-exit fields for BNDCFGS is enumerated as an allowed-1 bit in vmcs12. Skipping the field avoids an unnecessary VMREAD when MPX is supported but not exposed to L1. Per Intel's SDM: If the processor supports either the 1-setting of the "load IA32_BNDCFGS" VM-entry control or that of the "clear IA32_BNDCFGS" VM-exit control, the contents of the IA32_BNDCFGS MSR are saved into the corresponding field. Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> --- arch/x86/kvm/vmx/nested.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 38015f4ecc54..496981b86f94 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -4104,7 +4104,8 @@ static void sync_vmcs02_to_vmcs12_rare(struct kvm_vcpu *vcpu, vmcs12->guest_idtr_base = vmcs_readl(GUEST_IDTR_BASE); vmcs12->guest_pending_dbg_exceptions = vmcs_readl(GUEST_PENDING_DBG_EXCEPTIONS); - if (kvm_mpx_supported()) + if ((vmx->nested.msrs.entry_ctls_high & VM_ENTRY_LOAD_BNDCFGS) || + (vmx->nested.msrs.exit_ctls_high & VM_EXIT_CLEAR_BNDCFGS)) vmcs12->guest_bndcfgs = vmcs_read64(GUEST_BNDCFGS); vmx->nested.need_sync_vmcs02_to_vmcs12_rare = false; -- 2.36.1.476.g0c4daa206d-goog
