A minor optimization to WRMSR MSR_IA32_RTIT_CTL when necessary. Opportunistically refine the comment to call out that KVM requires VM_EXIT_CLEAR_IA32_RTIT_CTL to expose PT to the guest. Reviewed-by: Sean Christopherson <seanjc@xxxxxxxxxx> Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx> --- Changes in v2: - Refine comments --- arch/x86/kvm/vmx/vmx.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index fada1055f325..5535a86aea37 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -1074,8 +1074,12 @@ static void pt_guest_exit(struct vcpu_vmx *vmx) pt_load_msr(&vmx->pt_desc.host, vmx->pt_desc.addr_range); } - /* Reload host state (IA32_RTIT_CTL will be cleared on VM exit). */ - wrmsrl(MSR_IA32_RTIT_CTL, vmx->pt_desc.host.ctl); + /* + * KVM requires VM_EXIT_CLEAR_IA32_RTIT_CTL to expose PT to the guest, + * i.e. RTIT_CTL is always cleared on VM-Exit. Restore it if necessary. + */ + if (vmx->pt_desc.host.ctl) + wrmsrl(MSR_IA32_RTIT_CTL, vmx->pt_desc.host.ctl); } void vmx_set_host_fs_gs(struct vmcs_host_state *host, u16 fs_sel, u16 gs_sel, -- 2.27.0
