[PATCH v4 5/8] KVM: nVMX: Switch to vmcs01 to refresh APICv controls on-demand if L2 is active

[Sean Christopherson <seanjc@google.com>]

If APICv is (un)inhibited while L2 is running, temporarily load vmcs01 and
immediately refresh the APICv controls in vmcs01 instead of deferring the
update until the next nested VM-Exit.  This all but eliminates potential
ordering issues due to vmcs01 not being synchronized with
kvm_lapic.apicv_active, e.g. where KVM _thinks_ it refreshed APICv, but
vmcs01 still contains stale state.

Reviewed-by: Chao Gao <chao.gao@intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/vmx/nested.c | 5 -----
 arch/x86/kvm/vmx/vmx.c    | 5 +----
 arch/x86/kvm/vmx/vmx.h    | 1 -
 3 files changed, 1 insertion(+), 10 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index c2c96e4fe20e..2b0702349aa1 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -5155,11 +5155,6 @@ void __nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 vm_exit_reason,
 		kvm_make_request(KVM_REQ_APIC_PAGE_RELOAD, vcpu);
 	}
 
-	if (vmx->nested.update_vmcs01_apicv_status) {
-		vmx->nested.update_vmcs01_apicv_status = false;
-		vmx_refresh_apicv_exec_ctrl(vcpu);
-	}
-
 	if ((vm_exit_reason != -1) &&
 	    (enable_shadow_vmcs || nested_vmx_is_evmptr12_valid(vmx)))
 		vmx->nested.need_vmcs12_to_shadow_sync = true;
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 74a815cddd37..90e167f296d0 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -4578,10 +4578,7 @@ void vmx_refresh_apicv_exec_ctrl(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 
-	if (is_guest_mode(vcpu)) {
-		vmx->nested.update_vmcs01_apicv_status = true;
-		return;
-	}
+	guard(vmx_vmcs01)(vcpu);
 
 	pin_controls_set(vmx, vmx_pin_based_exec_ctrl(vmx));
 
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 53969e49d9d1..dfc9766a7fa3 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -133,7 +133,6 @@ struct nested_vmx {
 
 	bool change_vmcs01_virtual_apic_mode;
 	bool reload_vmcs01_apic_access_page;
-	bool update_vmcs01_apicv_status;
 
 	/*
 	 * Enlightened VMCS has been enabled. It does not mean that L1 has to
-- 
2.52.0.457.g6b5491de43-goog