[PATCH v3 06/10] KVM: nVMX: Switch to vmcs01 to update SVI on-demand if L2 is active

[Sean Christopherson <seanjc@google.com>]

If APICv is activated while L2 is running and triggers an SVI update,
temporarily load vmcs01 and immediately update SVI instead of deferring
the update until the next nested VM-Exit.  This will eventually allow
killing off kvm_apic_update_hwapic_isr(), and all of nVMX's deferred
APICv updates.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/vmx/nested.c |  5 -----
 arch/x86/kvm/vmx/vmx.c    | 19 +++++++------------
 arch/x86/kvm/vmx/vmx.h    |  1 -
 3 files changed, 7 insertions(+), 18 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 8efab1cf833f..c2c96e4fe20e 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -5160,11 +5160,6 @@ void __nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 vm_exit_reason,
 		vmx_refresh_apicv_exec_ctrl(vcpu);
 	}
 
-	if (vmx->nested.update_vmcs01_hwapic_isr) {
-		vmx->nested.update_vmcs01_hwapic_isr = false;
-		kvm_apic_update_hwapic_isr(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 3ee86665d8de..74a815cddd37 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6963,21 +6963,16 @@ void vmx_hwapic_isr_update(struct kvm_vcpu *vcpu, int max_isr)
 	u16 status;
 	u8 old;
 
-	/*
-	 * If L2 is active, defer the SVI update until vmcs01 is loaded, as SVI
-	 * is only relevant for if and only if Virtual Interrupt Delivery is
-	 * enabled in vmcs12, and if VID is enabled then L2 EOIs affect L2's
-	 * vAPIC, not L1's vAPIC.  KVM must update vmcs01 on the next nested
-	 * VM-Exit, otherwise L1 with run with a stale SVI.
-	 */
-	if (is_guest_mode(vcpu)) {
-		to_vmx(vcpu)->nested.update_vmcs01_hwapic_isr = true;
-		return;
-	}
-
 	if (max_isr == -1)
 		max_isr = 0;
 
+	/*
+	 * Always update SVI in vmcs01, as SVI is only relevant for L2 if and
+	 * only if Virtual Interrupt Delivery is enabled in vmcs12, and if VID
+	 * is enabled then L2 EOIs affect L2's vAPIC, not L1's vAPIC.
+	 */
+	guard(vmx_vmcs01)(vcpu);
+
 	status = vmcs_read16(GUEST_INTR_STATUS);
 	old = status >> 8;
 	if (max_isr != old) {
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 36f48c4b39c0..53969e49d9d1 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -134,7 +134,6 @@ struct nested_vmx {
 	bool change_vmcs01_virtual_apic_mode;
 	bool reload_vmcs01_apic_access_page;
 	bool update_vmcs01_apicv_status;
-	bool update_vmcs01_hwapic_isr;
 
 	/*
 	 * Enlightened VMCS has been enabled. It does not mean that L1 has to
-- 
2.52.0.223.gf5cc29aaa4-goog