KVM: VMX: Enable MSR-BASED TPR shadow even if APICv is inactive

I observed that kvmvapic(to optimize flexpriority=N or AMD) is used
to boost TPR access when testing kvm-unit-test/eventinj.flat tpr case
on my haswell desktop (w/ flexpriority, w/o APICv). Commit (8d14695f9542
x86, apicv: add virtual x2apic support) disable virtual x2apic mode
completely if w/o APICv, and the author also told me that windows guest
can't enter into x2apic mode when he developed the APICv feature several
years ago. However, it is not truth currently, Interrupt Remapping and
vIOMMU is added to qemu and the developers from Intel test windows 8 can
work in x2apic mode w/ Interrupt Remapping enabled recently.

This patch enables TPR shadow for virtual x2apic mode to boost
windows guest in x2apic mode even if w/o APICv.

Can pass the kvm-unit-test.

Suggested-by: Radim Krčmář <rkrcmar@redhat.com>
Suggested-by: Wincy Van <fanwenyi0529@gmail.com>
Reviewed-by: Radim Krčmář <rkrcmar@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Wincy Van <fanwenyi0529@gmail.com>
Cc: Yang Zhang <yang.zhang.wz@gmail.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

arch/x86/kvm/vmx.c

@@ -927,6 +927,8 @@ static unsigned long *vmx_msr_bitmap_legacy;
 static unsigned long *vmx_msr_bitmap_longmode;
 static unsigned long *vmx_msr_bitmap_legacy_x2apic;
 static unsigned long *vmx_msr_bitmap_longmode_x2apic;
+static unsigned long *vmx_msr_bitmap_legacy_x2apic_apicv_inactive;
+static unsigned long *vmx_msr_bitmap_longmode_x2apic_apicv_inactive;
 static unsigned long *vmx_vmread_bitmap;
 static unsigned long *vmx_vmwrite_bitmap;
 
@@ -2524,10 +2526,17 @@ static void vmx_set_msr_bitmap(struct kvm_vcpu *vcpu)
 	else if (cpu_has_secondary_exec_ctrls() &&
 		 (vmcs_read32(SECONDARY_VM_EXEC_CONTROL) &
 		  SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE)) {
-		if (is_long_mode(vcpu))
-			msr_bitmap = vmx_msr_bitmap_longmode_x2apic;
-		else
-			msr_bitmap = vmx_msr_bitmap_legacy_x2apic;
+		if (enable_apicv && kvm_vcpu_apicv_active(vcpu)) {
+			if (is_long_mode(vcpu))
+				msr_bitmap = vmx_msr_bitmap_longmode_x2apic;
+			else
+				msr_bitmap = vmx_msr_bitmap_legacy_x2apic;
+		} else {
+			if (is_long_mode(vcpu))
+				msr_bitmap = vmx_msr_bitmap_longmode_x2apic_apicv_inactive;
+			else
+				msr_bitmap = vmx_msr_bitmap_legacy_x2apic_apicv_inactive;
+		}
 	} else {
 		if (is_long_mode(vcpu))
 			msr_bitmap = vmx_msr_bitmap_longmode;
@@ -4682,28 +4691,49 @@ static void vmx_disable_intercept_for_msr(u32 msr, bool longmode_only)
 						msr, MSR_TYPE_R | MSR_TYPE_W);
 }
 
-static void vmx_enable_intercept_msr_read_x2apic(u32 msr)
+static void vmx_enable_intercept_msr_read_x2apic(u32 msr, bool apicv_active)
 {
-	__vmx_enable_intercept_for_msr(vmx_msr_bitmap_legacy_x2apic,
-			msr, MSR_TYPE_R);
-	__vmx_enable_intercept_for_msr(vmx_msr_bitmap_longmode_x2apic,
-			msr, MSR_TYPE_R);
+	if (apicv_active) {
+		__vmx_enable_intercept_for_msr(vmx_msr_bitmap_legacy_x2apic,
+				msr, MSR_TYPE_R);
+		__vmx_enable_intercept_for_msr(vmx_msr_bitmap_longmode_x2apic,
+				msr, MSR_TYPE_R);
+	} else {
+		__vmx_enable_intercept_for_msr(vmx_msr_bitmap_legacy_x2apic_apicv_inactive,
+				msr, MSR_TYPE_R);
+		__vmx_enable_intercept_for_msr(vmx_msr_bitmap_longmode_x2apic_apicv_inactive,
+				msr, MSR_TYPE_R);
+	}
 }
 
-static void vmx_disable_intercept_msr_read_x2apic(u32 msr)
+static void vmx_disable_intercept_msr_read_x2apic(u32 msr, bool apicv_active)
 {
-	__vmx_disable_intercept_for_msr(vmx_msr_bitmap_legacy_x2apic,
-			msr, MSR_TYPE_R);
-	__vmx_disable_intercept_for_msr(vmx_msr_bitmap_longmode_x2apic,
-			msr, MSR_TYPE_R);
+	if (apicv_active) {
+		__vmx_disable_intercept_for_msr(vmx_msr_bitmap_legacy_x2apic,
+				msr, MSR_TYPE_R);
+		__vmx_disable_intercept_for_msr(vmx_msr_bitmap_longmode_x2apic,
+				msr, MSR_TYPE_R);
+	} else {
+		__vmx_disable_intercept_for_msr(vmx_msr_bitmap_legacy_x2apic_apicv_inactive,
+				msr, MSR_TYPE_R);
+		__vmx_disable_intercept_for_msr(vmx_msr_bitmap_longmode_x2apic_apicv_inactive,
+				msr, MSR_TYPE_R);
+	}
 }
 
-static void vmx_disable_intercept_msr_write_x2apic(u32 msr)
+static void vmx_disable_intercept_msr_write_x2apic(u32 msr, bool apicv_active)
 {
-	__vmx_disable_intercept_for_msr(vmx_msr_bitmap_legacy_x2apic,
-			msr, MSR_TYPE_W);
-	__vmx_disable_intercept_for_msr(vmx_msr_bitmap_longmode_x2apic,
-			msr, MSR_TYPE_W);
+	if (apicv_active) {
+		__vmx_disable_intercept_for_msr(vmx_msr_bitmap_legacy_x2apic,
+				msr, MSR_TYPE_W);
+		__vmx_disable_intercept_for_msr(vmx_msr_bitmap_longmode_x2apic,
+				msr, MSR_TYPE_W);
+	} else {
+		__vmx_disable_intercept_for_msr(vmx_msr_bitmap_legacy_x2apic_apicv_inactive,
+				msr, MSR_TYPE_W);
+		__vmx_disable_intercept_for_msr(vmx_msr_bitmap_longmode_x2apic_apicv_inactive,
+				msr, MSR_TYPE_W);
+	}
 }
 
 static bool vmx_get_enable_apicv(void)
@@ -6364,22 +6394,32 @@ static __init int hardware_setup(void)
 	if (!vmx_msr_bitmap_legacy_x2apic)
 		goto out2;
 
+	vmx_msr_bitmap_legacy_x2apic_apicv_inactive =
+				(unsigned long *)__get_free_page(GFP_KERNEL);
+	if (!vmx_msr_bitmap_legacy_x2apic_apicv_inactive)
+		goto out3;
+
 	vmx_msr_bitmap_longmode = (unsigned long *)__get_free_page(GFP_KERNEL);
 	if (!vmx_msr_bitmap_longmode)
-		goto out3;
+		goto out4;
 
 	vmx_msr_bitmap_longmode_x2apic =
 				(unsigned long *)__get_free_page(GFP_KERNEL);
 	if (!vmx_msr_bitmap_longmode_x2apic)
-		goto out4;
+		goto out5;
+
+	vmx_msr_bitmap_longmode_x2apic_apicv_inactive =
+				(unsigned long *)__get_free_page(GFP_KERNEL);
+	if (!vmx_msr_bitmap_longmode_x2apic_apicv_inactive)
+		goto out6;
 
 	vmx_vmread_bitmap = (unsigned long *)__get_free_page(GFP_KERNEL);
 	if (!vmx_vmread_bitmap)
-		goto out6;
+		goto out7;
 
 	vmx_vmwrite_bitmap = (unsigned long *)__get_free_page(GFP_KERNEL);
 	if (!vmx_vmwrite_bitmap)
-		goto out7;
+		goto out8;
 
 	memset(vmx_vmread_bitmap, 0xff, PAGE_SIZE);
 	memset(vmx_vmwrite_bitmap, 0xff, PAGE_SIZE);
@@ -6398,7 +6438,7 @@ static __init int hardware_setup(void)
 
 	if (setup_vmcs_config(&vmcs_config) < 0) {
 		r = -EIO;
-		goto out8;
+		goto out9;
 	}
 
 	if (boot_cpu_has(X86_FEATURE_NX))
@@ -6465,20 +6505,35 @@ static __init int hardware_setup(void)
 			vmx_msr_bitmap_legacy, PAGE_SIZE);
 	memcpy(vmx_msr_bitmap_longmode_x2apic,
 			vmx_msr_bitmap_longmode, PAGE_SIZE);
+	memcpy(vmx_msr_bitmap_legacy_x2apic_apicv_inactive,
+			vmx_msr_bitmap_legacy, PAGE_SIZE);
+	memcpy(vmx_msr_bitmap_longmode_x2apic_apicv_inactive,
+			vmx_msr_bitmap_longmode, PAGE_SIZE);
 
 	set_bit(0, vmx_vpid_bitmap); /* 0 is reserved for host */
 
+	/*
+	 * enable_apicv && kvm_vcpu_apicv_active()
+	 */
 	for (msr = 0x800; msr <= 0x8ff; msr++)
-		vmx_disable_intercept_msr_read_x2apic(msr);
+		vmx_disable_intercept_msr_read_x2apic(msr, true);
 
 	/* TMCCT */
-	vmx_enable_intercept_msr_read_x2apic(0x839);
+	vmx_enable_intercept_msr_read_x2apic(0x839, true);
 	/* TPR */
-	vmx_disable_intercept_msr_write_x2apic(0x808);
+	vmx_disable_intercept_msr_write_x2apic(0x808, true);
 	/* EOI */
-	vmx_disable_intercept_msr_write_x2apic(0x80b);
+	vmx_disable_intercept_msr_write_x2apic(0x80b, true);
 	/* SELF-IPI */
-	vmx_disable_intercept_msr_write_x2apic(0x83f);
+	vmx_disable_intercept_msr_write_x2apic(0x83f, true);
+
+	/*
+	 * (enable_apicv && !kvm_vcpu_apicv_active()) ||
+	 * 	!enable_apicv
+	 */
+	/* TPR */
+	vmx_disable_intercept_msr_read_x2apic(0x808, false);
+	vmx_disable_intercept_msr_write_x2apic(0x808, false);
 
 	if (enable_ept) {
 		kvm_mmu_set_mask_ptes(VMX_EPT_READABLE_MASK,
@@ -6525,14 +6580,18 @@ static __init int hardware_setup(void)
 
 	return alloc_kvm_area();
 
-out8:
+out9:
 	free_page((unsigned long)vmx_vmwrite_bitmap);
-out7:
+out8:
 	free_page((unsigned long)vmx_vmread_bitmap);
+out7:
+	free_page((unsigned long)vmx_msr_bitmap_longmode_x2apic_apicv_inactive);
 out6:
 	free_page((unsigned long)vmx_msr_bitmap_longmode_x2apic);
-out4:
+out5:
 	free_page((unsigned long)vmx_msr_bitmap_longmode);
+out4:
+	free_page((unsigned long)vmx_msr_bitmap_legacy_x2apic_apicv_inactive);
 out3:
 	free_page((unsigned long)vmx_msr_bitmap_legacy_x2apic);
 out2:
@@ -6548,7 +6607,9 @@ out:
 static __exit void hardware_unsetup(void)
 {
 	free_page((unsigned long)vmx_msr_bitmap_legacy_x2apic);
+	free_page((unsigned long)vmx_msr_bitmap_legacy_x2apic_apicv_inactive);
 	free_page((unsigned long)vmx_msr_bitmap_longmode_x2apic);
+	free_page((unsigned long)vmx_msr_bitmap_longmode_x2apic_apicv_inactive);
 	free_page((unsigned long)vmx_msr_bitmap_legacy);
 	free_page((unsigned long)vmx_msr_bitmap_longmode);
 	free_page((unsigned long)vmx_io_bitmap_b);
@@ -8439,12 +8500,7 @@ static void vmx_set_virtual_x2apic_mode(struct kvm_vcpu *vcpu, bool set)
 		return;
 	}
 
-	/*
-	 * There is not point to enable virtualize x2apic without enable
-	 * apicv
-	 */
-	if (!cpu_has_vmx_virtualize_x2apic_mode() ||
-				!kvm_vcpu_apicv_active(vcpu))
+	if (!cpu_has_vmx_virtualize_x2apic_mode())
 		return;
 
 	if (!cpu_need_tpr_shadow(vcpu))