linux-kernel - [PATCH 13/32] KVM: nVMX: Handle virtual timer vector VMCS field

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Message-ID: <cde898b77379481886f7abb2b78dd32bba0b2ba1.1770116051.git.isaku.yamahata@intel.com>
Date: Tue,  3 Feb 2026 10:16:56 -0800
From: isaku.yamahata@...el.com
To: kvm@...r.kernel.org
Cc: isaku.yamahata@...el.com,
	isaku.yamahata@...il.com,
	Paolo Bonzini <pbonzini@...hat.com>,
	Sean Christopherson <seanjc@...gle.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 13/32] KVM: nVMX: Handle virtual timer vector VMCS field

From: Isaku Yamahata <isaku.yamahata@...el.com>

Support virtual timer vector VMCS field.
Opportunistically add a size check of struct vmcs12.

Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
---
 arch/x86/kvm/vmx/nested.c             | 15 ++++++++++++++-
 arch/x86/kvm/vmx/vmcs12.c             |  3 +++
 arch/x86/kvm/vmx/vmcs12.h             |  2 ++
 arch/x86/kvm/vmx/vmcs_shadow_fields.h |  1 +
 4 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 191317479d5e..5829562145a7 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -86,6 +86,15 @@ static void init_vmcs_shadow_fields(void)
 			pr_err("Missing field from shadow_read_only_field %x\n",
 			       field + 1);
 
+		switch (field) {
+		case GUEST_APIC_TIMER_VECTOR:
+			if (!cpu_has_vmx_apic_timer_virt())
+				continue;
+			break;
+		default:
+			break;
+		}
+
 		clear_bit(field, vmx_vmread_bitmap);
 		if (field & 1)
 #ifdef CONFIG_X86_64
@@ -2539,7 +2548,8 @@ static void prepare_vmcs02_early(struct vcpu_vmx *vmx, struct loaded_vmcs *vmcs0
 	if (cpu_has_tertiary_exec_ctrls()) {
 		u64 ctls = 0;
 
-		/* guest apic timer virtualization will come */
+		if (nested_cpu_has_guest_apic_timer(vmcs12))
+			ctls |= TERTIARY_EXEC_GUEST_APIC_TIMER;
 
 		tertiary_exec_controls_set(vmx, ctls);
 	}
@@ -2733,6 +2743,9 @@ static void prepare_vmcs02_rare(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12)
 		vmcs_write64(EOI_EXIT_BITMAP3, vmcs12->eoi_exit_bitmap3);
 	}
 
+	if (nested_cpu_has_guest_apic_timer(vmcs12))
+		vmcs_write16(GUEST_APIC_TIMER_VECTOR, vmcs12->virtual_timer_vector);
+
 	/*
 	 * Make sure the msr_autostore list is up to date before we set the
 	 * count in the vmcs02.
diff --git a/arch/x86/kvm/vmx/vmcs12.c b/arch/x86/kvm/vmx/vmcs12.c
index 2a21864a020a..3842ee1ddabf 100644
--- a/arch/x86/kvm/vmx/vmcs12.c
+++ b/arch/x86/kvm/vmx/vmcs12.c
@@ -3,6 +3,8 @@
 
 #include "vmcs12.h"
 
+static_assert(sizeof(struct vmcs12) <= VMCS12_SIZE);
+
 #define VMCS12_OFFSET(x) offsetof(struct vmcs12, x)
 #define FIELD(number, name)	[ROL16(number, 6)] = VMCS12_OFFSET(name)
 #define FIELD64(number, name)						\
@@ -22,6 +24,7 @@ const unsigned short vmcs12_field_offsets[] = {
 	FIELD(GUEST_TR_SELECTOR, guest_tr_selector),
 	FIELD(GUEST_INTR_STATUS, guest_intr_status),
 	FIELD(GUEST_PML_INDEX, guest_pml_index),
+	FIELD(GUEST_APIC_TIMER_VECTOR, virtual_timer_vector),
 	FIELD(HOST_ES_SELECTOR, host_es_selector),
 	FIELD(HOST_CS_SELECTOR, host_cs_selector),
 	FIELD(HOST_SS_SELECTOR, host_ss_selector),
diff --git a/arch/x86/kvm/vmx/vmcs12.h b/arch/x86/kvm/vmx/vmcs12.h
index db1f86a48343..d8e09de44f2a 100644
--- a/arch/x86/kvm/vmx/vmcs12.h
+++ b/arch/x86/kvm/vmx/vmcs12.h
@@ -191,6 +191,7 @@ struct __packed vmcs12 {
 	u16 host_gs_selector;
 	u16 host_tr_selector;
 	u16 guest_pml_index;
+	u16 virtual_timer_vector;
 };
 
 /*
@@ -373,6 +374,7 @@ static inline void vmx_check_vmcs12_offsets(void)
 	CHECK_OFFSET(host_gs_selector, 992);
 	CHECK_OFFSET(host_tr_selector, 994);
 	CHECK_OFFSET(guest_pml_index, 996);
+	CHECK_OFFSET(virtual_timer_vector, 998);
 }
 
 extern const unsigned short vmcs12_field_offsets[];
diff --git a/arch/x86/kvm/vmx/vmcs_shadow_fields.h b/arch/x86/kvm/vmx/vmcs_shadow_fields.h
index cad128d1657b..db1558d11c4c 100644
--- a/arch/x86/kvm/vmx/vmcs_shadow_fields.h
+++ b/arch/x86/kvm/vmx/vmcs_shadow_fields.h
@@ -34,6 +34,7 @@ BUILD_BUG_ON(1)
 /* 16-bits */
 SHADOW_FIELD_RW(GUEST_INTR_STATUS, guest_intr_status)
 SHADOW_FIELD_RW(GUEST_PML_INDEX, guest_pml_index)
+SHADOW_FIELD_RO(GUEST_APIC_TIMER_VECTOR, virtual_timer_vector)
 SHADOW_FIELD_RW(HOST_FS_SELECTOR, host_fs_selector)
 SHADOW_FIELD_RW(HOST_GS_SELECTOR, host_gs_selector)
 
-- 
2.45.2