KVM: VMX: Move vt_apicv_pre_state_restore() to posted_intr.c and tweak name

In preparation for a cleanup of the kvm_x86_ops struct for TDX, all vt_*
functions are expected to act as glue functions that route to either tdx_*
or vmx_* based on the VM type. Specifically, the pattern is:

vt_abc:
    if (is_td())
        return tdx_abc();
    return vmx_abc();

But vt_apicv_pre_state_restore() does not follow this pattern. To
facilitate that cleanup, rename and move vt_apicv_pre_state_restore() into
posted_intr.c.

Opportunistically turn vcpu_to_pi_desc() back into a static function, as
the only reason it was exposed outside of posted_intr.c was for
vt_apicv_pre_state_restore().

No functional change intended.

Suggested-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/kvm/Z6v9yjWLNTU6X90d@google.com/
Cc: Sean Christopherson <seanjc@google.com>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linxu.intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
Link: https://lore.kernel.org/r/20250318-vverma7-cleanup_x86_ops-v2-2-701e82d6b779@intel.com
[sean: apply Chao's suggestions, massage shortlog]
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: stellarhopper

arch/x86/kvm/vmx/main.c

@@ -315,14 +315,6 @@ static void vt_set_virtual_apic_mode(struct kvm_vcpu *vcpu)
 	return vmx_set_virtual_apic_mode(vcpu);
 }
 
-static void vt_apicv_pre_state_restore(struct kvm_vcpu *vcpu)
-{
-	struct pi_desc *pi = vcpu_to_pi_desc(vcpu);
-
-	pi_clear_on(pi);
-	memset(pi->pir, 0, sizeof(pi->pir));
-}
-
 static void vt_hwapic_isr_update(struct kvm_vcpu *vcpu, int max_isr)
 {
 	if (is_td_vcpu(vcpu))
@@ -983,7 +975,7 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
 	.set_apic_access_page_addr = vt_set_apic_access_page_addr,
 	.refresh_apicv_exec_ctrl = vt_refresh_apicv_exec_ctrl,
 	.load_eoi_exitmap = vt_load_eoi_exitmap,
-	.apicv_pre_state_restore = vt_apicv_pre_state_restore,
+	.apicv_pre_state_restore = pi_apicv_pre_state_restore,
 	.required_apicv_inhibits = VMX_REQUIRED_APICV_INHIBITS,
 	.hwapic_isr_update = vt_hwapic_isr_update,
 	.sync_pir_to_irr = vt_sync_pir_to_irr,

arch/x86/kvm/vmx/posted_intr.c

@@ -34,7 +34,7 @@ static DEFINE_PER_CPU(raw_spinlock_t, wakeup_vcpus_on_cpu_lock);
 
 #define PI_LOCK_SCHED_OUT SINGLE_DEPTH_NESTING
 
-struct pi_desc *vcpu_to_pi_desc(struct kvm_vcpu *vcpu)
+static struct pi_desc *vcpu_to_pi_desc(struct kvm_vcpu *vcpu)
 {
 	return &(to_vt(vcpu)->pi_desc);
 }
@@ -264,6 +264,14 @@ void __init pi_init_cpu(int cpu)
 	raw_spin_lock_init(&per_cpu(wakeup_vcpus_on_cpu_lock, cpu));
 }
 
+void pi_apicv_pre_state_restore(struct kvm_vcpu *vcpu)
+{
+	struct pi_desc *pi = vcpu_to_pi_desc(vcpu);
+
+	pi_clear_on(pi);
+	memset(pi->pir, 0, sizeof(pi->pir));
+}
+
 bool pi_has_pending_interrupt(struct kvm_vcpu *vcpu)
 {
 	struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu);

arch/x86/kvm/vmx/posted_intr.h

@@ -5,12 +5,11 @@
 #include <linux/bitmap.h>
 #include <asm/posted_intr.h>
 
-struct pi_desc *vcpu_to_pi_desc(struct kvm_vcpu *vcpu);
-
 void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu);
 void vmx_vcpu_pi_put(struct kvm_vcpu *vcpu);
 void pi_wakeup_handler(void);
 void __init pi_init_cpu(int cpu);
+void pi_apicv_pre_state_restore(struct kvm_vcpu *vcpu);
 bool pi_has_pending_interrupt(struct kvm_vcpu *vcpu);
 int vmx_pi_update_irte(struct kvm *kvm, unsigned int host_irq,
 		       uint32_t guest_irq, bool set);