[PATCH] KVM: x86: Add a helper to handle 64-bit APIC writes to ICR

[Sean Christopherson]

Add a helper to handle 64-bit APIC writes, e.g. for x2APIC WRMSR, to
deduplicate the handling of ICR writes, which KVM needs to emulate as
back-to-back writes to ICR2 and then ICR.  Future support for IPI
virtualization will add yet another path where KVM must handle a 64-bit
APIC write.

Opportunistically fix the comment; ICR2 holds the destination (if there's
no shorthand), not the vector.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
 arch/x86/kvm/lapic.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 76fb00921203..5f526ee10301 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2183,6 +2183,14 @@ void kvm_lapic_set_eoi(struct kvm_vcpu *vcpu)
 }
 EXPORT_SYMBOL_GPL(kvm_lapic_set_eoi);

+static int kvm_lapic_reg_write64(struct kvm_lapic *apic, u32 reg, u64 data)
+{
+	/* For 64-bit ICR writes, set ICR2 (dest) before ICR (command). */
+	if (reg == APIC_ICR)
+		kvm_lapic_reg_write(apic, APIC_ICR2, (u32)(data >> 32));
+	return kvm_lapic_reg_write(apic, reg, (u32)data);
+}
+
 /* emulate APIC access in a trap manner */
 void kvm_apic_write_nodecode(struct kvm_vcpu *vcpu, u32 offset)
 {
@@ -2794,10 +2802,7 @@ int kvm_x2apic_msr_write(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 	if (reg == APIC_ICR2)
 		return 1;

-	/* if this is ICR write vector before command */
-	if (reg == APIC_ICR)
-		kvm_lapic_reg_write(apic, APIC_ICR2, (u32)(data >> 32));
-	return kvm_lapic_reg_write(apic, reg, (u32)data);
+	return kvm_lapic_reg_write64(apic, reg, data);
 }

 int kvm_x2apic_msr_read(struct kvm_vcpu *vcpu, u32 msr, u64 *data)
@@ -2828,10 +2833,7 @@ int kvm_hv_vapic_msr_write(struct kvm_vcpu *vcpu, u32 reg, u64 data)
 	if (!lapic_in_kernel(vcpu))
 		return 1;

-	/* if this is ICR write vector before command */
-	if (reg == APIC_ICR)
-		kvm_lapic_reg_write(apic, APIC_ICR2, (u32)(data >> 32));
-	return kvm_lapic_reg_write(apic, reg, (u32)data);
+	return kvm_lapic_reg_write64(apic, reg, data);
 }

 int kvm_hv_vapic_msr_read(struct kvm_vcpu *vcpu, u32 reg, u64 *data)
--