LoongArch: KVM: Access mailbox directly in mail_send()

With function mail_send(), it is to write mailbox of other VCPUs.
Existing simple APIs read_mailbox()/write_mailbox() can be used directly
rather than send command on IOCSR address.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

Author: bibo-mao

arch/loongarch/kvm/intc/ipi.c

@@ -101,6 +101,34 @@ static void write_mailbox(struct kvm_vcpu *vcpu, int offset, uint64_t data, int
 	spin_unlock(&vcpu->arch.ipi_state.lock);
 }
 
+static int mail_send(struct kvm *kvm, uint64_t data)
+{
+	int i, cpu, mailbox, offset;
+	uint32_t val = 0, mask = 0;
+	struct kvm_vcpu *vcpu;
+
+	cpu = ((data & 0xffffffff) >> 16) & 0x3ff;
+	vcpu = kvm_get_vcpu_by_cpuid(kvm, cpu);
+	if (unlikely(vcpu == NULL)) {
+		kvm_err("%s: invalid target cpu: %d\n", __func__, cpu);
+		return -EINVAL;
+	}
+	mailbox = ((data & 0xffffffff) >> 2) & 0x7;
+	offset = IOCSR_IPI_BUF_20 + mailbox * 4;
+	if ((data >> 27) & 0xf) {
+		val = read_mailbox(vcpu, offset, 4);
+		for (i = 0; i < 4; i++)
+			if (data & (BIT(27 + i)))
+				mask |= (0xff << (i * 8));
+		val &= mask;
+	}
+
+	val |= ((uint32_t)(data >> 32) & ~mask);
+	write_mailbox(vcpu, offset, val, 4);
+
+	return 0;
+}
+
 static int send_ipi_data(struct kvm_vcpu *vcpu, gpa_t addr, uint64_t data)
 {
 	int i, idx, ret;
@@ -137,23 +165,6 @@ static int send_ipi_data(struct kvm_vcpu *vcpu, gpa_t addr, uint64_t data)
 	return ret;
 }
 
-static int mail_send(struct kvm *kvm, uint64_t data)
-{
-	int cpu, mailbox, offset;
-	struct kvm_vcpu *vcpu;
-
-	cpu = ((data & 0xffffffff) >> 16) & 0x3ff;
-	vcpu = kvm_get_vcpu_by_cpuid(kvm, cpu);
-	if (unlikely(vcpu == NULL)) {
-		kvm_err("%s: invalid target cpu: %d\n", __func__, cpu);
-		return -EINVAL;
-	}
-	mailbox = ((data & 0xffffffff) >> 2) & 0x7;
-	offset = IOCSR_IPI_BASE + IOCSR_IPI_BUF_20 + mailbox * 4;
-
-	return send_ipi_data(vcpu, offset, data);
-}
-
 static int any_send(struct kvm *kvm, uint64_t data)
 {
 	int cpu, offset;