LoongArch: KVM: Fix HW timer interrupt lost when inject interrupt by software

commit 2433f3f upstream.

With passthrough HW timer, timer interrupt is injected by HW. When
inject emulated CPU interrupt by software such SIP0/SIP1/IPI, HW timer
interrupt may be lost.

Here check whether there is timer tick value inversion before and after
injecting emulated CPU interrupt by software, timer enabling by reading
timer cfg register is skipped. If the timer tick value is detected with
changing, then timer should be enabled. And inject a timer interrupt by
software if there is.

Cc: <stable@vger.kernel.org>
Fixes: f45ad5b ("LoongArch: KVM: Implement vcpu interrupt operations").
Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: bibo-mao

arch/loongarch/kvm/interrupt.c

@@ -27,6 +27,7 @@ static unsigned int priority_to_irq[EXCCODE_INT_NUM] = {
 static int kvm_irq_deliver(struct kvm_vcpu *vcpu, unsigned int priority)
 {
 	unsigned int irq = 0;
+	unsigned long old, new;
 
 	clear_bit(priority, &vcpu->arch.irq_pending);
 	if (priority < EXCCODE_INT_NUM)
@@ -42,7 +43,13 @@ static int kvm_irq_deliver(struct kvm_vcpu *vcpu, unsigned int priority)
 	case INT_IPI:
 	case INT_SWI0:
 	case INT_SWI1:
+		old = kvm_read_hw_gcsr(LOONGARCH_CSR_TVAL);
 		set_gcsr_estat(irq);
+		new = kvm_read_hw_gcsr(LOONGARCH_CSR_TVAL);
+
+		/* Inject TI if TVAL inverted */
+		if (new > old)
+			set_gcsr_estat(CPU_TIMER);
 		break;
 
 	case INT_HWI0 ... INT_HWI7:
@@ -59,6 +66,7 @@ static int kvm_irq_deliver(struct kvm_vcpu *vcpu, unsigned int priority)
 static int kvm_irq_clear(struct kvm_vcpu *vcpu, unsigned int priority)
 {
 	unsigned int irq = 0;
+	unsigned long old, new;
 
 	clear_bit(priority, &vcpu->arch.irq_clear);
 	if (priority < EXCCODE_INT_NUM)
@@ -74,7 +82,13 @@ static int kvm_irq_clear(struct kvm_vcpu *vcpu, unsigned int priority)
 	case INT_IPI:
 	case INT_SWI0:
 	case INT_SWI1:
+		old = kvm_read_hw_gcsr(LOONGARCH_CSR_TVAL);
 		clear_gcsr_estat(irq);
+		new = kvm_read_hw_gcsr(LOONGARCH_CSR_TVAL);
+
+		/* Inject TI if TVAL inverted */
+		if (new > old)
+			set_gcsr_estat(CPU_TIMER);
 		break;
 
 	case INT_HWI0 ... INT_HWI7: