1 files changed, 76 insertions, 53 deletions

diff --git a/arch/loongarch/kvm/timer.c b/arch/loongarch/kvm/timer.c
index 284bf553fefe..111328f60872 100644
--- a/arch/loongarch/kvm/timer.c
+++ b/arch/loongarch/kvm/timer.c
@@ -65,40 +65,23 @@ void kvm_init_timer(struct kvm_vcpu *vcpu, unsigned long timer_hz)
 }
 
 /*
- * Restore hard timer state and enable guest to access timer registers
- * without trap, should be called with irq disabled
- */
-void kvm_acquire_timer(struct kvm_vcpu *vcpu)
-{
-	unsigned long cfg;
-
-	cfg = read_csr_gcfg();
-	if (!(cfg & CSR_GCFG_TIT))
-		return;
-
-	/* Enable guest access to hard timer */
-	write_csr_gcfg(cfg & ~CSR_GCFG_TIT);
-
-	/*
-	 * Freeze the soft-timer and sync the guest stable timer with it. We do
-	 * this with interrupts disabled to avoid latency.
-	 */
-	hrtimer_cancel(&vcpu->arch.swtimer);
-}
-
-/*
  * Restore soft timer state from saved context.
  */
 void kvm_restore_timer(struct kvm_vcpu *vcpu)
 {
-	unsigned long cfg, delta, period;
+	unsigned long cfg, estat;
+	unsigned long ticks, delta, period;
 	ktime_t expire, now;
 	struct loongarch_csrs *csr = vcpu->arch.csr;
 
 	/*
 	 * Set guest stable timer cfg csr
+	 * Disable timer before restore estat CSR register, avoid to
+	 * get invalid timer interrupt for old timer cfg
 	 */
 	cfg = kvm_read_sw_gcsr(csr, LOONGARCH_CSR_TCFG);
+
+	write_gcsr_timercfg(0);
 	kvm_restore_hw_gcsr(csr, LOONGARCH_CSR_ESTAT);
 	kvm_restore_hw_gcsr(csr, LOONGARCH_CSR_TCFG);
 	if (!(cfg & CSR_TCFG_EN)) {
@@ -108,23 +91,55 @@ void kvm_restore_timer(struct kvm_vcpu *vcpu)
 	}
 
 	/*
+	 * Freeze the soft-timer and sync the guest stable timer with it.
+	 */
+	hrtimer_cancel(&vcpu->arch.swtimer);
+
+	/*
+	 * From LoongArch Reference Manual Volume 1 Chapter 7.6.2
+	 * If oneshot timer is fired, CSR TVAL will be -1, there are two
+	 * conditions:
+	 *  1) timer is fired during exiting to host
+	 *  2) timer is fired and vm is doing timer irq, and then exiting to
+	 *     host. Host should not inject timer irq to avoid spurious
+	 *     timer interrupt again
+	 */
+	ticks = kvm_read_sw_gcsr(csr, LOONGARCH_CSR_TVAL);
+	estat = kvm_read_sw_gcsr(csr, LOONGARCH_CSR_ESTAT);
+	if (!(cfg & CSR_TCFG_PERIOD) && (ticks > cfg)) {
+		/*
+		 * Writing 0 to LOONGARCH_CSR_TVAL will inject timer irq
+		 * and set CSR TVAL with -1
+		 */
+		write_gcsr_timertick(0);
+
+		/*
+		 * Writing CSR_TINTCLR_TI to LOONGARCH_CSR_TINTCLR will clear
+		 * timer interrupt, and CSR TVAL keeps unchanged with -1, it
+		 * avoids spurious timer interrupt
+		 */
+		if (!(estat & CPU_TIMER))
+			gcsr_write(CSR_TINTCLR_TI, LOONGARCH_CSR_TINTCLR);
+		return;
+	}
+
+	/*
 	 * Set remainder tick value if not expired
 	 */
+	delta = 0;
 	now = ktime_get();
 	expire = vcpu->arch.expire;
 	if (ktime_before(now, expire))
 		delta = ktime_to_tick(vcpu, ktime_sub(expire, now));
-	else {
-		if (cfg & CSR_TCFG_PERIOD) {
-			period = cfg & CSR_TCFG_VAL;
-			delta = ktime_to_tick(vcpu, ktime_sub(now, expire));
-			delta = period - (delta % period);
-		} else
-			delta = 0;
+	else if (cfg & CSR_TCFG_PERIOD) {
+		period = cfg & CSR_TCFG_VAL;
+		delta = ktime_to_tick(vcpu, ktime_sub(now, expire));
+		delta = period - (delta % period);
+
 		/*
 		 * Inject timer here though sw timer should inject timer
 		 * interrupt async already, since sw timer may be cancelled
-		 * during injecting intr async in function kvm_acquire_timer
+		 * during injecting intr async
 		 */
 		kvm_queue_irq(vcpu, INT_TI);
 	}
@@ -139,27 +154,41 @@ void kvm_restore_timer(struct kvm_vcpu *vcpu)
  */
 static void _kvm_save_timer(struct kvm_vcpu *vcpu)
 {
-	unsigned long ticks, delta;
+	unsigned long ticks, delta, cfg;
 	ktime_t expire;
 	struct loongarch_csrs *csr = vcpu->arch.csr;
 
+	cfg = kvm_read_sw_gcsr(csr, LOONGARCH_CSR_TCFG);
 	ticks = kvm_read_sw_gcsr(csr, LOONGARCH_CSR_TVAL);
-	delta = tick_to_ns(vcpu, ticks);
-	expire = ktime_add_ns(ktime_get(), delta);
-	vcpu->arch.expire = expire;
-	if (ticks) {
+
+	/*
+	 * From LoongArch Reference Manual Volume 1 Chapter 7.6.2
+	 * If period timer is fired, CSR TVAL will be reloaded from CSR TCFG
+	 * If oneshot timer is fired, CSR TVAL will be -1
+	 * Here judge one-shot timer fired by checking whether TVAL is larger
+	 * than TCFG
+	 */
+	if (ticks < cfg) {
+		delta = tick_to_ns(vcpu, ticks);
+		expire = ktime_add_ns(ktime_get(), delta);
+		vcpu->arch.expire = expire;
+
 		/*
-		 * Update hrtimer to use new timeout
 		 * HRTIMER_MODE_PINNED is suggested since vcpu may run in
 		 * the same physical cpu in next time
 		 */
-		hrtimer_cancel(&vcpu->arch.swtimer);
 		hrtimer_start(&vcpu->arch.swtimer, expire, HRTIMER_MODE_ABS_PINNED);
-	} else
+	} else if (vcpu->stat.generic.blocking) {
 		/*
-		 * Inject timer interrupt so that hall polling can dectect and exit
+		 * Inject timer interrupt so that halt polling can dectect and exit.
+		 * VCPU is scheduled out already and sleeps in rcuwait queue and
+		 * will not poll pending events again. kvm_queue_irq() is not enough,
+		 * hrtimer swtimer should be used here.
 		 */
-		kvm_queue_irq(vcpu, INT_TI);
+		expire = ktime_add_ns(ktime_get(), 10);
+		vcpu->arch.expire = expire;
+		hrtimer_start(&vcpu->arch.swtimer, expire, HRTIMER_MODE_ABS_PINNED);
+	}
 }
 
 /*
@@ -168,21 +197,15 @@ static void _kvm_save_timer(struct kvm_vcpu *vcpu)
  */
 void kvm_save_timer(struct kvm_vcpu *vcpu)
 {
-	unsigned long cfg;
 	struct loongarch_csrs *csr = vcpu->arch.csr;
 
 	preempt_disable();
-	cfg = read_csr_gcfg();
-	if (!(cfg & CSR_GCFG_TIT)) {
-		/* Disable guest use of hard timer */
-		write_csr_gcfg(cfg | CSR_GCFG_TIT);
-
-		/* Save hard timer state */
-		kvm_save_hw_gcsr(csr, LOONGARCH_CSR_TCFG);
-		kvm_save_hw_gcsr(csr, LOONGARCH_CSR_TVAL);
-		if (kvm_read_sw_gcsr(csr, LOONGARCH_CSR_TCFG) & CSR_TCFG_EN)
-			_kvm_save_timer(vcpu);
-	}
+
+	/* Save hard timer state */
+	kvm_save_hw_gcsr(csr, LOONGARCH_CSR_TCFG);
+	kvm_save_hw_gcsr(csr, LOONGARCH_CSR_TVAL);
+	if (kvm_read_sw_gcsr(csr, LOONGARCH_CSR_TCFG) & CSR_TCFG_EN)
+		_kvm_save_timer(vcpu);
 
 	/* Save timer-related state to vCPU context */
 	kvm_save_hw_gcsr(csr, LOONGARCH_CSR_ESTAT);