KVM: arm/arm64: Use kvm_arm_timer_set/get_reg for guest register traps

When trapping on a guest access to one of the timer registers, we were
messing with the internals of the timer state from the sysregs handling
code, and that logic was about to receive more added complexity when
optimizing the timer handling code.

Therefore, since we already have timer register access functions (to
access registers from userspace), reuse those for the timer register
traps from a VM and let the timer code maintain its own consistency.

Signed-off-by: Christoffer Dall <cdall@linaro.org>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>

arch/arm64/kvm/sys_regs.c

@@ -841,13 +841,16 @@ static bool access_cntp_tval(struct kvm_vcpu *vcpu,
 		struct sys_reg_params *p,
 		const struct sys_reg_desc *r)
 {
-	struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
 	u64 now = kvm_phys_timer_read();
+	u64 cval;
 
-	if (p->is_write)
-		ptimer->cnt_cval = p->regval + now;
-	else
-		p->regval = ptimer->cnt_cval - now;
+	if (p->is_write) {
+		kvm_arm_timer_set_reg(vcpu, KVM_REG_ARM_PTIMER_CVAL,
+				      p->regval + now);
+	} else {
+		cval = kvm_arm_timer_get_reg(vcpu, KVM_REG_ARM_PTIMER_CVAL);
+		p->regval = cval - now;
+	}
 
 	return true;
 }
@@ -856,24 +859,10 @@ static bool access_cntp_ctl(struct kvm_vcpu *vcpu,
 		struct sys_reg_params *p,
 		const struct sys_reg_desc *r)
 {
-	struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
-
-	if (p->is_write) {
-		/* ISTATUS bit is read-only */
-		ptimer->cnt_ctl = p->regval & ~ARCH_TIMER_CTRL_IT_STAT;
-	} else {
-		u64 now = kvm_phys_timer_read();
-
-		p->regval = ptimer->cnt_ctl;
-		/*
-		 * Set ISTATUS bit if it's expired.
-		 * Note that according to ARMv8 ARM Issue A.k, ISTATUS bit is
-		 * UNKNOWN when ENABLE bit is 0, so we chose to set ISTATUS bit
-		 * regardless of ENABLE bit for our implementation convenience.
-		 */
-		if (ptimer->cnt_cval <= now)
-			p->regval |= ARCH_TIMER_CTRL_IT_STAT;
-	}
+	if (p->is_write)
+		kvm_arm_timer_set_reg(vcpu, KVM_REG_ARM_PTIMER_CTL, p->regval);
+	else
+		p->regval = kvm_arm_timer_get_reg(vcpu, KVM_REG_ARM_PTIMER_CTL);
 
 	return true;
 }
@@ -882,12 +871,10 @@ static bool access_cntp_cval(struct kvm_vcpu *vcpu,
 		struct sys_reg_params *p,
 		const struct sys_reg_desc *r)
 {
-	struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
-
 	if (p->is_write)
-		ptimer->cnt_cval = p->regval;
+		kvm_arm_timer_set_reg(vcpu, KVM_REG_ARM_PTIMER_CVAL, p->regval);
 	else
-		p->regval = ptimer->cnt_cval;
+		p->regval = kvm_arm_timer_get_reg(vcpu, KVM_REG_ARM_PTIMER_CVAL);
 
 	return true;
 }