KVM: arm/arm64: Emulate the EL1 phys timer registers

Emulate read and write operations to CNTP_TVAL, CNTP_CVAL and CNTP_CTL.
Now VMs are able to use the EL1 physical timer.
Signed-off-by: Jintack Lim <jintack@cs.columbia.edu>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

arch/arm64/kvm/sys_regs.c

@@ -824,7 +824,14 @@ static bool access_cntp_tval(struct kvm_vcpu *vcpu,
 		struct sys_reg_params *p,
 		const struct sys_reg_desc *r)
 {
-	kvm_inject_undefined(vcpu);
+	struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
+	u64 now = kvm_phys_timer_read();
+
+	if (p->is_write)
+		ptimer->cnt_cval = p->regval + now;
+	else
+		p->regval = ptimer->cnt_cval - now;
+
 	return true;
 }
 
@@ -832,7 +839,25 @@ static bool access_cntp_ctl(struct kvm_vcpu *vcpu,
 		struct sys_reg_params *p,
 		const struct sys_reg_desc *r)
 {
-	kvm_inject_undefined(vcpu);
+	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;
+	}
+
 	return true;
 }
 
@@ -840,7 +865,13 @@ static bool access_cntp_cval(struct kvm_vcpu *vcpu,
 		struct sys_reg_params *p,
 		const struct sys_reg_desc *r)
 {
-	kvm_inject_undefined(vcpu);
+	struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
+
+	if (p->is_write)
+		ptimer->cnt_cval = p->regval;
+	else
+		p->regval = ptimer->cnt_cval;
+
 	return true;
 }
 

include/kvm/arm_arch_timer.h

@@ -72,6 +72,8 @@ bool kvm_timer_should_fire(struct arch_timer_context *timer_ctx);
 void kvm_timer_schedule(struct kvm_vcpu *vcpu);
 void kvm_timer_unschedule(struct kvm_vcpu *vcpu);
 
+u64 kvm_phys_timer_read(void);
+
 void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu);
 
 void kvm_timer_init_vhe(void);

virt/kvm/arm/arch_timer.c

@@ -40,7 +40,7 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu)
 	vcpu_vtimer(vcpu)->active_cleared_last = false;
 }
 
-static u64 kvm_phys_timer_read(void)
+u64 kvm_phys_timer_read(void)
 {
 	return timecounter->cc->read(timecounter->cc);
 }