[RFC v4 10/10] KVM: arm/arm64: Emulate the EL1 phys timer registers

[Jintack Lim]

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@xxxxxxxxxxxxxxx>
Reviewed-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
---
 arch/arm64/kvm/sys_regs.c    | 37 ++++++++++++++++++++++++++++++++++---
 include/kvm/arm_arch_timer.h |  2 ++
 virt/kvm/arm/arch_timer.c    |  2 +-
 3 files changed, 37 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 1cd3464..0e26f8c 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/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;
 }
 
diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h
index f1d2fba0..fe797d6 100644
--- a/include/kvm/arm_arch_timer.h
+++ b/include/kvm/arm_arch_timer.h
@@ -72,6 +72,8 @@ int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu,
 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);
diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index 33257b5..35d7100 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/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);
 }
-- 
1.9.1