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Subject[RFC 8/8] KVM: arm/arm64: Emulate the EL1 phys timer register access
Date
Emulate read and write operations to CNTP_TVAL, CNTP_CVAL and CNTP_CTL.
Now the VM is able to use the EL1 physical timer.

Signed-off-by: Jintack Lim <jintack@cs.columbia.edu>
---
arch/arm64/kvm/sys_regs.c | 35 ++++++++++++++++++++++++++++++++---
include/kvm/arm_arch_timer.h | 3 +++
virt/kvm/arm/arch_timer.c | 4 ++--
3 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index fd9e747..7cef94f 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -824,7 +824,15 @@ 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);
+ cycle_t now = kvm_phys_timer_read();
+
+ if (p->is_write) {
+ ptimer->cnt_cval = p->regval + now;
+ kvm_timer_emulate(vcpu, ptimer);
+ } else
+ p->regval = ptimer->cnt_cval - now;
+
return true;
}

@@ -832,7 +840,21 @@ 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;
+ kvm_timer_emulate(vcpu, ptimer);
+ } else {
+ cycle_t now = kvm_phys_timer_read();
+
+ p->regval = ptimer->cnt_ctl;
+ /* Set ISTATUS bit if it's expired */
+ if (ptimer->cnt_cval <= now)
+ p->regval |= ARCH_TIMER_CTRL_IT_STAT;
+ }
+
return true;
}

@@ -840,7 +862,14 @@ 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;
+ kvm_timer_emulate(vcpu, ptimer);
+ } 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 04ed9c1..776579b 100644
--- a/include/kvm/arm_arch_timer.h
+++ b/include/kvm/arm_arch_timer.h
@@ -75,6 +75,9 @@ bool kvm_timer_should_fire(struct kvm_vcpu *vcpu,
struct arch_timer_context *timer_ctx);
void kvm_timer_schedule(struct kvm_vcpu *vcpu);
void kvm_timer_unschedule(struct kvm_vcpu *vcpu);
+void kvm_timer_emulate(struct kvm_vcpu *vcpu, struct arch_timer_context *timer);
+
+cycle_t kvm_phys_timer_read(void);

void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu);

diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index be8d953..7a161f8 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -39,7 +39,7 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu)
vcpu_vtimer(vcpu)->active_cleared_last = false;
}

-static cycle_t kvm_phys_timer_read(void)
+cycle_t kvm_phys_timer_read(void)
{
return timecounter->cc->read(timecounter->cc);
}
@@ -258,7 +258,7 @@ static int kvm_timer_update_state(struct kvm_vcpu *vcpu)
* Schedule the background timer for the emulated timer. The background timer
* runs whenever vcpu is runnable and the timer is not expired.
*/
-static void kvm_timer_emulate(struct kvm_vcpu *vcpu,
+void kvm_timer_emulate(struct kvm_vcpu *vcpu,
struct arch_timer_context *timer_ctx)
{
struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
--
1.9.1

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