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Subject[RFC v3 10/10] KVM: arm/arm64: Emulate the EL1 phys timer registers
Date
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>
---
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 1806e5e..93c811c 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

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