Re: [RFC PATCH 12/28] KVM: arm64: Support timers in realm RECs

Ganapatrao Kulkarni
2024-03-18T11:28:24Z

On 27-01-2023 04:59 pm, Steven Price wrote:
> The RMM keeps track of the timer while the realm REC is running, but on
> exit to the normal world KVM is responsible for handling the timers.
>
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
> arch/arm64/kvm/arch_timer.c | 53 ++++++++++++++++++++++++++++++++----
> include/kvm/arm_arch_timer.h | 2 ++
> 2 files changed, 49 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c
> index bb24a76b4224..d4af9ee58550 100644
> --- a/arch/arm64/kvm/arch_timer.c
> +++ b/arch/arm64/kvm/arch_timer.c
> @@ -130,6 +130,11 @@ static void timer_set_offset(struct arch_timer_context *ctxt, u64 offset)
> {
> struct kvm_vcpu *vcpu = ctxt->vcpu;
>
> + if (kvm_is_realm(vcpu->kvm)) {
> + WARN_ON(offset);
> + return;
> + }
> +
> switch(arch_timer_ctx_index(ctxt)) {
> case TIMER_VTIMER:
> __vcpu_sys_reg(vcpu, CNTVOFF_EL2) = offset;
> @@ -411,6 +416,21 @@ static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_level,
> }
> }
>
> +void kvm_realm_timers_update(struct kvm_vcpu *vcpu)
> +{
> + struct arch_timer_cpu *arch_timer = &vcpu->arch.timer_cpu;
> + int i;
> +
> + for (i = 0; i < NR_KVM_TIMERS; i++) {

Do we required to check for all timers, is realm/rmm uses hyp timers?

> + struct arch_timer_context *timer = &arch_timer->timers[i];
> + bool status = timer_get_ctl(timer) & ARCH_TIMER_CTRL_IT_STAT;
> + bool level = kvm_timer_irq_can_fire(timer) && status;
> +
> + if (level != timer->irq.level)
> + kvm_timer_update_irq(vcpu, level, timer);
> + }
> +}
> +
> /* Only called for a fully emulated timer */
> static void timer_emulate(struct arch_timer_context *ctx)
> {
> @@ -621,6 +641,11 @@ void kvm_timer_vcpu_load(struct kvm_vcpu *vcpu)
> if (unlikely(!timer->enabled))
> return;
>
> + kvm_timer_unblocking(vcpu);
> +
> + if (vcpu_is_rec(vcpu))
> + return;
> +

For realm, timer->enabled is not set, load returns before this check.

> get_timer_map(vcpu, &map);
>
> if (static_branch_likely(&has_gic_active_state)) {
> @@ -633,8 +658,6 @@ void kvm_timer_vcpu_load(struct kvm_vcpu *vcpu)
>
> set_cntvoff(timer_get_offset(map.direct_vtimer));
>
> - kvm_timer_unblocking(vcpu);
> -
> timer_restore_state(map.direct_vtimer);
> if (map.direct_ptimer)
> timer_restore_state(map.direct_ptimer);
> @@ -668,6 +691,9 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu)
> if (unlikely(!timer->enabled))
> return;
>
> + if (vcpu_is_rec(vcpu))
> + goto out;
> +
> get_timer_map(vcpu, &map);
>
> timer_save_state(map.direct_vtimer);
> @@ -686,9 +712,6 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu)
> if (map.emul_ptimer)
> soft_timer_cancel(&map.emul_ptimer->hrtimer);
>
> - if (kvm_vcpu_is_blocking(vcpu))
> - kvm_timer_blocking(vcpu);
> -
> /*
> * The kernel may decide to run userspace after calling vcpu_put, so
> * we reset cntvoff to 0 to ensure a consistent read between user
> @@ -697,6 +720,11 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu)
> * virtual offset of zero, so no need to zero CNTVOFF_EL2 register.
> */
> set_cntvoff(0);
> +
> +out:
> + if (kvm_vcpu_is_blocking(vcpu))
> + kvm_timer_blocking(vcpu);
> +
> }
>
> /*
> @@ -785,12 +813,18 @@ void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu)
> struct arch_timer_cpu *timer = vcpu_timer(vcpu);
> struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
> struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
> + u64 cntvoff;
>
> vtimer->vcpu = vcpu;
> ptimer->vcpu = vcpu;
>
> + if (kvm_is_realm(vcpu->kvm))
> + cntvoff = 0;
> + else
> + cntvoff = kvm_phys_timer_read();
> +
> /* Synchronize cntvoff across all vtimers of a VM. */
> - update_vtimer_cntvoff(vcpu, kvm_phys_timer_read());
> + update_vtimer_cntvoff(vcpu, cntvoff);
> timer_set_offset(ptimer, 0);
>
> hrtimer_init(&timer->bg_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);
> @@ -1265,6 +1299,13 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu)
> return -EINVAL;
> }
>
> + /*
> + * We don't use mapped IRQs for Realms because the RMI doesn't allow
> + * us setting the LR.HW bit in the VGIC.
> + */
> + if (vcpu_is_rec(vcpu))
> + return 0;
> +
> get_timer_map(vcpu, &map);
>
> ret = kvm_vgic_map_phys_irq(vcpu,
> diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h
> index cd6d8f260eab..158280e15a33 100644
> --- a/include/kvm/arm_arch_timer.h
> +++ b/include/kvm/arm_arch_timer.h
> @@ -76,6 +76,8 @@ int kvm_arm_timer_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr);
> int kvm_arm_timer_get_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr);
> int kvm_arm_timer_has_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr);
>
> +void kvm_realm_timers_update(struct kvm_vcpu *vcpu);
> +
> u64 kvm_phys_timer_read(void);
>
> void kvm_timer_vcpu_load(struct kvm_vcpu *vcpu);

Thanks,
Ganapat