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

[Ganapatrao Kulkarni]

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@xxxxxxx>
> ---
>   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