linux-kernel - Re: [PATCH v7 15/45] KVM: arm64: Support timers in realm RECs

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Message-ID: <d3181dde-1070-4101-a5f7-7e42d0ec2f99@arm.com>
Date: Tue, 4 Mar 2025 17:59:19 +0000
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Steven Price <steven.price@....com>, kvm@...r.kernel.org,
 kvmarm@...ts.linux.dev
Cc: Catalin Marinas <catalin.marinas@....com>, Marc Zyngier <maz@...nel.org>,
 Will Deacon <will@...nel.org>, James Morse <james.morse@....com>,
 Oliver Upton <oliver.upton@...ux.dev>, Zenghui Yu <yuzenghui@...wei.com>,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 Joey Gouly <joey.gouly@....com>, Alexandru Elisei
 <alexandru.elisei@....com>, Christoffer Dall <christoffer.dall@....com>,
 Fuad Tabba <tabba@...gle.com>, linux-coco@...ts.linux.dev,
 Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>,
 Gavin Shan <gshan@...hat.com>, Shanker Donthineni <sdonthineni@...dia.com>,
 Alper Gun <alpergun@...gle.com>, "Aneesh Kumar K . V"
 <aneesh.kumar@...nel.org>
Subject: Re: [PATCH v7 15/45] KVM: arm64: Support timers in realm RECs

On 13/02/2025 16:13, 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.
> 
> A later patch adds the support for propagating the timer values from the
> exit data structure and calling kvm_realm_timers_update().
> 
> Signed-off-by: Steven Price <steven.price@....com>
> ---
>   arch/arm64/kvm/arch_timer.c  | 45 ++++++++++++++++++++++++++++++++----
>   include/kvm/arm_arch_timer.h |  2 ++
>   2 files changed, 43 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c
> index d3d243366536..06b68bcd244f 100644
> --- a/arch/arm64/kvm/arch_timer.c
> +++ b/arch/arm64/kvm/arch_timer.c
> @@ -148,6 +148,13 @@ static void timer_set_cval(struct arch_timer_context *ctxt, u64 cval)
>   
>   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;
> +	}
> +
>   	if (!ctxt->offset.vm_offset) {
>   		WARN(offset, "timer %ld\n", arch_timer_ctx_index(ctxt));
>   		return;
> @@ -464,6 +471,21 @@ 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_EL0_TIMERS; i++) {
> +		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)
>   {
> @@ -889,6 +911,8 @@ void kvm_timer_vcpu_load(struct kvm_vcpu *vcpu)
>   	if (unlikely(!timer->enabled))
>   		return;
>   
> +	kvm_timer_unblocking(vcpu);
> +
>   	get_timer_map(vcpu, &map);
>   
>   	if (static_branch_likely(&has_gic_active_state)) {
> @@ -902,8 +926,6 @@ void kvm_timer_vcpu_load(struct kvm_vcpu *vcpu)
>   		kvm_timer_vcpu_load_nogic(vcpu);
>   	}
>   
> -	kvm_timer_unblocking(vcpu);
> -
>   	timer_restore_state(map.direct_vtimer);
>   	if (map.direct_ptimer)
>   		timer_restore_state(map.direct_ptimer);
> @@ -1094,7 +1116,9 @@ static void timer_context_init(struct kvm_vcpu *vcpu, int timerid)
>   
>   	ctxt->vcpu = vcpu;
>   
> -	if (timerid == TIMER_VTIMER)
> +	if (kvm_is_realm(vcpu->kvm))
> +		ctxt->offset.vm_offset = NULL;
> +	else if (timerid == TIMER_VTIMER)
>   		ctxt->offset.vm_offset = &kvm->arch.timer_data.voffset;

I think we need to disable the KVM_CAP_COUNTER_OFFSET for Realms and
also deny KVM_ARM_SET_COUNTER_OFFSET vm_ioctl.

Suzuki