[PATCH] KVM: arm64: Wake-up from WFI when iqrchip is in userspace

[Yao Yuan]

On Thu, Apr 23, 2026 at 05:36:07PM +0800, Marc Zyngier wrote:
> It appears that there is nothing in the wake-up path that
> evaluates whether the in-kernel interrupts are pending unless
> we have a vgic.
>
> This means that the userspace irqchip support has been broken for
> about four years, and nobody noticed. It was also broken before
> as we wouldn't wake-up on a PMU interrupt, but hey, who cares...
>
> It is probably time to remove the feature altogether, because it
> was a terrible idea 10 years ago, and it still is.
>
> Fixes: b57de4ffd7c6d ("KVM: arm64: Simplify kvm_cpu_has_pending_timer()")
> Signed-off-by: Marc Zyngier <maz at kernel.org>
> ---
>  arch/arm64/kvm/arm.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 176cbe8baad30..8bb2c7422cc8b 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -824,6 +824,10 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *v)
>  {
>  	bool irq_lines = *vcpu_hcr(v) & (HCR_VI | HCR_VF | HCR_VSE);
>

Hi Marc,

> +	irq_lines |= (!irqchip_in_kernel(v->kvm) &&
> +		      (kvm_timer_should_notify_user(v) ||
> +		       kvm_pmu_should_notify_user(v)));

How about a new helper like 'kvm_should_notify_us_irqchip()' ?
We can replace the same part at beginning of kvm_vcpu_exit_request() and
here w/ unlikely().

> +
>  	return ((irq_lines || kvm_vgic_vcpu_pending_irq(v))
>  		&& !kvm_arm_vcpu_stopped(v) && !v->arch.pause);
>  }
> --
> 2.47.3
>