[RFC PATCH 4/7] KVM: arm/arm64: Check that system supports split eoi/deactivate

[Marc Zyngier]

On 10/12/16 20:47, Christoffer Dall wrote:
> Some systems without proper firmware and/or hardware description data
> don't support the split EOI and deactivate operation and therefore
> don't provide an irq_set_vcpu_affinity implementation.  On such
> systems, we cannot leave the physical interrupt active after the timer
> handler on the host has run, so we cannot support KVM with the timer
> changes we about to introduce.
> 
> Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>
> ---
>  virt/kvm/arm/arch_timer.c | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
> 
> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
> index c7c3bfd..f27a086 100644
> --- a/virt/kvm/arm/arch_timer.c
> +++ b/virt/kvm/arm/arch_timer.c
> @@ -418,6 +418,31 @@ static int kvm_timer_dying_cpu(unsigned int cpu)
>  	return 0;
>  }
>  
> +static bool has_split_eoi_deactivate_support(void)
> +{
> +	struct irq_desc *desc;
> +	struct irq_data *data;
> +	struct irq_chip *chip;
> +
> +	/*
> +	 * Check if split EOI and deactivate is supported on this machine.
> +	 */
> +	desc = irq_to_desc(host_vtimer_irq);
> +	if (!desc) {
> +		kvm_err("kvm_arch_timer: no host_vtimer_irq descriptor\n");
> +		return false;
> +	}
> +
> +	data = irq_desc_get_irq_data(desc);
> +	chip = irq_data_get_irq_chip(data);
> +	if (!chip || !chip->irq_set_vcpu_affinity) {
> +		kvm_err("kvm_arch_timer: no split EOI/deactivate; abort\n");
> +		return false;
> +	}
> +
> +	return true;
> +}

That feels really involved. How about reporting that we don't have a
usable VGIC altogether from the GIC driver?

> +
>  int kvm_timer_hyp_init(void)
>  {
>  	struct arch_timer_kvm_info *info;
> @@ -449,6 +474,11 @@ int kvm_timer_hyp_init(void)
>  		return err;
>  	}
>  
> +	if (!has_split_eoi_deactivate_support()) {
> +		disable_percpu_irq(host_vtimer_irq);
> +		return -ENODEV;
> +	}
> +
>  	kvm_info("virtual timer IRQ%d\n", host_vtimer_irq);
>  
>  	cpuhp_setup_state(CPUHP_AP_KVM_ARM_TIMER_STARTING,
> 

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...