linux-kernel - Re: [PATCH v5 3/3] irqchip/loongson-eiointc: Add extioi virt extension support

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Message-ID: <87wmkortqo.ffs@tglx>
Date: Sat, 10 Aug 2024 22:46:39 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Bibo Mao <maobibo@...ngson.cn>, Tianrui Zhao <zhaotianrui@...ngson.cn>,
 Huacai Chen <chenhuacai@...nel.org>
Cc: WANG Xuerui <kernel@...0n.name>, kvm@...r.kernel.org,
 loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org,
 virtualization@...ts.linux.dev, x86@...nel.org, Song Gao
 <gaosong@...ngson.cn>
Subject: Re: [PATCH v5 3/3] irqchip/loongson-eiointc: Add extioi virt
 extension support

On Mon, Aug 05 2024 at 15:35, Bibo Mao wrote:

> Interrupts can be routed to maximal four virtual CPUs with one external
> hardware interrupt. Add the extioi virt extension support so that
> Interrupts can be routed to 256 vcpus on hypervisor mode.

interrupts .... 256 vCPUs in hypervisor mode.

>  static int cpu_to_eio_node(int cpu)
>  {
> -	return cpu_logical_map(cpu) / CORES_PER_EIO_NODE;
> +	int cores;
> +
> +	if (kvm_para_available() && kvm_para_has_feature(KVM_FEATURE_VIRT_EXTIOI))

Why isn't that kvm_para_available() check inside of
kvm_para_has_feature() instead of inflicting it on every usage site?
That's just error prone.

> +		cores = CORES_PER_VEIO_NODE;
> +	else
> +		cores = CORES_PER_EIO_NODE;
> +	return cpu_logical_map(cpu) / cores;
>  }

> @@ -105,18 +144,24 @@ static int eiointc_set_irq_affinity(struct irq_data *d, const struct cpumask *af
> @@ -140,17 +185,23 @@ static int eiointc_index(int node)
>  
>  static int eiointc_router_init(unsigned int cpu)
>  {
> -	int i, bit;
> -	uint32_t data;
> -	uint32_t node = cpu_to_eio_node(cpu);
> -	int index = eiointc_index(node);
> +	uint32_t data, node;
> +	int i, bit, cores, index;

Is it so hard to follow:

  https://www.kernel.org/doc/html/latest/process/maintainer-tip.html#variable-declarations

?

Thanks,

        tglx