linux-kernel - Re: [PATCH 2/6] irqchip/ls-scfg-msi: Fix MSI affinity handling

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Date:   Tue, 19 Jun 2018 14:00:23 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Marc Zyngier <marc.zyngier@....com>
cc:     Jason Cooper <jason@...edaemon.net>, linux-kernel@...r.kernel.org,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Yang Yingliang <yangyingliang@...wei.com>
Subject: Re: [PATCH 2/6] irqchip/ls-scfg-msi: Fix MSI affinity handling

On Tue, 19 Jun 2018, Marc Zyngier wrote:

> The ls-scfs-msi driver is not dealing with the effective affinity
> as it should. Let's fix that, and make it clear that the effective
> affinity is restricted to a single CPU.
> 
> Reported-by: Alexandre Belloni <alexandre.belloni@...tlin.com>
> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> ---
>  drivers/irqchip/irq-ls-scfg-msi.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/irqchip/irq-ls-scfg-msi.c b/drivers/irqchip/irq-ls-scfg-msi.c
> index 1ec3bfe56693..2811cc53e425 100644
> --- a/drivers/irqchip/irq-ls-scfg-msi.c
> +++ b/drivers/irqchip/irq-ls-scfg-msi.c
> @@ -121,7 +121,8 @@ static int ls_scfg_msi_set_affinity(struct irq_data *irq_data,
>  		return -EINVAL;
>  	}
>  
> -	cpumask_copy(irq_data->common->affinity, mask);
> +	cpumask_copy(irq_data->common->affinity, cpumask_of(cpu));

That's wrong. The driver should not fiddle with the affinity mask at all
and just store the effective mask.

> +	irq_data_update_effective_affinity(irq_data, cpumask_of(cpu));
>  
>  	return IRQ_SET_MASK_OK;

If yuo look at the call site, then you'll notice that it will do:

        case IRQ_SET_MASK_OK:
        case IRQ_SET_MASK_OK_DONE:
                cpumask_copy(desc->irq_common_data.affinity, mask);

So the cpumask_copy() can just go away.

Thanks,

	tglx