linux-kernel - Re: [PATCH 2/7] xen/events: don't unmask an event channel when an eoi is pending

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Message-ID: <7aa76e26-b6f4-fae2-861b-bcc0039ce497@suse.com>
Date:   Mon, 8 Feb 2021 11:06:12 +0100
From:   Jan Beulich <jbeulich@...e.com>
To:     Juergen Gross <jgross@...e.com>
Cc:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        stable@...r.kernel.org, Julien Grall <julien@....org>,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/7] xen/events: don't unmask an event channel when an eoi
 is pending

On 06.02.2021 11:49, Juergen Gross wrote:
> @@ -1798,6 +1818,29 @@ static void mask_ack_dynirq(struct irq_data *data)
>  	ack_dynirq(data);
>  }
>  
> +static void lateeoi_ack_dynirq(struct irq_data *data)
> +{
> +	struct irq_info *info = info_for_irq(data->irq);
> +	evtchn_port_t evtchn = info ? info->evtchn : 0;
> +
> +	if (VALID_EVTCHN(evtchn)) {
> +		info->eoi_pending = true;
> +		mask_evtchn(evtchn);
> +	}
> +}
> +
> +static void lateeoi_mask_ack_dynirq(struct irq_data *data)
> +{
> +	struct irq_info *info = info_for_irq(data->irq);
> +	evtchn_port_t evtchn = info ? info->evtchn : 0;
> +
> +	if (VALID_EVTCHN(evtchn)) {
> +		info->masked = true;
> +		info->eoi_pending = true;
> +		mask_evtchn(evtchn);
> +	}
> +}
> +
>  static int retrigger_dynirq(struct irq_data *data)
>  {
>  	evtchn_port_t evtchn = evtchn_from_irq(data->irq);
> @@ -2023,8 +2066,8 @@ static struct irq_chip xen_lateeoi_chip __read_mostly = {
>  	.irq_mask		= disable_dynirq,
>  	.irq_unmask		= enable_dynirq,
>  
> -	.irq_ack		= mask_ack_dynirq,
> -	.irq_mask_ack		= mask_ack_dynirq,
> +	.irq_ack		= lateeoi_ack_dynirq,
> +	.irq_mask_ack		= lateeoi_mask_ack_dynirq,
>  
>  	.irq_set_affinity	= set_affinity_irq,
>  	.irq_retrigger		= retrigger_dynirq,
> 

Unlike the prior handler the two new ones don't call ack_dynirq()
anymore, and the description doesn't give a hint towards this
difference. As a consequence, clear_evtchn() also doesn't get
called anymore - patch 3 adds the calls, but claims an older
commit to have been at fault. _If_ ack_dynirq() indeed isn't to
be called here, shouldn't the clear_evtchn() calls get added
right here?

Jan