From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Jan Beulich" <JBeulich@suse.com>
Subject: Re: [PATCH 03/12] xen/events: remove unnecessary
 init_evtchn_cpu_bindings()
Date: Wed, 20 Mar 2013 11:09:11 +0000
Message-ID: <5149A6E702000078000C71EF@nat28.tlf.novell.com>
References: <1363727099-25519-1-git-send-email-david.vrabel@citrix.com>
	<1363727099-25519-4-git-send-email-david.vrabel@citrix.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
In-Reply-To: <1363727099-25519-4-git-send-email-david.vrabel@citrix.com>
Content-Disposition: inline
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: David Vrabel <david.vrabel@citrix.com>
Cc: Keir Fraser <keir@xen.org>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, Wei Liu <wei.liu2@citrix.com>, xen-devel@lists.xen.org
List-Id: xen-devel@lists.xenproject.org

>>> On 19.03.13 at 22:04, David Vrabel <david.vrabel@citrix.com> wrote:
> From: David Vrabel <david.vrabel@citrix.com>
> 
> Event channels are always explicitly bound to a specific VCPU before
> they are first enabled.  There is no need to initialize all possible
> events as bound to VCPU 0 at start of day or after a resume.

That part may indeed be safe to do, but ...

> --- a/drivers/xen/events.c
> +++ b/drivers/xen/events.c
> @@ -333,24 +333,6 @@ static void bind_evtchn_to_cpu(unsigned int chn, 
> unsigned int cpu)
>  	info_for_irq(irq)->cpu = cpu;
>  }
>  
> -static void init_evtchn_cpu_bindings(void)
> -{
> -	int i;
> -#ifdef CONFIG_SMP
> -	struct irq_info *info;
> -
> -	/* By default all event channels notify CPU#0. */
> -	list_for_each_entry(info, &xen_irq_list_head, list) {
> -		struct irq_desc *desc = irq_to_desc(info->irq);
> -		cpumask_copy(desc->irq_data.affinity, cpumask_of(0));
> -	}
> -#endif
> -
> -	for_each_possible_cpu(i)
> -		memset(per_cpu(cpu_evtchn_mask, i),
> -		       (i == 0) ? ~0 : 0, sizeof(*per_cpu(cpu_evtchn_mask, i)));

... you also remove the initialization of the mask bits here. If
that was intended, a sentence about the safety of this would
certainly be good to add to the description.

Jan