From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Jan Beulich" <JBeulich@suse.com>
Subject: Re: [PATCH 8/8] evtchn: add FIFO-based event channel
 hypercalls and port ops
Date: Wed, 20 Mar 2013 10:47:50 +0000
Message-ID: <5149A1E602000078000C71C1@nat28.tlf.novell.com>
References: <1363726818-25409-1-git-send-email-david.vrabel@citrix.com>
	<1363726818-25409-9-git-send-email-david.vrabel@citrix.com>
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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 22:00, David Vrabel <david.vrabel@citrix.com> wrote:
> +static int setup_control_block(struct vcpu *v, uint64_t gfn, uint32_t offset)
> +{
> +    struct domain *d = v->domain;
> +    struct evtchn_fifo_vcpu *efv;
> +    struct page_info *page;
> +    void *virt;
> +    int i;

unsigned int (also elsewhere)

> +struct evtchn_fifo_queue {
> +    volatile uint32_t *head; /* points into control block */

I still think that explicit barriers are the way to go. Unless Linux'es
view on this has changed, you'll have issues getting the Linux folks
to accept this.

> @@ -83,6 +83,7 @@ struct evtchn
>          u16 virq;      /* state == ECS_VIRQ */
>      } u;
>      u32 port;
> +    struct evtchn_fifo_queue *queue;

Wouldn't it be better (more space efficient) to store the queue
array index rather than a pointer, considering that you expect to
have thousands of event channels?

Jan