linux-kernel - Re: [Xen-devel] [PATCH] xen/events: Support event channel rebind on ARM

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Message-ID: <55B6019B.20903@citrix.com>
Date:	Mon, 27 Jul 2015 11:02:03 +0100
From:	David Vrabel <david.vrabel@...rix.com>
To:	Julien Grall <julien.grall@...rix.com>,
	<xen-devel@...ts.xenproject.org>
CC:	<x86@...nel.org>, <ian.campbell@...rix.com>,
	<stefano.stabellini@...citrix.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	<linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...hat.com>,
	David Vrabel <david.vrabel@...rix.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [Xen-devel] [PATCH] xen/events: Support event channel rebind
 on ARM

On 25/07/15 18:34, Julien Grall wrote:
> Currently, the event channel rebind code is gated with the presence of
> the vector callback.
> 
> The virtual interrupt controller on ARM has the concept of per-CPU
> interrupt (PPI) which allow us to support per-VCPU event channel.
> Therefore there is no need of vector callback for ARM.
> 
> Xen is already using a free PPI to notify the guest VCPU of an event.
> Furthermore, the xen code initialization in Linux (see
> arch/arm/xen/enlighten.c) is requesting correctly a per-CPU IRQ.
> 
> Introduce new macro xen_support_evtchn_rebind to allow architecture
> decide whether rebind an event is support or not. It will always return
> 1 on ARM and keep the same behavior on x86.
> 
> This is also allow us to drop the usage of xen_have_vector_callback
> entirely in the ARM code.

Reviewed-by: David Vrabel <david.vrabel@...rix.com>

Provided you make xen_support_evtchn_rebind() an inline function.

David
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