From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH v5 1/6] xen: Add convenient macro boot_cpu Date: Tue, 6 May 2014 17:09:28 +0100 Message-ID: <53690938.10007@citrix.com> References: <1399045930-17364-1-git-send-email-julien.grall@linaro.org> <1399045930-17364-2-git-send-email-julien.grall@linaro.org> <536760F7020000780000EDD1@mail.emea.novell.com> <536906C1.6050109@linaro.org> <53692438020000780000F8BA@mail.emea.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta4.messagelabs.com ([85.158.143.247]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1WhhwE-0007ua-Lh for xen-devel@lists.xenproject.org; Tue, 06 May 2014 16:09:50 +0000 In-Reply-To: <53692438020000780000F8BA@mail.emea.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Julien Grall Cc: Keir Fraser , ian.campbell@citrix.com, tim@xen.org, Ian Jackson , stefano.stabellini@citrix.com, Jan Beulich , xen-devel@lists.xenproject.org List-Id: xen-devel@lists.xenproject.org On 06/05/14 17:04, Jan Beulich wrote: >>>> On 06.05.14 at 17:58, wrote: >> On 05/05/2014 08:59 AM, Jan Beulich wrote: >>>>>> On 02.05.14 at 17:52, wrote: >>>> --- a/xen/include/xen/percpu.h >>>> +++ b/xen/include/xen/percpu.h >>>> @@ -16,6 +16,9 @@ >>>> /* Preferred on Xen. Also see arch-defined per_cpu(). */ >>>> #define this_cpu(var) __get_cpu_var(var) >>>> >>>> +/* Access variable on boot CPU */ >>>> +#define boot_cpu(var) per_cpu(var, 0) >>>> + >>>> /* Linux compatibility. */ >>>> #define get_cpu_var(var) this_cpu(var) >>>> #define put_cpu_var(var) >>> I can only second Andrew's comment - without it becoming clear when >>> and why this would be used, this isn't going to be acceptable (and if >>> it really was correct and worthwhile, this small a change wouldn't need >>> separating out from the code that's intended to actually make use of it). >> It's used in the next patch (ie #2). I thought it was better to move out >> this small change rather than introducing it in the patch. >> >> This macro is here for a shortcut of per_cpu(myvar, 0). We have few >> usage on ARM, most of them are during boot. >> >> There is another when a secondary CPUs is booting. We need to retrieve >> the PPIs type (level/edge...) from the boot CPU. >> >> As said in the answer to Andrew, I can either move this macro in an ARM >> specific header or open code per_cpu(...,0). > Either is fine with me, but putting this in common code isn't. > > Jan Agreed - this should not be common. If you eventually want to support hotplug, making an arm specific boot_cpu() might help those efforts in the future. ~Andrew