From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: [PATCH 05/10] xen/arm: vgic-v3: Document the current restrictions Date: Thu, 22 Jan 2015 15:19:16 +0000 Message-ID: <54C114F4.2040700@linaro.org> References: <1421684957-29884-1-git-send-email-julien.grall@linaro.org> <1421684957-29884-6-git-send-email-julien.grall@linaro.org> <1421769643.10440.309.camel@citrix.com> <54BE952E.6040304@linaro.org> <1421842611.13271.20.camel@citrix.com> <54BF9CA7.7000008@linaro.org> <1421844486.13271.38.camel@citrix.com> <54BFA773.2010904@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta3.messagelabs.com ([195.245.230.39]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1YEJXv-0005vz-2b for xen-devel@lists.xenproject.org; Thu, 22 Jan 2015 15:19:47 +0000 Received: by mail-we0-f177.google.com with SMTP id l61so2346424wev.8 for ; Thu, 22 Jan 2015 07:19:45 -0800 (PST) In-Reply-To: <54BFA773.2010904@linaro.org> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Campbell Cc: xen-devel@lists.xenproject.org, tim@xen.org, stefano.stabellini@citrix.com List-Id: xen-devel@lists.xenproject.org Hi, On 21/01/15 13:19, Julien Grall wrote: >>>>> If you give a look to the redistributor iniatialization (see Xen and >>>>> Linux GICv3 code). The code will go through all the redistributors and >>>>> check GICR_TYPER to see if the processor is associated to this >>>>> redistributor. >>>>> >>>>> I'm not sure how the redistributor should behave if it's accessed by >>>>> another processor. >>>> >>>> Please can you find a spec reference and include it in the clarified >>>> version of this item. >>> >>> Rather than the distributor, there is multiple redistributor (one per >>> processor). >>> >>> I think the section 5.4.1 in the GICv3 should answer to this question: >>> >>> "Each re-distributor must be allocated at one page for controlling the >>> overall behavior of the re-distributor and for controlling physical >>> LPIs. The base address of this page is referred to as RD_base. In >>> addition, each re-distributor must be also allocated the following >>> additional pages". >> >> That doesn't say anything about one CPU touching another's >> redistributor. > > Linux is at least using GICR_TYPER, to retrieve the right distributor. > For the other the register I've no idea. I've asked ARM. Let see what > they will answer. For documentation purpose, the re-distributor should be accessible by any processor. It has been confirmed by ARM and I've found the paragraph in spec stating: "GICR_* registers. Multiple pages of registers per re-distributor accessible to all processors." Section 4.3.5 of the r24 document. I have a working implementation of this behavior. I will add it in the v2 of this series and drop this patch. Regards, -- Julien Grall