From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: [PATCH 04/10] xen/arm: vgic-v3: Don't check the size when we ignore the write/read as zero Date: Tue, 20 Jan 2015 18:04:05 +0000 Message-ID: <54BE9895.4060906@linaro.org> References: <1421684957-29884-1-git-send-email-julien.grall@linaro.org> <1421684957-29884-5-git-send-email-julien.grall@linaro.org> <1421769455.10440.306.camel@citrix.com> <54BE9341.7010307@linaro.org> 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 1YDdAJ-0000ji-4o for xen-devel@lists.xenproject.org; Tue, 20 Jan 2015 18:04:35 +0000 Received: by mail-we0-f176.google.com with SMTP id w62so12940819wes.7 for ; Tue, 20 Jan 2015 10:04:33 -0800 (PST) In-Reply-To: <54BE9341.7010307@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 On 20/01/15 17:41, Julien Grall wrote: > Hi Ian, > > On 20/01/15 15:57, Ian Campbell wrote: >> On Mon, 2015-01-19 at 16:29 +0000, Julien Grall wrote: >>> In general, it's not necessary/important to check the size. >> >> Only if the docs say this register can be accessed by a partial >> read/write, or if it is implementation defined what the result would be >> (and RAZ/WI is within the set of allowable actions). >> >> Do you have a reference for the behaviour of GICR accesses which aren't >> of the register's natural size? > > It's clearly specify in the spec if the register can be accessed with a > non-natural size. > > AFAICT, the spec doesn't give a specific behavior if the register > doesn't support byte/word/double word access. Hmmm, I read quickly the spec. 5.1.3 says: "Accessing any of these registers using other accesses is UNPREDICTABLE". So I think it's fine to go on this behavior. It would help to have a simpler code. Regards, -- Julien Grall