From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: [PATCH v1 3/8] xen/arm: Support sign-extension for every read access Date: Mon, 28 Sep 2015 19:22:01 +0100 Message-ID: <56098549.2080503@citrix.com> References: <1443192698-16163-1-git-send-email-julien.grall@citrix.com> <1443192698-16163-4-git-send-email-julien.grall@citrix.com> <1443199485.25250.212.camel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1Zgd5W-0006VL-Da for xen-devel@lists.xenproject.org; Mon, 28 Sep 2015 18:23:46 +0000 In-Reply-To: <1443199485.25250.212.camel@citrix.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: Ian Campbell , xen-devel@lists.xenproject.org Cc: Vijaya.Kumar@caviumnetworks.com, stefano.stabellini@citrix.com, manish.jaggi@caviumnetworks.com, vijay.kilari@gmail.com List-Id: xen-devel@lists.xenproject.org On 25/09/15 17:44, Ian Campbell wrote: > On Fri, 2015-09-25 at 15:51 +0100, Julien Grall wrote: > I think you meant s/bit sign/sign bit/ but more correct would be "Sign > extend if required". > >> + * Note that we expect the read handler to have zeroed the bit >> + * unused in the register. > > "... to have zeroed the unused bits in the register". > > But I think "unused" is a bit misleading, you mean the ones outside the > requested access size, those bits are still "used" IYSWIM. I can't think of > a terse term for "outside the requested access size I'm afraid. I will switch to "Note that we expect the read handler to have zeroed the bits outside the requested access size." > > Did you confirm that all existing handlers meet this requirement? Yes, we always do *r in the existing handlers. > Perhaps an ASSERT would be handy? What about: ASSERT((*r & ((~0UL) >> (BITS_PER_LONG - size))) == 0) Regards, -- Julien Grall