From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753907AbdJNPEX (ORCPT ); Sat, 14 Oct 2017 11:04:23 -0400 Received: from mail-wm0-f46.google.com ([74.125.82.46]:51134 "EHLO mail-wm0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753809AbdJNPEV (ORCPT ); Sat, 14 Oct 2017 11:04:21 -0400 X-Google-Smtp-Source: AOwi7QDgxh+jWSg0203Q1Dn7eN59kaTCQn2OyYr3Qr+GNITfY/GKeBYMasE12MpiV/gEfiysbDAvwA== Date: Sat, 14 Oct 2017 08:04:18 -0700 From: Christoffer Dall To: Auger Eric Cc: Andre Przywara , eric.auger.pro@gmail.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, marc.zyngier@arm.com, peter.maydell@linaro.org, wanghaibin.wang@huawei.com, wu.wubin@huawei.com Subject: Re: [PATCH v2 02/10] KVM: arm/arm64: vgic-its: Always allow clearing GITS_CREADR/CWRITER Message-ID: <20171014150418.GD5886@lvm> References: <1506518920-18571-1-git-send-email-eric.auger@redhat.com> <1506518920-18571-3-git-send-email-eric.auger@redhat.com> <4315e223-a843-50d9-506d-a3902ee8d18d@arm.com> <20171013114412.GG8927@cbox> <065e1e4c-e16d-5df6-ceff-3415a2d91e8d@redhat.com> <20171013175446.GC17578@cbox> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Oct 14, 2017 at 10:53:01AM +0200, Auger Eric wrote: > Hi Christoffer, > > On 13/10/2017 19:54, Christoffer Dall wrote: > > On Fri, Oct 13, 2017 at 01:54:34PM +0200, Auger Eric wrote: > >> Hi Christoffer, > >> On 13/10/2017 13:44, Christoffer Dall wrote: > >>> On Fri, Oct 06, 2017 at 05:29:02PM +0200, Auger Eric wrote: > >>>> Hi, > >>>> > >>>> On 06/10/2017 16:37, Andre Przywara wrote: > >>>>> Hi, > >>>>> > >>>>> On 27/09/17 14:28, Eric Auger wrote: > >>>>>> If the GITS_CBASER Size field is 0, which can correspond to a > >>>>>> reset value, the userspace fails to set the GITS_CREADR/CWRITER > >>>>>> offsets to 0. This failure is not justified. > >>>>>> > >>>>>> Let's allow this setting which can also correspond to a reset value. > >>>>> > >>>>> But the GITS_CBASER size field has a +1 encoding, so can never be 0, if > >>>>> I understand the manual (and ITS_CMD_BUFFER_SIZE) correctly. > >>>> Oh OK, you're. I missed that. I would have sworn I've seen that failure > >>>> but I must have misinterpreted it. > >>>> > >>> > >>> What is CWRITER is written to a brand new ITS before the CBASER is > >>> written? > >>> > >>> I don't see us initializing the cbaser field anywhere? > >> in vgic_its_create() its is allocated with kzalloc so its->cbaser is > >> initialized at this moment. > >> > > > > Right, so it can be 0, and we still need your patch, contrary to Andre's > > comment. Am I missing something? > > No Andre is right, cbaser = 0 but ITS_CMD_BUFFER_SIZE(its->cbaser) > returns 4kB. > > #define ITS_CMD_BUFFER_SIZE(baser) ((((baser) & 0xff) + 1) << 12) > > So the check doesn't fail. > Duh, I didn't check the macro and thought it just applied a mask and shift. Thanks, -Christoffer