Path: csiph.com!eternal-september.org!feeder.eternal-september.org!feeds.phibee-telecom.net!news.panservice.it!bofh.it!news.nic.it!robomod From: Andrew Cooper Newsgroups: linux.kernel Subject: Re: [Xen-devel] Does __KERNEL_DS serve a purpose? Date: Fri, 08 Apr 2016 10:20:02 +0200 Message-ID: References: X-Greylist: delayed 1054 seconds by postgrey-1.27 at vger.kernel.org; Fri, 08 Apr 2016 04:18:58 EDT X-Cam-Antivirus: no malware found X-Cam-Scannerinfo: http://www.cam.ac.uk/cs/email/scanner/ User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.7.2 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: robomod@news.nic.it List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Approved: robomod@news.nic.it Lines: 16 Organization: linux.* mail to news gateway X-Original-Cc: Borislav Petkov , kvm list , xen-devel X-Original-Date: Fri, 8 Apr 2016 09:01:19 +0100 X-Original-Message-ID: <5707654F.1060407@citrix.com> X-Original-References: X-Original-Sender: linux-kernel-owner@vger.kernel.org Xref: csiph.com linux.kernel:1374073 On 08/04/2016 01:24, Andy Lutomirski wrote: > I can't see any reason that we need the __KERNEL_DS segment at all -- > I think that everything that uses __KERNEL_DS could use __USER_DS > instead. Am I missing anything? This has been bugging me for a > while. > > I mulled over this a bit when trying to understand the sysret_ss_attrs > bug and then forgot about it. Linux doesn't have a separate __KERNEL_SS. For the plain data segments, the dpl is not interesting. However, %ss is also loaded with __KERNEL_DS, and %ss.dpl is somewhat important. ~Andrew