From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935940AbbCDICS (ORCPT ); Wed, 4 Mar 2015 03:02:18 -0500 Received: from mail-we0-f181.google.com ([74.125.82.181]:41642 "EHLO mail-we0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933180AbbCDICP (ORCPT ); Wed, 4 Mar 2015 03:02:15 -0500 Date: Wed, 4 Mar 2015 09:02:10 +0100 From: Ingo Molnar To: Andy Lutomirski Cc: x86@kernel.org, linux-kernel@vger.kernel.org, Borislav Petkov , Oleg Nesterov , Denys Vlasenko , Linus Torvalds Subject: Re: [RFC 1/3] x86: Add this_cpu_sp0() to read sp0 for the current cpu Message-ID: <20150304080210.GA12265@gmail.com> References: <385661f737a3c430ee2fb50e1531ae002fa263a0.1424994489.git.luto@amacapital.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <385661f737a3c430ee2fb50e1531ae002fa263a0.1424994489.git.luto@amacapital.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Andy Lutomirski wrote: > We currently store references to the top of the kernel stack in > multiple places: kernel_stack (with an offset) and > init_tss.x86_tss.sp0 (no offset). The latter is defined by hardware > and is a clean canonical way to find the top of the stack. Add an Btw., 'per_cpu(init_tss)' is a somewhat misleading name these days, as there's nothing 'init' about it anymore - we load it during CPU init and then manually maintain its contents. A better name would be 'current_tss' - referring to both the current CPU and the current task? > This needs minor paravirt tweaks to ensure that On native, sp0 nit: s/On/on/ > defines the top of the kernel stack. On Xen and lguest, the > hypervisor tracks it, but we want to start reading sp0 in the > kernel. Fixing this is simple: just update our local copy of sp0 as > well as the hypervisor's copy on task switches. Thanks, Ingo