From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EE2A3C2D0E7 for ; Thu, 26 Mar 2020 09:30:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C6F222073E for ; Thu, 26 Mar 2020 09:30:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727904AbgCZJaN (ORCPT ); Thu, 26 Mar 2020 05:30:13 -0400 Received: from mx2.suse.de ([195.135.220.15]:48286 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726354AbgCZJaM (ORCPT ); Thu, 26 Mar 2020 05:30:12 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id B694EAF2C; Thu, 26 Mar 2020 09:30:10 +0000 (UTC) Subject: Re: [PATCH v3 2/2] x86/xen: Make the secondary CPU idle tasks reliable To: Miroslav Benes , boris.ostrovsky@oracle.com, sstabellini@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, jpoimboe@redhat.com Cc: x86@kernel.org, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, live-patching@vger.kernel.org, jslaby@suse.cz, andrew.cooper3@citrix.com, jbeulich@suse.com References: <20200326092603.7230-1-mbenes@suse.cz> <20200326092603.7230-3-mbenes@suse.cz> From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= Message-ID: Date: Thu, 26 Mar 2020 10:30:09 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200326092603.7230-3-mbenes@suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 26.03.20 10:26, Miroslav Benes wrote: > The unwinder reports the secondary CPU idle tasks' stack on XEN PV as > unreliable, which affects at least live patching. > cpu_initialize_context() sets up the context of the CPU through > VCPUOP_initialise hypercall. After it is woken up, the idle task starts > in cpu_bringup_and_idle() function and its stack starts at the offset > right below pt_regs. The unwinder correctly detects the end of stack > there but it is confused by NULL return address in the last frame. > > Introduce a wrapper in assembly, which just calls > cpu_bringup_and_idle(). The return address is thus pushed on the stack > and the wrapper contains the annotation hint for the unwinder regarding > the stack state. > > Signed-off-by: Miroslav Benes Reviewed-by: Juergen Gross Juergen