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 35882C43331 for ; Thu, 26 Mar 2020 09:30:30 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0859C20714 for ; Thu, 26 Mar 2020 09:30:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0859C20714 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jHOq4-0008TJ-Gq; Thu, 26 Mar 2020 09:30:12 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jHOq3-0008TB-VP for xen-devel@lists.xenproject.org; Thu, 26 Mar 2020 09:30:11 +0000 X-Inumbo-ID: 63c0e592-6f44-11ea-a6c1-bc764e2007e4 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 63c0e592-6f44-11ea-a6c1-bc764e2007e4; Thu, 26 Mar 2020 09:30:11 +0000 (UTC) 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) 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 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 Subject: Re: [Xen-devel] [PATCH v3 2/2] x86/xen: Make the secondary CPU idle tasks reliable X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: andrew.cooper3@citrix.com, x86@kernel.org, linux-kernel@vger.kernel.org, jbeulich@suse.com, live-patching@vger.kernel.org, xen-devel@lists.xenproject.org, jslaby@suse.cz Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" 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