From patchwork Thu Mar 19 09:56:06 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Miroslav Benes X-Patchwork-Id: 11446979 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 46DB392A for ; Thu, 19 Mar 2020 09:57:34 +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 2D1C720722 for ; Thu, 19 Mar 2020 09:57:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2D1C720722 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz 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 1jEruU-0007zk-Dl; Thu, 19 Mar 2020 09:56:18 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jEruT-0007zX-Et for xen-devel@lists.xenproject.org; Thu, 19 Mar 2020 09:56:17 +0000 X-Inumbo-ID: dd1cf138-69c7-11ea-92cf-bc764e2007e4 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id dd1cf138-69c7-11ea-92cf-bc764e2007e4; Thu, 19 Mar 2020 09:56:12 +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 6CB58AF85; Thu, 19 Mar 2020 09:56:11 +0000 (UTC) From: Miroslav Benes To: boris.ostrovsky@oracle.com, jgross@suse.com, sstabellini@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, jpoimboe@redhat.com Date: Thu, 19 Mar 2020 10:56:06 +0100 Message-Id: <20200319095606.23627-3-mbenes@suse.cz> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200319095606.23627-1-mbenes@suse.cz> References: <20200319095606.23627-1-mbenes@suse.cz> MIME-Version: 1.0 Subject: [Xen-devel] [PATCH v2 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, live-patching@vger.kernel.org, xen-devel@lists.xenproject.org, Miroslav Benes , jslaby@suse.cz Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" 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 --- arch/x86/xen/smp_pv.c | 3 ++- arch/x86/xen/xen-head.S | 8 ++++++++ 2 files changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c index 802ee5bba66c..6b88cdcbef8f 100644 --- a/arch/x86/xen/smp_pv.c +++ b/arch/x86/xen/smp_pv.c @@ -53,6 +53,7 @@ static DEFINE_PER_CPU(struct xen_common_irq, xen_irq_work) = { .irq = -1 }; static DEFINE_PER_CPU(struct xen_common_irq, xen_pmu_irq) = { .irq = -1 }; static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id); +extern unsigned char asm_cpu_bringup_and_idle[]; static void cpu_bringup(void) { @@ -309,7 +310,7 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle) * pointing just below where pt_regs would be if it were a normal * kernel entry. */ - ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle; + ctxt->user_regs.eip = (unsigned long)asm_cpu_bringup_and_idle; ctxt->flags = VGCF_IN_KERNEL; ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */ ctxt->user_regs.ds = __USER_DS; diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S index edc776af0e0a..9dc6f9a420a8 100644 --- a/arch/x86/xen/xen-head.S +++ b/arch/x86/xen/xen-head.S @@ -58,6 +58,14 @@ SYM_CODE_START(startup_xen) call xen_start_kernel SYM_CODE_END(startup_xen) __FINIT + +.pushsection .text +SYM_CODE_START(asm_cpu_bringup_and_idle) + UNWIND_HINT_EMPTY + + call cpu_bringup_and_idle +SYM_CODE_END(asm_cpu_bringup_and_idle) +.popsection #endif .pushsection .text