From nobody Tue Feb 10 10:55:07 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) client-ip=192.237.175.120; envelope-from=xen-devel-bounces@lists.xenproject.org; helo=lists.xenproject.org; Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org ARC-Seal: i=1; a=rsa-sha256; t=1585214802; cv=none; d=zohomail.com; s=zohoarc; b=V/ex0MGeSRxMX4Y+TgW5l6tMTMS3vDTAu8faFBvdWmvwI6XYO26cizshNpetD7JYMHyPqaE8feiRAHBXbzJQIJARozIREv9fs/+siGKvCUP5+wnhYIvY0/MLFEl4H5IGc7EOw5lrJid1RZLGwdtkwDsui4nG533+UB4LtCBnN9Y= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1585214802; h=Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To; bh=+g6i+D67Llrp0b7Mxr20dKIBdtEuXCUKG/W0ZdcV2XI=; b=cYId/JVT8g5DVyLbD6/uibVwQxUYSseyMNQyt6Zxg8k3/PR591kBuTpM025QGC5RxowkwMKOkdmblC2ikBea1+OA/DsS7Ak2k6oUEmpSt/U86snky4QnIr+aVwEVw6YGVnYOQUyC451YNAXvGuyBAxwAI4KPKENR2t7LklhLxGY= ARC-Authentication-Results: i=1; mx.zohomail.com; spf=pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Return-Path: Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) by mx.zohomail.com with SMTPS id 1585214802976354.5631300574786; Thu, 26 Mar 2020 02:26:42 -0700 (PDT) Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jHOmF-0007LY-Af; Thu, 26 Mar 2020 09:26:15 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jHOmD-0007L8-MN for xen-devel@lists.xenproject.org; Thu, 26 Mar 2020 09:26:13 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id d28a29c6-6f43-11ea-b34e-bc764e2007e4; Thu, 26 Mar 2020 09:26:07 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 17520AF2C; Thu, 26 Mar 2020 09:26:07 +0000 (UTC) X-Inumbo-ID: d28a29c6-6f43-11ea-b34e-bc764e2007e4 X-Virus-Scanned: by amavisd-new at test-mx.suse.de 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, 26 Mar 2020 10:26:03 +0100 Message-Id: <20200326092603.7230-3-mbenes@suse.cz> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200326092603.7230-1-mbenes@suse.cz> References: <20200326092603.7230-1-mbenes@suse.cz> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Subject: [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, Miroslav Benes , jslaby@suse.cz Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" Content-Type: text/plain; charset="utf-8" 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 --- arch/x86/xen/smp_pv.c | 3 ++- arch/x86/xen/xen-head.S | 10 ++++++++++ 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c index 802ee5bba66c..8fb8a50a28b4 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= ) =3D { .irq =3D -1 }; static DEFINE_PER_CPU(struct xen_common_irq, xen_pmu_irq) =3D { .irq =3D -= 1 }; =20 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id); +void asm_cpu_bringup_and_idle(void); =20 static void cpu_bringup(void) { @@ -309,7 +310,7 @@ cpu_initialize_context(unsigned int cpu, struct task_st= ruct *idle) * pointing just below where pt_regs would be if it were a normal * kernel entry. */ - ctxt->user_regs.eip =3D (unsigned long)cpu_bringup_and_idle; + ctxt->user_regs.eip =3D (unsigned long)asm_cpu_bringup_and_idle; ctxt->flags =3D VGCF_IN_KERNEL; ctxt->user_regs.eflags =3D 0x1000; /* IOPL_RING1 */ ctxt->user_regs.ds =3D __USER_DS; diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S index d63806e1ff7a..7d1c4fcbe8f7 100644 --- a/arch/x86/xen/xen-head.S +++ b/arch/x86/xen/xen-head.S @@ -58,6 +58,16 @@ SYM_CODE_START(startup_xen) call xen_start_kernel SYM_CODE_END(startup_xen) __FINIT + +#ifdef CONFIG_XEN_PV_SMP +.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 #endif =20 .pushsection .text --=20 2.25.1