From patchwork Mon May 16 20:54:39 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Markus Boehme X-Patchwork-Id: 573686 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1CE7AC433FE for ; Mon, 16 May 2022 21:13:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346473AbiEPVNm (ORCPT ); Mon, 16 May 2022 17:13:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36386 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1350356AbiEPVMZ (ORCPT ); Mon, 16 May 2022 17:12:25 -0400 X-Greylist: delayed 537 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Mon, 16 May 2022 14:04:08 PDT Received: from mout-p-103.mailbox.org (mout-p-103.mailbox.org [IPv6:2001:67c:2050:0:465::103]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 324A940907 for ; Mon, 16 May 2022 14:04:07 -0700 (PDT) Received: from smtp202.mailbox.org (smtp202.mailbox.org [10.196.197.202]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-384) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-103.mailbox.org (Postfix) with ESMTPS id 4L2BN46f6pz9sTG; Mon, 16 May 2022 22:55:16 +0200 (CEST) From: Markus Boehme To: stable@vger.kernel.org Cc: Miroslav Benes , Juergen Gross , Markus Boehme Subject: [PATCH 2/2] x86/xen: Make the secondary CPU idle tasks reliable Date: Mon, 16 May 2022 22:54:39 +0200 Message-Id: <20220516205439.255114-3-markubo@amazon.com> In-Reply-To: <20220516205439.255114-1-markubo@amazon.com> References: <20220516205439.255114-1-markubo@amazon.com> MIME-Version: 1.0 X-MBO-RS-ID: 23f38b479fca7b33fcd X-MBO-RS-META: nf5zz7s37ag36mczewkj1fsq5kjx9s8k Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Miroslav Benes upstream commit c3881eb58d56116c79ac4ee4f40fd15ead124c4b 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 Signed-off-by: Juergen Gross Signed-off-by: Markus Boehme --- 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 64e6ec2c32a7..9d9777ded5f7 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); +void asm_cpu_bringup_and_idle(void); static void cpu_bringup(void) { @@ -310,7 +311,7 @@ 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 deb6abe5d346..591544b4b85a 100644 --- a/arch/x86/xen/xen-head.S +++ b/arch/x86/xen/xen-head.S @@ -58,6 +58,16 @@ ENTRY(startup_xen) call xen_start_kernel 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 .pushsection .text