From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S947572AbcJaWTT (ORCPT ); Mon, 31 Oct 2016 18:19:19 -0400 Received: from mail.kernel.org ([198.145.29.136]:39326 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S947523AbcJaWTJ (ORCPT ); Mon, 31 Oct 2016 18:19:09 -0400 From: Andy Lutomirski To: x86@kernel.org Cc: Borislav Petkov , linux-kernel@vger.kernel.org, Rusty Russell , Paolo Bonzini , Rik van Riel , kvm list , Andy Lutomirski Subject: [PATCH 6/8] x86/fpu: #NM without FPU emulation is an error Date: Mon, 31 Oct 2016 15:18:47 -0700 Message-Id: X-Mailer: git-send-email 2.7.4 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org don't use CR0.TS. Make it an error rather than making nonsensical changes to the FPU state. (The cond_local_irq_enable() appears to have been pointless, too.) Signed-off-by: Andy Lutomirski --- arch/x86/kernel/traps.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index bd4e3d4d3625..bf0c6d049080 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -853,6 +853,8 @@ do_spurious_interrupt_bug(struct pt_regs *regs, long error_code) dotraplinkage void do_device_not_available(struct pt_regs *regs, long error_code) { + unsigned long cr0; + RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); #ifdef CONFIG_MATH_EMULATION @@ -866,10 +868,20 @@ do_device_not_available(struct pt_regs *regs, long error_code) return; } #endif - fpu__restore(¤t->thread.fpu); /* interrupts still off */ -#ifdef CONFIG_X86_32 - cond_local_irq_enable(regs); -#endif + + /* This should not happen. */ + cr0 = read_cr0(); + if (WARN(cr0 & X86_CR0_TS, "CR0.TS was set")) { + /* Try to fix it up and carry on. */ + write_cr0(cr0 & ~X86_CR0_TS); + } else { + /* + * Something terrible happened, and we're better off trying + * to kill the task than getting stuck in a never-ending + * loop of #NM faults. + */ + die("unexpected #NM exception", regs, error_code); + } } NOKPROBE_SYMBOL(do_device_not_available); -- 2.7.4