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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham 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 3F01DC282CE for ; Tue, 4 Jun 2019 17:54:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 111692075B for ; Tue, 4 Jun 2019 17:54:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726464AbfFDRyj (ORCPT ); Tue, 4 Jun 2019 13:54:39 -0400 Received: from verein.lst.de ([213.95.11.211]:37806 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726295AbfFDRyj (ORCPT ); Tue, 4 Jun 2019 13:54:39 -0400 Received: by newverein.lst.de (Postfix, from userid 2407) id 2EF3368B05; Tue, 4 Jun 2019 19:54:12 +0200 (CEST) Date: Tue, 4 Jun 2019 19:54:12 +0200 From: Christoph Hellwig To: x86@kernel.org Cc: Sebastian Andrzej Siewior , linux-kernel@vger.kernel.org Subject: [PATCH 4/3] x86/fpu: don't use current->mm to check for a kthread Message-ID: <20190604175411.GA27477@lst.de> References: <20190604071524.12835-1-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190604071524.12835-1-hch@lst.de> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org current->mm can be non-NULL if a kthread calls use_mm. Check for PF_KTHREAD instead to decide when to store user mode FP state. Fixes: 2722146eb784 ("x86/fpu: Remove fpu->initialized") Reported-by: Peter Zijlstra Signed-off-by: Christoph Hellwig --- arch/x86/include/asm/fpu/internal.h | 6 +++--- arch/x86/kernel/fpu/core.c | 3 ++- 2 files changed, 5 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h index 9e27fa05a7ae..4c95c365058a 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -536,7 +536,7 @@ static inline void __fpregs_load_activate(void) struct fpu *fpu = ¤t->thread.fpu; int cpu = smp_processor_id(); - if (WARN_ON_ONCE(current->mm == NULL)) + if (WARN_ON_ONCE(current->flags & PF_KTHREAD)) return; if (!fpregs_state_valid(fpu, cpu)) { @@ -567,11 +567,11 @@ static inline void __fpregs_load_activate(void) * otherwise. * * The FPU context is only stored/restored for a user task and - * ->mm is used to distinguish between kernel and user threads. + * PF_KTHREAD is used to distinguish between kernel and user threads. */ static inline void switch_fpu_prepare(struct fpu *old_fpu, int cpu) { - if (static_cpu_has(X86_FEATURE_FPU) && current->mm) { + if (static_cpu_has(X86_FEATURE_FPU) && !(current->flags & PF_KTHREAD)) { if (!copy_fpregs_to_fpstate(old_fpu)) old_fpu->last_cpu = -1; else diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 5e0240d029fd..12c70840980e 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -91,7 +91,8 @@ void kernel_fpu_begin(void) this_cpu_write(in_kernel_fpu, true); - if (current->mm && !test_thread_flag(TIF_NEED_FPU_LOAD)) { + if (!(current->flags & PF_KTHREAD) && + !test_thread_flag(TIF_NEED_FPU_LOAD)) { set_thread_flag(TIF_NEED_FPU_LOAD); /* * Ignore return value -- we don't care if reg state -- 2.20.1