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=-9.8 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_GIT 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 EBCD5C433FF for ; Wed, 14 Aug 2019 10:42:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CCD73214DA for ; Wed, 14 Aug 2019 10:42:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727638AbfHNKmD (ORCPT ); Wed, 14 Aug 2019 06:42:03 -0400 Received: from foss.arm.com ([217.140.110.172]:52008 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727573AbfHNKl7 (ORCPT ); Wed, 14 Aug 2019 06:41:59 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C58AA1597; Wed, 14 Aug 2019 03:41:58 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 056CB3F706; Wed, 14 Aug 2019 03:41:56 -0700 (PDT) From: Mark Rutland To: linux-kernel@vger.kernel.org Cc: ak@linux.intel.com, akpm@linux-foundation.org, bigeasy@linutronix.de, bp@suse.de, catalin.marinas@arm.com, davem@davemloft.net, hch@lst.de, kan.liang@intel.com, mark.rutland@arm.com, mingo@kernel.org, peterz@infradead.org, riel@surriel.com, will@kernel.org Subject: [PATCH 8/9] x86/fpu: correctly check for kthreads Date: Wed, 14 Aug 2019 11:41:30 +0100 Message-Id: <20190814104131.20190-9-mark.rutland@arm.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20190814104131.20190-1-mark.rutland@arm.com> References: <20190814104131.20190-1-mark.rutland@arm.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Per commit: 0cecca9d03c964ab ("x86/fpu: Eager switch PKRU state") ... switch_fpu_state() is trying to distinguish user threads from kthreads, such that kthreads consistently use init_pkru_value. It does do by looking at current->mm. In general, a non-NULL current->mm doesn't imply that current is a kthread, as kthreads can install an mm via use_mm(), and so it's preferable to use is_kthread() to determine whether a thread is a kthread. For consistency, let's use is_kthread() here. Signed-off-by: Mark Rutland Cc: Borislav Petkov Cc: Christoph Hellwig Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Rik van Riel Cc: Sebastian Andrzej Siewior --- arch/x86/include/asm/fpu/internal.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h index 4c95c365058a..ed3d85fa7c67 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -607,7 +607,7 @@ static inline void switch_fpu_finish(struct fpu *new_fpu) * PKRU state is switched eagerly because it needs to be valid before we * return to userland e.g. for a copy_to_user() operation. */ - if (current->mm) { + if (!is_kthread(current)) { pk = get_xsave_addr(&new_fpu->state.xsave, XFEATURE_PKRU); if (pk) pkru_val = pk->pkru; -- 2.11.0