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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 BF72CC433DF for ; Wed, 8 Jul 2020 15:41:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 91DBC207D0 for ; Wed, 8 Jul 2020 15:41:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594222913; bh=GEJJCDdVm8pUbVjvqKgHBBMZkXtSqzUnyt6nkVra9C4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=2NgWw5GLq+5qyNjzD8i61xfx5oLbW/JmQUY0pXBDRmYfM1RYP9smmfv1rzIarAv1G 6450lgrs/tBlHoreXsWr6xdwCc5hMoAsSmxTGEzAhwwJUiCLNMjuj6s6lCjCwMcfxw YM7I3X1k3k1gwNDg04maYkv3NCYcZDqnKKX45w2c= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730591AbgGHPlw (ORCPT ); Wed, 8 Jul 2020 11:41:52 -0400 Received: from mail.kernel.org ([198.145.29.99]:48644 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730535AbgGHPlo (ORCPT ); Wed, 8 Jul 2020 11:41:44 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1D07220720; Wed, 8 Jul 2020 15:41:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594222903; bh=GEJJCDdVm8pUbVjvqKgHBBMZkXtSqzUnyt6nkVra9C4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=aBUrmeS77HvmBbJ5tE58bgWTympiR5yhdY5uAgV600Sn6deb7x8BxFiS0eY7golBP F6jcC3UivJ8btGG3t7kxEGorLI3O+cQvnMfRFtaYeM3yvNRHOdyji6/DWFCQ9jlHES DMwyC9BGX0f+oimH969clCr9zstSqeaSb7UBJP98= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Petteri Aimonen , Borislav Petkov , Sasha Levin Subject: [PATCH AUTOSEL 5.4 06/16] x86/fpu: Reset MXCSR to default in kernel_fpu_begin() Date: Wed, 8 Jul 2020 11:41:25 -0400 Message-Id: <20200708154135.3199907-6-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200708154135.3199907-1-sashal@kernel.org> References: <20200708154135.3199907-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Petteri Aimonen [ Upstream commit 7ad816762f9bf89e940e618ea40c43138b479e10 ] Previously, kernel floating point code would run with the MXCSR control register value last set by userland code by the thread that was active on the CPU core just before kernel call. This could affect calculation results if rounding mode was changed, or a crash if a FPU/SIMD exception was unmasked. Restore MXCSR to the kernel's default value. [ bp: Carve out from a bigger patch by Petteri, add feature check, add FNINIT call too (amluto). ] Signed-off-by: Petteri Aimonen Signed-off-by: Borislav Petkov Link: https://bugzilla.kernel.org/show_bug.cgi?id=207979 Link: https://lkml.kernel.org/r/20200624114646.28953-2-bp@alien8.de Signed-off-by: Sasha Levin --- arch/x86/include/asm/fpu/internal.h | 5 +++++ arch/x86/kernel/fpu/core.c | 6 ++++++ 2 files changed, 11 insertions(+) diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h index 44c48e34d7994..00eac7f1529b0 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -619,6 +619,11 @@ static inline void switch_fpu_finish(struct fpu *new_fpu) * MXCSR and XCR definitions: */ +static inline void ldmxcsr(u32 mxcsr) +{ + asm volatile("ldmxcsr %0" :: "m" (mxcsr)); +} + extern unsigned int mxcsr_feature_mask; #define XCR_XFEATURE_ENABLED_MASK 0x00000000 diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 12c70840980e4..cd8839027f66d 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -101,6 +101,12 @@ void kernel_fpu_begin(void) copy_fpregs_to_fpstate(¤t->thread.fpu); } __cpu_invalidate_fpregs_state(); + + if (boot_cpu_has(X86_FEATURE_XMM)) + ldmxcsr(MXCSR_DEFAULT); + + if (boot_cpu_has(X86_FEATURE_FPU)) + asm volatile ("fninit"); } EXPORT_SYMBOL_GPL(kernel_fpu_begin); -- 2.25.1