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=-9.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS, T_DKIMWL_WL_HIGH,URIBL_BLOCKED,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 88138C04AAB for ; Tue, 7 May 2019 05:41:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4F7F3206A3 for ; Tue, 7 May 2019 05:41:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1557207672; bh=9x7eHrXpvak8eqL0Qp4voPwED6YGX3O6T9ioe5rx+54=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=sWOzC0ExQHaAmT28lCCVbIx/v5lKxjSw6xWKVrOnnsgePPt15sDPIHPfgynWP39Hd EPsJ7JLVuvVz804IRFPcfAQvGaABQ4bi04iuvqtNU/7o0+FFBYhueOa0YfXRCVIAEb uDo2xmuahs6kk0jjBNTmtJ+wmYBvv4pi9bpvWlxY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729275AbfEGFlK (ORCPT ); Tue, 7 May 2019 01:41:10 -0400 Received: from mail.kernel.org ([198.145.29.99]:60530 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728620AbfEGFlF (ORCPT ); Tue, 7 May 2019 01:41:05 -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 DAA9520675; Tue, 7 May 2019 05:41:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1557207663; bh=9x7eHrXpvak8eqL0Qp4voPwED6YGX3O6T9ioe5rx+54=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=j9HV1FzmubExhSyFYjap0PLcTfvGhuDAQ7drpaIRIOcNy7Rm59V5kfHd+W+cTBTYK Lm6sRH41iG7N/hBjLy7U0GpYdmBMfh9fVZadDz/dH8julqnDXGdyviWLnZv5WBMxO3 6B/Ob8x6c3/sS39w+v8sbdYPWpPzVPAOoKe7TQS8= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Sebastian Andrzej Siewior , Borislav Petkov , Rik van Riel , "H. Peter Anvin" , "Jason A. Donenfeld" , Andy Lutomirski , Ard Biesheuvel , Dave Hansen , Ingo Molnar , Nicolai Stange , Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , Thomas Gleixner , kvm ML , linux-efi , x86-ml , Sasha Levin Subject: [PATCH AUTOSEL 4.14 84/95] x86/fpu: Don't export __kernel_fpu_{begin,end}() Date: Tue, 7 May 2019 01:38:13 -0400 Message-Id: <20190507053826.31622-84-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190507053826.31622-1-sashal@kernel.org> References: <20190507053826.31622-1-sashal@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 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: Sebastian Andrzej Siewior [ Upstream commit 12209993e98c5fa1855c467f22a24e3d5b8be205 ] There is one user of __kernel_fpu_begin() and before invoking it, it invokes preempt_disable(). So it could invoke kernel_fpu_begin() right away. The 32bit version of arch_efi_call_virt_setup() and arch_efi_call_virt_teardown() does this already. The comment above *kernel_fpu*() claims that before invoking __kernel_fpu_begin() preemption should be disabled and that KVM is a good example of doing it. Well, KVM doesn't do that since commit f775b13eedee2 ("x86,kvm: move qemu/guest FPU switching out to vcpu_run") so it is not an example anymore. With EFI gone as the last user of __kernel_fpu_{begin|end}(), both can be made static and not exported anymore. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Borislav Petkov Reviewed-by: Rik van Riel Cc: "H. Peter Anvin" Cc: "Jason A. Donenfeld" Cc: Andy Lutomirski Cc: Ard Biesheuvel Cc: Dave Hansen Cc: Ingo Molnar Cc: Nicolai Stange Cc: Paolo Bonzini Cc: Radim Krčmář Cc: Thomas Gleixner Cc: kvm ML Cc: linux-efi Cc: x86-ml Link: https://lkml.kernel.org/r/20181129150210.2k4mawt37ow6c2vq@linutronix.de Signed-off-by: Sasha Levin --- arch/x86/include/asm/efi.h | 6 ++---- arch/x86/include/asm/fpu/api.h | 15 +++++---------- arch/x86/kernel/fpu/core.c | 6 ++---- 3 files changed, 9 insertions(+), 18 deletions(-) diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h index a399c1ebf6f0..96fd0251f8f5 100644 --- a/arch/x86/include/asm/efi.h +++ b/arch/x86/include/asm/efi.h @@ -82,8 +82,7 @@ struct efi_scratch { #define arch_efi_call_virt_setup() \ ({ \ efi_sync_low_kernel_mappings(); \ - preempt_disable(); \ - __kernel_fpu_begin(); \ + kernel_fpu_begin(); \ firmware_restrict_branch_speculation_start(); \ \ if (efi_scratch.use_pgd) { \ @@ -104,8 +103,7 @@ struct efi_scratch { } \ \ firmware_restrict_branch_speculation_end(); \ - __kernel_fpu_end(); \ - preempt_enable(); \ + kernel_fpu_end(); \ }) extern void __iomem *__init efi_ioremap(unsigned long addr, unsigned long size, diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h index a9caac9d4a72..b56d504af654 100644 --- a/arch/x86/include/asm/fpu/api.h +++ b/arch/x86/include/asm/fpu/api.h @@ -12,17 +12,12 @@ #define _ASM_X86_FPU_API_H /* - * Careful: __kernel_fpu_begin/end() must be called with preempt disabled - * and they don't touch the preempt state on their own. - * If you enable preemption after __kernel_fpu_begin(), preempt notifier - * should call the __kernel_fpu_end() to prevent the kernel/user FPU - * state from getting corrupted. KVM for example uses this model. - * - * All other cases use kernel_fpu_begin/end() which disable preemption - * during kernel FPU usage. + * Use kernel_fpu_begin/end() if you intend to use FPU in kernel context. It + * disables preemption so be careful if you intend to use it for long periods + * of time. + * If you intend to use the FPU in softirq you need to check first with + * irq_fpu_usable() if it is possible. */ -extern void __kernel_fpu_begin(void); -extern void __kernel_fpu_end(void); extern void kernel_fpu_begin(void); extern void kernel_fpu_end(void); extern bool irq_fpu_usable(void); diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 2ea85b32421a..2e5003fef51a 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -93,7 +93,7 @@ bool irq_fpu_usable(void) } EXPORT_SYMBOL(irq_fpu_usable); -void __kernel_fpu_begin(void) +static void __kernel_fpu_begin(void) { struct fpu *fpu = ¤t->thread.fpu; @@ -111,9 +111,8 @@ void __kernel_fpu_begin(void) __cpu_invalidate_fpregs_state(); } } -EXPORT_SYMBOL(__kernel_fpu_begin); -void __kernel_fpu_end(void) +static void __kernel_fpu_end(void) { struct fpu *fpu = ¤t->thread.fpu; @@ -122,7 +121,6 @@ void __kernel_fpu_end(void) kernel_fpu_enable(); } -EXPORT_SYMBOL(__kernel_fpu_end); void kernel_fpu_begin(void) { -- 2.20.1