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=DKIM_INVALID,DKIM_SIGNED, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, 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 54A25C432C3 for ; Sat, 16 Nov 2019 16:25:34 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 03AD72184B for ; Sat, 16 Nov 2019 16:25:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="fhvBtnvF" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 03AD72184B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 47FgYk1xp8zF46t for ; Sun, 17 Nov 2019 03:25:30 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.org (client-ip=198.145.29.99; helo=mail.kernel.org; envelope-from=sashal@kernel.org; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=kernel.org Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="fhvBtnvF"; dkim-atps=neutral Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 47Ffdg0tsjzF3s9 for ; Sun, 17 Nov 2019 02:43:51 +1100 (AEDT) Received: from sasha-vm.mshome.net (unknown [50.234.116.4]) (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 A843A20729; Sat, 16 Nov 2019 15:43:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573919028; bh=zWF5U4xg7nt3/h5P3T6bRnH5eZb0im/xahs52GP8njM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fhvBtnvFY4od+uheu6kih3XaR6W7n/Go86Vsz12TR2GNvABTY9gldAsbPimX4yH/X VSmdA2afmJ2D15IxbPhL/kxpOCwOHxVwNlyut0+RnekLlzXSY3gG4gqjDcrN2B2lbO jnV/Y+XtUJKQU9xdP42t5d6uKfl/D/ifORnzuhtY= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH AUTOSEL 4.19 126/237] powerpc/process: Fix flush_all_to_thread for SPE Date: Sat, 16 Nov 2019 10:39:21 -0500 Message-Id: <20191116154113.7417-126-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191116154113.7417-1-sashal@kernel.org> References: <20191116154113.7417-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Sasha Levin , Felipe Rechia , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" From: Felipe Rechia [ Upstream commit e901378578c62202594cba0f6c076f3df365ec91 ] Fix a bug introduced by the creation of flush_all_to_thread() for processors that have SPE (Signal Processing Engine) and use it to compute floating-point operations. >>From userspace perspective, the problem was seen in attempts of computing floating-point operations which should generate exceptions. For example: fork(); float x = 0.0 / 0.0; isnan(x); // forked process returns False (should be True) The operation above also should always cause the SPEFSCR FINV bit to be set. However, the SPE floating-point exceptions were turned off after a fork(). Kernel versions prior to the bug used flush_spe_to_thread(), which first saves SPEFSCR register values in tsk->thread and then calls giveup_spe(tsk). After commit 579e633e764e, the save_all() function was called first to giveup_spe(), and then the SPEFSCR register values were saved in tsk->thread. This would save the SPEFSCR register values after disabling SPE for that thread, causing the bug described above. Fixes 579e633e764e ("powerpc: create flush_all_to_thread()") Signed-off-by: Felipe Rechia Signed-off-by: Michael Ellerman Signed-off-by: Sasha Levin --- arch/powerpc/kernel/process.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 909c9407e392a..02b69a68139cc 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -575,12 +575,11 @@ void flush_all_to_thread(struct task_struct *tsk) if (tsk->thread.regs) { preempt_disable(); BUG_ON(tsk != current); - save_all(tsk); - #ifdef CONFIG_SPE if (tsk->thread.regs->msr & MSR_SPE) tsk->thread.spefscr = mfspr(SPRN_SPEFSCR); #endif + save_all(tsk); preempt_enable(); } -- 2.20.1