From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751308AbdAWRXa (ORCPT ); Mon, 23 Jan 2017 12:23:30 -0500 Received: from mga01.intel.com ([192.55.52.88]:51433 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750966AbdAWRX3 (ORCPT ); Mon, 23 Jan 2017 12:23:29 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.33,274,1477983600"; d="scan'208";a="1097840988" Subject: Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a XSAVES area To: Yu-cheng Yu References: <1485075023-30161-1-git-send-email-haokexin@gmail.com> <20170123165529.GA4996@test-lenovo> Cc: fenghua.yu@intel.com, dvlasenk@redhat.com, peterz@infradead.org, oleg@redhat.com, mingo@kernel.org, linux-kernel@vger.kernel.org, brgerst@gmail.com, luto@kernel.org, bp@alien8.de, jpoimboe@redhat.com, haokexin@gmail.com, hpa@zytor.com, quentin.casasnovas@oracle.com, tglx@linutronix.de, torvalds@linux-foundation.org, riel@redhat.com, linux-tip-commits@vger.kernel.org From: Dave Hansen Message-ID: <2be814b7-9fd6-7955-b4e3-6ecb4ef76052@linux.intel.com> Date: Mon, 23 Jan 2017 09:23:06 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 MIME-Version: 1.0 In-Reply-To: <20170123165529.GA4996@test-lenovo> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/23/2017 08:55 AM, Yu-cheng Yu wrote: > On Mon, Jan 23, 2017 at 07:36:20AM -0800, Dave Hansen wrote: >> The kernel xsave buffer should *ALWAYS* have the >> XCOMP_BV_COMPACTED_FORMAT bit set. It should have been set before the >> copyin and it should be set when it's finished. >> >> The best fix here would be not to paper over the issue in the copy >> function but find where it got clobbered, or where some initialization >> code failed to set it. > > Someone else reported different issues from the same bug and a different > patch was just tested OK this morning. I think that adding xfeatures bits > to xcomp_bv should have been done in fpstate_init(). Right. So where did it get cleared out? > Also, in copy_init_fpstate_to_fpregs(), we do: > > copy_kernel_to_xregs(&init_fpstate.xsave, -1). > > That (-1) could mean (0) because the parameters are declared as: > > copy_kernel_to_xregs(struct xregs_state *, u64) I'm not sure what you're saying. -1 just means "all 1's" when cast to an unsigned type. This shouldn't case any problems.