From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1751442AbcEJRbl (ORCPT <rfc822;w@1wt.eu>);
	Tue, 10 May 2016 13:31:41 -0400
Received: from mga01.intel.com ([192.55.52.88]:21204 "EHLO mga01.intel.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1751033AbcEJRbk (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Tue, 10 May 2016 13:31:40 -0400
X-ExtLoop1: 1
X-IronPort-AV: E=Sophos;i="5.24,605,1455004800"; 
   d="scan'208";a="803215958"
Subject: Re: [PATCH v5 02/13] x86/xsaves: Rename xstate_size to
 kernel_xstate_size to explicitly distinguish xstate size in kernel from user
 space
To: Borislav Petkov <bp@suse.de>
References: <cover.1462816638.git.yu-cheng.yu@intel.com>
 <c7710a66feae49c81347402baf86d18fe0718610.1462816638.git.yu-cheng.yu@intel.com>
 <20160510170130.GE28520@pd.tnic> <5732159C.6030202@linux.intel.com>
 <20160510172657.GF28520@pd.tnic>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>, linux-kernel@vger.kernel.org,
        x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        Andy Lutomirski <luto@kernel.org>,
        Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>,
        "Ravi V. Shankar" <ravi.v.shankar@intel.com>,
        Fenghua Yu <fenghua.yu@intel.com>
From: Dave Hansen <dave.hansen@linux.intel.com>
Message-ID: <57321AFA.3020104@linux.intel.com>
Date: Tue, 10 May 2016 10:31:38 -0700
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101
 Thunderbird/38.6.0
MIME-Version: 1.0
In-Reply-To: <20160510172657.GF28520@pd.tnic>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 05/10/2016 10:26 AM, Borislav Petkov wrote:
>> > It's nice to dump out interesting data in dmesg, but I'm curious why you
>> > think it's interesting.
> I think it would be interesting to know what the kernel's idea
> is of user_xstate_size. I know, I know, one can follow the code
> and figure out what it is but one can say the same about a lot of
> other "interesting" data dumped in dmesg. And I'd like to know what
> fpu__init_system_xstate_size_legacy() decided. And so I know how many
> data is shuffled to/from userspace.
> 
> And btw, this message needs more "humanization":
> 
> [    0.000000] x86/fpu: xstate_offset[2]:  576, xstate_sizes[2]:  256
> 
> That doesn't tell me anything.
> 
> Oh and it can be read out from CPUID too.

That all sounds like great stuff to do in a follow-on patchset after
this XSAVES stuff.