Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1751726AbeAENcO (ORCPT <rfc822;ralf@linux-mips.org> + 1 other);
        Fri, 5 Jan 2018 08:32:14 -0500
Received: from mail.linuxfoundation.org ([140.211.169.12]:58732 "EHLO
        mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1751279AbeAENcN (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Fri, 5 Jan 2018 08:32:13 -0500
Date: Fri, 5 Jan 2018 14:32:17 +0100
From: Greg KH <gregkh@linuxfoundation.org>
To: Borislav Petkov <bp@alien8.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Andy Lutomirski <luto@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Dave Hansen <dave.hansen@intel.com>,
        Andi Kleen <ak@linux.intel.com>,
        Arjan Van De Ven <arjan.van.de.ven@intel.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 7/7] x86/microcode: Recheck IBRS features on microcode
 reload
Message-ID: <20180105133217.GB12036@kroah.com>
References: <cover.1515086770.git.tim.c.chen@linux.intel.com>
 <a2092889d6d2198494d97a341ea0375a95d3b3bd.1515086770.git.tim.c.chen@linux.intel.com>
 <20180104182858.2nevvgeq5wdojz2w@pd.tnic>
 <20180104183430.GJ13348@redhat.com>
 <20180104185033.tsbijx32as6wqvye@pd.tnic>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20180104185033.tsbijx32as6wqvye@pd.tnic>
User-Agent: Mutt/1.9.2 (2017-12-15)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Return-Path: <linux-kernel-owner@vger.kernel.org>

On Thu, Jan 04, 2018 at 07:50:33PM +0100, Borislav Petkov wrote:
> On Thu, Jan 04, 2018 at 07:34:30PM +0100, Andrea Arcangeli wrote:
> > void spec_ctrl_rescan_cpuid(void)
> > {
> > 	int cpu;
> > 
> > 	if (use_ibp_disable)
> > 		return;
> > 	mutex_lock(&spec_ctrl_mutex);
> > 	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL ||
> > 	    boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
> > 		/* detect spec ctrl related cpuid additions */
> > 		init_scattered_cpuid_features(&boot_cpu_data);
> 
> You don't need to noodle through all the scattered features - just the
> two bits.

Does it really matter?  Rescanning everything can't hurt here, and it
shouldn't be noticable in any boot time chart.  I feel like arguing
about tiny stuff like this takes away from the obvious other problems
this whole patch series had :(

But hey, I'm guilty of it numerous times as well, I know, so I'll shut
up now...

thanks,

greg k-h