From mboxrd@z Thu Jan  1 00:00:00 1970
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1754620AbeAMGUU (ORCPT <rfc822;ralf@linux-mips.org> + 1 other);
        Sat, 13 Jan 2018 01:20:20 -0500
Received: from mail.kernel.org ([198.145.29.99]:33998 "EHLO mail.kernel.org"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1750732AbeAMGUT (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Sat, 13 Jan 2018 01:20:19 -0500
DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1A1B62177C
Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org
Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=luto@kernel.org
X-Google-Smtp-Source: ACJfBovQZjOx7VgVz+6Svho86fLlAwN0x3TYHf+pIyoh2cVg0bMzXKBVLCywPj3nAyhKxqpm0ehL5FMfx/GvWrxh7sk=
MIME-Version: 1.0
In-Reply-To: <20180112030139.GA46095@otc-nc-03>
References: <1515720739-43819-1-git-send-email-ashok.raj@intel.com>
 <1515720739-43819-2-git-send-email-ashok.raj@intel.com> <CALCETrWy_bTMrkcJfmPu=5dmRnSmKYCDp3+62CPgP1BKiV6U2g@mail.gmail.com>
 <20180112015231.GA44418@otc-nc-03> <CALCETrX4qi_O4e=iEQRVm1uUqUS6QXBhSLwrpXr6fmK9vLhq7Q@mail.gmail.com>
 <20180112030139.GA46095@otc-nc-03>
From: Andy Lutomirski <luto@kernel.org>
Date: Fri, 12 Jan 2018 22:19:57 -0800
X-Gmail-Original-Message-ID: <CALCETrWN8pta15d34bYb3-bhebB9P8nh+Aj8CL14J=6vycLLXw@mail.gmail.com>
Message-ID: <CALCETrWN8pta15d34bYb3-bhebB9P8nh+Aj8CL14J=6vycLLXw@mail.gmail.com>
Subject: Re: [PATCH 1/5] x86/ibrs: Introduce native_rdmsrl, and native_wrmsrl
To: "Raj, Ashok" <ashok.raj@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Greg KH <gregkh@linuxfoundation.org>,
        Dave Hansen <dave.hansen@intel.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Andi Kleen <ak@linux.intel.com>,
        Arjan Van De Ven <arjan.van.de.ven@intel.com>,
        David Woodhouse <dwmw@amazon.co.uk>,
        Peter Zijlstra <peterz@infradead.org>,
        Dan Williams <dan.j.williams@intel.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Jun Nakajima <jun.nakajima@intel.com>,
        Asit Mallick <asit.k.mallick@intel.com>
Content-Type: text/plain; charset="UTF-8"
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 11, 2018 at 7:01 PM, Raj, Ashok <ashok.raj@intel.com> wrote:
> On Thu, Jan 11, 2018 at 06:20:13PM -0800, Andy Lutomirski wrote:
>> On Thu, Jan 11, 2018 at 5:52 PM, Raj, Ashok <ashok.raj@intel.com> wrote:
>> >>
>> >> What's wrong with native_read_msr()?
>> >
>> > Yes, i think i should have added to msr.h. The names didn't read as a
>> > pair, one was native_read_msr, wrmsrl could be taken over when paravirt is
>> > defined?
>>
>> Why do you need to override paravirt?
>
> The idea was since these MSR's are passed through we shouldn't need to
> handle them any differently. Also its best to do this as soon as possible
> and avoid longer paths to get this barrier to hardware.
>

It should end up with essentially the same instructions at runtime.
I'm generally in favor of using the less weird code when it will work.