linux-kernel - Re: [PATCH 1/5] x86/ibrs: Introduce native_rdmsrl, and native

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Message-ID: <20180112030139.GA46095@otc-nc-03>
Date:   Thu, 11 Jan 2018 19:01:40 -0800
From:   "Raj, Ashok" <ashok.raj@...el.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Arjan Van De Ven <arjan.van.de.ven@...el.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Peter Zijlstra <peterz@...radead.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jun Nakajima <jun.nakajima@...el.com>,
        Asit Mallick <asit.k.mallick@...el.com>, ashok.raj@...el.com
Subject: Re: [PATCH 1/5] x86/ibrs: Introduce native_rdmsrl, and native_wrmsrl

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@...el.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.