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

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Message-ID: <0575AF4FD06DD142AD198903C74E1CC87A5C7FB4@FMSMSX151.amr.corp.intel.com>
Date:   Sat, 13 Jan 2018 13:52:24 +0000
From:   "Van De Ven, Arjan" <arjan.van.de.ven@...el.com>
To:     Andy Lutomirski <luto@...nel.org>,
        "Hansen, Dave" <dave.hansen@...el.com>
CC:     "Raj, Ashok" <ashok.raj@...el.com>,
        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>,
        Andrea Arcangeli <aarcange@...hat.com>,
        "Andi Kleen" <ak@...ux.intel.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        "Peter Zijlstra" <peterz@...radead.org>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "Nakajima, Jun" <jun.nakajima@...el.com>,
        "Mallick, Asit K" <asit.k.mallick@...el.com>
Subject: RE: [PATCH 1/5] x86/ibrs: Introduce native_rdmsrl, and native_wrmsrl


> > We were also worried about the indirect calls that are part of the
> > paravirt interfaces when retpolines are not in place.
> >
> 
> How could those possibly be any worse than any other indirect call in
> the kernel?

they're worse if they happen before you write the MSR that then protects them?