Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Mon, 29 Jan 2018 19:13:40 -0800
From:   Andi Kleen <ak@linux.intel.com>
To:     Jim Mattson <jmattson@google.com>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        David Woodhouse <dwmw2@infradead.org>,
        Arjan van de Ven <arjan@linux.intel.com>,
        Eduardo Habkost <ehabkost@redhat.com>,
        KarimAllah Ahmed <karahmed@amazon.de>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Andy Lutomirski <luto@kernel.org>,
        Ashok Raj <ashok.raj@intel.com>,
        Asit Mallick <asit.k.mallick@intel.com>,
        Borislav Petkov <bp@suse.de>,
        Dan Williams <dan.j.williams@intel.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "H . Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
        Janakarajan Natarajan <Janakarajan.Natarajan@amd.com>,
        Joerg Roedel <joro@8bytes.org>,
        Jun Nakajima <jun.nakajima@intel.com>,
        Laura Abbott <labbott@redhat.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        KVM list <kvm@vger.kernel.org>,
        the arch/x86 maintainers <x86@kernel.org>,
        "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Subject: Re: [RFC,05/10] x86/speculation: Add basic IBRS support
 infrastructure
Message-ID: <20180130031340.GV26209@tassilo.jf.intel.com>
References: <1516476182-5153-6-git-send-email-karahmed@amazon.de>
 <20180129201404.GA1588@localhost.localdomain>
 <1517257022.18619.30.camel@infradead.org>
 <20180129204256.GV25150@localhost.localdomain>
 <31415b7f-9c76-c102-86cd-6bf4e23e3aee@linux.intel.com>
 <1517259759.18619.38.camel@infradead.org>
 <CA+55aFxBh3LvsQq9wy313NQCn3iu+yuAmsi0zNVxWmGDUUds-A@mail.gmail.com>
 <CALMp9eSM6WqX5wstMPgx64d+Dwh4A9+9ngf70qjDVx-_2_g4WQ@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CALMp9eSM6WqX5wstMPgx64d+Dwh4A9+9ngf70qjDVx-_2_g4WQ@mail.gmail.com>
User-Agent: Mutt/1.9.1 (2017-09-22)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

> Right now, we are dealing with one workaround, which is tied to
> Skylake-era model numbers. Yes, we could report a Skylake model
> number, and Linux guests would use IBRS instead of retpoline. But this

Nobody is planning to use IBRS and Linus has rejected it.

> approach doesn't scale. What happens when someone introduces a
> workaround tied to some other model numbers?

There are already many of those in the tree for other issues and features. 
So far you managed to survive without. Likely that will be true
in the future too.

-Andi