linux-kernel - Re: [tip:x86/asm] x86/umip: Add emulation code for UMIP instructions

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Date:   Wed, 8 Nov 2017 17:24:04 +0000
From:   Alan Cox <gnomes@...rguk.ukuu.org.uk>
To:     Denys Vlasenko <dvlasenk@...hat.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Peter Anvin <hpa@...or.com>, Borislav Petkov <bp@...e.de>,
        Vlastimil Babka <vbabka@...e.cz>,
        Tony Luck <tony.luck@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        Jonathan Corbet <corbet@....net>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        ricardo.neri-calderon@...ux.intel.com,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Andrew Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>, ray.huang@....com,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Chen Yucong <slaoub@...il.com>, Ingo Molnar <mingo@...nel.org>,
        Jiri Slaby <jslaby@...e.cz>, Shuah Khan <shuah@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "linux-tip-commits@...r.kernel.org\" <linux-tip-commits@...r.kernel.org>"@fuzix.org
Subject: Re: [tip:x86/asm] x86/umip: Add emulation code for UMIP
 instructions

On Wed, 8 Nov 2017 17:53:12 +0100
Denys Vlasenko <dvlasenk@...hat.com> wrote:

> On 11/08/2017 05:34 PM, Linus Torvalds wrote:
> > On Wed, Nov 8, 2017 at 8:14 AM, Denys Vlasenko <dvlasenk@...hat.com> wrote:  
> >>
> >> Can we avoid maintain emulation of these isns, by asking Wine to remove
> >> their use instead?  
> > 
> > If we ask the Wine people to remove the instruction use, that may mean
> > that we can avoid the emulation in four or five _years_ once everybody
> > has updated.
> > 
> > But it wouldn't mean that we could avoid it today.  
> 
> We can postpone enabling UMIP by default by a year or so.
> By this time, new Wine will be on majority of users' machines.

And because Wine compatibility is a bit random at times many users will
have multiple wine versiosn at once on their system which they expect to
continue to work as they used to. For gaming in particularl that isn't
going to change. There are even front ends that let you package up games
with the right matching wine they were tested with.

Alan