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Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init

From "H. Peter Anvin" <hpa@zytor.com>
Newsgroups linux.kernel
Subject Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init
Date 2016-01-18 20:50 +0100
Message-ID <qSnYl-5eq-9@gated-at.bofh.it> (permalink)
References (3 earlier) <qRSUx-1gy-15@gated-at.bofh.it> <qSljR-3pb-13@gated-at.bofh.it> <qSmzg-4r1-13@gated-at.bofh.it> <qSmIW-4vc-15@gated-at.bofh.it> <qSmSD-4zc-25@gated-at.bofh.it>
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On 01/18/16 10:39, Borislav Petkov wrote:
> On Mon, Jan 18, 2016 at 10:29:24AM -0800, Andy Lutomirski wrote:
>> I think that, if we can make static_cpu_has be unconditionally safe as
>> a result
> 
> Problem with this is the additional .altinstructions entry for
> X86_FEATURE_ALWAYS. And sometimes you don't really need to use the _safe
> variant when you know you're safe.
> 

I think the two-byte optimization is the real issue if there is one at
all.  I don't care about the inittext, and unless I'm misremembering
completely altinstructions also get ejected.

So I don't personally object to killing off the unsafe variant.

	-hpa

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Thread

[PATCH] x86: static_cpu_has_safe: discard dynamic check after init Brian Gerst <brgerst@gmail.com> - 2016-01-16 20:30 +0100
  Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init Borislav Petkov <bp@suse.de> - 2016-01-16 20:40 +0100
    Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Brian Gerst <brgerst@gmail.com> - 2016-01-16 21:00 +0100
      Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init Borislav Petkov <bp@suse.de> - 2016-01-17 11:40 +0100
        Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Brian Gerst <brgerst@gmail.com> - 2016-01-18 18:00 +0100
          Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Andy Lutomirski <luto@amacapital.net> - 2016-01-18 18:50 +0100
          Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init Borislav Petkov <bp@suse.de> - 2016-01-18 19:20 +0100
            Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Andy Lutomirski <luto@amacapital.net> - 2016-01-18 19:30 +0100
              Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init Borislav Petkov <bp@suse.de> - 2016-01-18 19:40 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-18 20:50 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init Borislav Petkov <bp@suse.de> - 2016-01-19 00:10 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-19 00:20 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init Borislav Petkov <bp@suse.de> - 2016-01-19 00:30 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init Borislav Petkov <bp@suse.de> - 2016-01-19 15:00 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init Borislav Petkov <bp@suse.de> - 2016-01-19 17:30 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init Borislav Petkov <bp@suse.de> - 2016-01-20 00:20 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Andy Lutomirski <luto@amacapital.net> - 2016-01-20 00:30 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Boris Petkov <bp@suse.de> - 2016-01-20 01:00 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-20 05:10 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init Borislav Petkov <bp@suse.de> - 2016-01-20 11:40 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-20 11:50 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init Borislav Petkov <bp@suse.de> - 2016-01-21 23:20 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-21 23:30 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init Borislav Petkov <bp@suse.de> - 2016-01-22 00:00 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-22 00:40 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-22 00:40 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init Borislav Petkov <bp@suse.de> - 2016-01-22 11:40 +0100
            Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init Borislav Petkov <bp@suse.de> - 2016-01-18 20:00 +0100
              Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init Borislav Petkov <bp@suse.de> - 2016-01-19 02:20 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-19 02:40 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init Borislav Petkov <bp@suse.de> - 2016-01-19 10:30 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-20 05:10 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Brian Gerst <brgerst@gmail.com> - 2016-01-20 05:40 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-20 05:50 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-20 12:00 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init Borislav Petkov <bp@suse.de> - 2016-01-20 12:10 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-20 15:50 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init Borislav Petkov <bp@suse.de> - 2016-01-20 12:00 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init Borislav Petkov <bp@suse.de> - 2016-01-20 16:10 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-20 16:20 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init Borislav Petkov <bp@suse.de> - 2016-01-20 17:10 +0100
                Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after  init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-20 17:20 +0100

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