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Re: [PATCH 2/9] x86/fpu: Hard-disable lazy fpu mode

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On 05/10/2016 02:34, riel@redhat.com wrote:
> From: Andy Lutomirski <luto@kernel.org>
> 
> Since commit 58122bf1d856 ("x86/fpu: Default eagerfpu=on on all
> CPUs") in Linux 4.6, eager FPU mode has been the default on all x86
> systems, and no one has reported any regressions.
> 
> This patch removes the ability to enable lazy mode: use_eager_fpu()
> becomes "return true" and all of the FPU mode selection machinery is
> removed.

I haven't quite followed up on my promise to benchmark lazy vs. eager
FPU, but I probably should do that now...

I see two possible issues with this.  First, AMD as far as I know does
not have XSAVEOPT.  Second, when using virtualization, depending on how
you configure your cluster it's enough to have one pre-SandyBridge Intel
machine to force no XSAVE on all machines.

Thanks,

Paolo

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[PATCH 2/9] x86/fpu: Hard-disable lazy fpu mode riel@redhat.com - 2016-10-05 02:40 +0200
  Re: [PATCH 2/9] x86/fpu: Hard-disable lazy fpu mode Paolo Bonzini <pbonzini@redhat.com> - 2016-10-05 09:20 +0200
    Re: [PATCH 2/9] x86/fpu: Hard-disable lazy fpu mode Rik van Riel <riel@redhat.com> - 2016-10-05 16:00 +0200
      Re: [PATCH 2/9] x86/fpu: Hard-disable lazy fpu mode Paolo Bonzini <pbonzini@redhat.com> - 2016-10-05 16:10 +0200
        Re: [PATCH 2/9] x86/fpu: Hard-disable lazy fpu mode Andy Lutomirski <luto@amacapital.net> - 2016-10-05 18:10 +0200
          Re: [PATCH 2/9] x86/fpu: Hard-disable lazy fpu mode Paolo Bonzini <pbonzini@redhat.com> - 2016-10-05 18:20 +0200
  [tip:x86/fpu] x86/fpu: Hard-disable lazy FPU mode tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2016-10-07 11:50 +0200

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