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Re: [PATCH RFC 1/3] fpu/x86: add make_fpregs_active(_newstate) helper functions

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On Mon, Oct 17, 2016 at 4:04 PM, Yu-cheng Yu <yu-cheng.yu@intel.com> wrote:
> On Mon, Oct 17, 2016 at 01:57:06PM -0700, Andy Lutomirski wrote:
>> Dave and/or Yu-cheng: didn't one of you have some code to allow a user
>> xstate buffer to be filled from the copy in kernel memory?  If we did
>> that, we could avoid this mess entirely.
>
> In copy_fpstate_to_sigframe() (arch/x86/kernel/fpu/signal.c), the
> assumption was we have lazy fpu:
>
>         if (fpregs_active() || we want an #NM exception)
>                 copy_fpregs_to_sigframe();
>         else
>                 copy kernel buffer to user buffer;
>
> But this is not the true anymore.  Or do you mean something else?

Rik wants to add a different form of FPU laziness, and it would be
simpler if we could just always copy from a kernel buffer.  Does code
to do that exist in the tree?

--Andy

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[PATCH RFC 1/3] fpu/x86: add make_fpregs_active(_newstate) helper functions riel@redhat.com - 2016-10-17 22:20 +0200
  Re: [PATCH RFC 1/3] fpu/x86: add make_fpregs_active(_newstate) helper functions Andy Lutomirski <luto@amacapital.net> - 2016-10-17 23:00 +0200
    Re: [PATCH RFC 1/3] fpu/x86: add make_fpregs_active(_newstate)  helper functions Yu-cheng Yu <yu-cheng.yu@intel.com> - 2016-10-18 01:10 +0200
      Re: [PATCH RFC 1/3] fpu/x86: add make_fpregs_active(_newstate) helper functions Andy Lutomirski <luto@amacapital.net> - 2016-10-18 01:40 +0200
        Re: [PATCH RFC 1/3] fpu/x86: add make_fpregs_active(_newstate)  helper functions Yu-cheng Yu <yu-cheng.yu@intel.com> - 2016-10-18 01:50 +0200
          Re: [PATCH RFC 1/3] fpu/x86: add make_fpregs_active(_newstate) helper functions Andy Lutomirski <luto@amacapital.net> - 2016-10-18 03:30 +0200

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