Re: [PATCH v2] x86/fpu: copy MXCSR & MXCSR_FLAGS with SSE/YMM state

From	Yu-cheng Yu <yu-cheng.yu@intel.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2] x86/fpu: copy MXCSR & MXCSR_FLAGS with SSE/YMM state
Date	2017-02-10 02:30 +0100
Message-ID	<t97SN-58a-3@gated-at.bofh.it> (permalink)
References	<t96N4-4gQ-23@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Thu, Feb 09, 2017 at 06:43:47PM -0500, Rik van Riel wrote:
>  /*
> + * Weird legacy quirk: SSE and YMM states store information in the
> + * MXCSR and MXCSR_FLAGS fields of the FP area. That means if the FP
> + * area is marked as unused in the xfeatures header, we need to copy
> + * MXCSR and MXCSR_FLAGS if either SSE or YMM are in use.
> + */
> +static inline bool xfeatures_need_mxcsr_copy(u64 xfeatures)
> +{
> +	if (!(xfeatures & (XFEATURE_MASK_SSE|XFEATURE_MASK_YMM)))
> +		return 0;
> +
> +	if (xfeatures & XFEATURE_MASK_FP)
> +		return 0;
> +
> +	return 1;
> +}

Would you consider separating MXCSR & MXCSR_FLAGS from
XFEATURE_MASK_FP.  Here we assume if both xstate[0] and xstate[1]
are being copied, then there is no need to copy MXCSR/MXCSR_FLAGS
again.  What if only xstate[0] is copied and MXCSR/MXCSR_FLAGS
is invalid?

Yu-cheng

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[PATCH v2] x86/fpu: copy MXCSR & MXCSR_FLAGS with SSE/YMM state Rik van Riel <riel@redhat.com> - 2017-02-10 01:00 +0100
  Re: [PATCH v2] x86/fpu: copy MXCSR & MXCSR_FLAGS with SSE/YMM state Borislav Petkov <bp@suse.de> - 2017-02-10 01:10 +0100
    Re: [PATCH v2] x86/fpu: copy MXCSR & MXCSR_FLAGS with SSE/YMM state Rik van Riel <riel@redhat.com> - 2017-02-10 02:20 +0100
      Re: [PATCH v2] x86/fpu: copy MXCSR & MXCSR_FLAGS with SSE/YMM state Ingo Molnar <mingo@kernel.org> - 2017-02-10 09:10 +0100
        [PATCH v3] x86/fpu: copy MXCSR & MXCSR_FLAGS with SSE/YMM state Rik van Riel <riel@redhat.com> - 2017-02-10 15:30 +0100
          Re: [PATCH v3] x86/fpu: copy MXCSR & MXCSR_FLAGS with SSE/YMM state Ingo Molnar <mingo@kernel.org> - 2017-02-11 11:10 +0100
  Re: [PATCH v2] x86/fpu: copy MXCSR & MXCSR_FLAGS with SSE/YMM state Rik van Riel <riel@redhat.com> - 2017-02-10 02:10 +0100
    Re: [PATCH v2] x86/fpu: copy MXCSR & MXCSR_FLAGS with SSE/YMM state Yu-cheng Yu <yu-cheng.yu@intel.com> - 2017-02-10 19:30 +0100
  Re: [PATCH v2] x86/fpu: copy MXCSR & MXCSR_FLAGS with SSE/YMM state Yu-cheng Yu <yu-cheng.yu@intel.com> - 2017-02-10 02:30 +0100

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