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Date:   Tue, 25 Sep 2018 19:03:55 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Yu-cheng Yu <yu-cheng.yu@intel.com>
Cc:     x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-mm@kvack.org,
        linux-arch@vger.kernel.org, linux-api@vger.kernel.org,
        Arnd Bergmann <arnd@arndb.de>,
        Andy Lutomirski <luto@amacapital.net>,
        Balbir Singh <bsingharora@gmail.com>,
        Cyrill Gorcunov <gorcunov@gmail.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Florian Weimer <fweimer@redhat.com>,
        "H.J. Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Kees Cook <keescook@chromium.org>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Nadav Amit <nadav.amit@gmail.com>,
        Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
        Randy Dunlap <rdunlap@infradead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@intel.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>
Subject: Re: [RFC PATCH v4 03/27] x86/fpu/xstate: Enable XSAVES system states
Message-ID: <20180925170355.GD30146@hirez.programming.kicks-ass.net>
References: <20180921150351.20898-1-yu-cheng.yu@intel.com>
 <20180921150351.20898-4-yu-cheng.yu@intel.com>
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On Fri, Sep 21, 2018 at 08:03:27AM -0700, Yu-cheng Yu wrote:
> diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
> index 4bd56079048f..9f51b0e1da25 100644
> --- a/arch/x86/kernel/fpu/core.c
> +++ b/arch/x86/kernel/fpu/core.c
> @@ -365,8 +365,13 @@ void fpu__drop(struct fpu *fpu)
>   */
>  static inline void copy_init_user_fpstate_to_fpregs(void)
>  {
> +	/*
> +	 * Only XSAVES user states are copied.
> +	 * System states are preserved.
> +	 */
>  	if (use_xsave())
> -		copy_kernel_to_xregs(&init_fpstate.xsave, -1);
> +		copy_kernel_to_xregs(&init_fpstate.xsave,
> +				     xfeatures_mask_user);

By my counting, that doesn't qualify for a line-break, it hits 80.

If you were to do this line-break, coding style would have you liberally
sprinkle {} around.

>  	else if (static_cpu_has(X86_FEATURE_FXSR))
>  		copy_kernel_to_fxregs(&init_fpstate.fxsave);
>  	else