linux-kernel - Re: [RFC PATCH v4 02/27] x86/fpu/xstate: Change some names to separate XSAVES system and user states

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Message-ID: <20180925163745.GC30146@hirez.programming.kicks-ass.net>
Date:   Tue, 25 Sep 2018 18:37:45 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Yu-cheng Yu <yu-cheng.yu@...el.com>
Cc:     x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...capital.net>,
        Balbir Singh <bsingharora@...il.com>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Florian Weimer <fweimer@...hat.com>,
        "H.J. Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>
Subject: Re: [RFC PATCH v4 02/27] x86/fpu/xstate: Change some names to
 separate XSAVES system and user states

On Fri, Sep 21, 2018 at 08:03:26AM -0700, Yu-cheng Yu wrote:

> diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
> index a38bf5a1e37a..f1f9bf91a0ab 100644
> --- a/arch/x86/include/asm/fpu/internal.h
> +++ b/arch/x86/include/asm/fpu/internal.h
> @@ -93,7 +93,8 @@ static inline void fpstate_init_xstate(struct xregs_state *xsave)
>  	 * XRSTORS requires these bits set in xcomp_bv, or it will
>  	 * trigger #GP:
>  	 */
> -	xsave->header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT | xfeatures_mask;
> +	xsave->header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT |
> +			xfeatures_mask_user;

I would be OK with that line extending to 82 characters..

>  }
>  
>  static inline void fpstate_init_fxstate(struct fxregs_state *fx)

> diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
> index 87a57b7642d3..19f8df54c72a 100644
> --- a/arch/x86/kernel/fpu/xstate.c
> +++ b/arch/x86/kernel/fpu/xstate.c

> @@ -421,7 +421,8 @@ static void __init setup_init_fpu_buf(void)
>  	print_xstate_features();
>  
>  	if (boot_cpu_has(X86_FEATURE_XSAVES))
> -		init_fpstate.xsave.header.xcomp_bv = (u64)1 << 63 | xfeatures_mask;
> +		init_fpstate.xsave.header.xcomp_bv =
> +			BIT_ULL(63) | xfeatures_mask_user;

If you do that, the if () needs { } per coding style.

>  
>  	/*
>  	 * Init all the features state with header.xfeatures being 0x0