linux-kernel - Re: [PATCH v4 04/10] x86/xsaves: Introduce a new check that allows correct xstates copy from kernel to user directly

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Message-ID: <5727D6B7.6080004@linux.intel.com>
Date:	Mon, 2 May 2016 15:37:43 -0700
From:	Dave Hansen <dave.hansen@...ux.intel.com>
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,
	Andy Lutomirski <luto@...nel.org>,
	Borislav Petkov <bp@...e.de>,
	Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>,
	"Ravi V. Shankar" <ravi.v.shankar@...el.com>,
	Fenghua Yu <fenghua.yu@...el.com>
Subject: Re: [PATCH v4 04/10] x86/xsaves: Introduce a new check that allows
 correct xstates copy from kernel to user directly

On 05/02/2016 03:17 PM, Yu-cheng Yu wrote:
> @@ -167,7 +168,7 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
>  			sizeof(struct user_i387_ia32_struct), NULL,
>  			(struct _fpstate_32 __user *) buf) ? -1 : 1;
>  
> -	if (fpregs_active()) {
> +	if (fpregs_active() || using_compacted_format()) {
>  		/* Save the live register state to the user directly. */
>  		if (copy_fpregs_to_sigframe(buf_fx))
>  			return -1;

So, compared to the first patch, you move the fpregs_active() check out
to the caller of may_copy_fpregs_to_sigframe() (good) and removed a
bunch of comments explaining what was going on (bad).

Do we really want all those comments to die?