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Subject: Re: [PATCH v4 04/10] x86/xsaves: Introduce a new check that allows
 correct xstates copy from kernel to user directly
To: Yu-cheng Yu <yu-cheng.yu@intel.com>
References: <5723FE20.7000906@linux.intel.com>
 <20160502155734.GA21577@test-lenovo> <57277B11.9080802@linux.intel.com>
 <20160502163410.GA21734@test-lenovo> <572783C3.8040907@linux.intel.com>
 <20160502171936.GA22224@test-lenovo> <57278F56.6050600@linux.intel.com>
 <20160502211817.GA22492@test-lenovo> <20160502212449.GA22532@test-lenovo>
 <5727C75E.8000401@linux.intel.com> <20160502221754.GA22667@test-lenovo>
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, Andy Lutomirski <luto@kernel.org>,
        Borislav Petkov <bp@suse.de>,
        Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>,
        "Ravi V. Shankar" <ravi.v.shankar@intel.com>,
        Fenghua Yu <fenghua.yu@intel.com>
From: Dave Hansen <dave.hansen@linux.intel.com>
Message-ID: <5727D6B7.6080004@linux.intel.com>
Date: Mon, 2 May 2016 15:37:43 -0700
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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?